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Glossary

Note: The entries in this book are organized primarily by the type of anatomical feature, and alphabetized principal word by principal word, without regard to punctuation or connectives. For example, the user who is looking for the cochlear nerve should look under “nerve, cochlea,” and the user who is looking for the tract of Barnes should look between “tract, Arnold’s” and “tract, Burdach’s.”

Biographical entries are listed by last name, and frequently refer the user to anatomical features associated with each historical figure.

The author is aware that the user will often see a phrase from a different perspective, and has tried to supply enough cross references to facilitate use without extensive repetition of definitions.

a

A-fiber heavily medullated, fast conducting nerve fiber, as large as 22 µm in diameter.

aberrant pyramidal pyramidal [i.e., corticospinal and other corticofugal axons] that do not travel in the pyramids.

acalculia inability to complete simple arithmetical problems, associated with injuries in the region of the supramarginal gyrus of the dominant cerebral hemisphere.

accommodation adaptation of the eye for near vision.

acervulus calcareous body in the pineal body. Syn: brain sand.

acetylcholine neurotransmitter released at nerve endings during transmission of a nerve impulse, at motor end-plates in skeletal muscle, at postganglionic parasympathetic endings, at postganglionic sympathetic endings on sweat glands, and at synapses in parts of the central nervous system and in autonomic ganglia.

ACh see acetylcholine.

Achillini, Alessandro [1463–1512] anatomist of Bologna who made original observations on the hippocampus.

acoustic pertaining to the ear. For acoustic nerve, tubercle, see the nouns.

Adamkiewicz, Albert [1850–1921] Austrian pathologist noted for his description of the crescent-shaped cells under the neurolemma of medullated nerve fibers, and for the first extensive study on the blood vessels of the spinal cord [1881, 1882].

ADH abbreviation for antidiuretic hormone. see vasopressin.

adhesio interthalamica [N.A.] see massa intermedia; a small group of fibers that interconnect the thalamus along the midline; of no known functional significance.

adiadochokinesis cerebellar disorder characterized by the inability to perform rapidly alternate contractions of antagonistic muscles, as in finger tapping or alternate pronation and supination of the hands.

Adler, Alfred [1870–1937] Viennese psychiatrist who, with Jung and Freud, laid the foundations of modern psychology.

adrenergic releasing an epinephrine-like substance; pertaining to certain postganglionic-sympathetic nerve endings.

affenspalte see fissure, lunate.

afferent conducting toward.

afferent neuron sensory neuron [usually a ganglion cell] that conducts information toward the brain; contrasts with efferent neuron.

afterbrain see hindbrain.

after-nystagmus nystagmus in which the eye movements continue after the stimulus is removed.

agent, adrenergic blocking compound which selectively inhibits the responses of effector cells to adrenergic sympathetic nerve impulses and to epinephrine and related amines.

agnosia loss of ability to recognize familiar objects.

agnosia, auditory verbal inability to recognize spoken words.

agnosia, tactile inability to recognize objects by touch. Syn: astereognosis.

agnosia, visual object inability to recognize objects by sight.

agnosia, visual verbal inability to recognize written words. see also alexia.

agraphia inability to copy.

AICA an artery, the anterior inferior cerebellar, that nourishes the rostral part of the cerebellum.

akinesia absence of the initiation, implementation, and facility of execution of movement.

ala alba lateralis [L. ala—wing] see area, acoustic.

ala centralis most rostral subdivision of the cerebellar hemisphere, lateral to and continuous with the central lobule of the vermis. see cerebellum, lobules [hemispheres].

ala cinerea [L. cinereus—ashy] see trigone, vagal.

alar plate see plate, alar.

alba pertaining to the white matter of the brain.

alexia loss of ability to interpret written symbols; word blindness, therefore, inability to read. see also visual verbal agnosia.

allocortex unlaminated or partly laminated cortex of the archipallium and paleopallium. see also cortex, heterogenetic.

alveus [L. trough or canal] layer of myelinated fibers on the ventricular surface of the hippocampus arising from cells in the cornu ammonis and collecting to form the fimbria.

Alzheimer, Alois [1864–1915] German physician and neuropathologist who in 1907 described the pathologic changes in cortical neurons, characteristic of presenile sclerosis.

amaurosis [Gr. darkening] blindness.

amiculum olivae [L. amiculum—little overcoat] see capsule, olivary.

aminobutyric acid see gamma-aminobutyric acid.

Ammon Egyptian god, represented with ram’s horns, hence the term cornu ammonis, q.v.

Ammon’s formation see formation, hippocampal; hippocampus.

Ammon’s horn see cornu ammonis.

Ammon’s pyramids pyramidal cells of the cornu ammonis.

amphicyte satellite cell in the ectodermal capsule of ganglion cells.

ampulla, membranous [L. ampulla—jug] dilatation at one end of each semicircular duct [anterior inferior end of the superior duct, posterior inferior end of the posterior duct, and anterior end of the horizontal duct] and containing the crista ampullaris, the sensory end organ of the duct.

ampulla, osseous part of the bony labyrinth of the internal ear, which houses a membranous ampulla.

amyelia absence of the spinal cord.

amygdala [Gr. amygdale—almond] subdivision of the basal ganglia located in the temporal lobe, anterior to the inferior horn of the lateral ventricle and partly beneath the uncus. Its two main portions are a corticomedial nuclear group [anterior amygdaloid area, nucleus of the lateral olfactory tract, and the medial cortical and central amygdaloid nuclei] with olfactory and subcortical connections, and a basolateral nuclear group [basal, lateral, and accessory basal amygdaloid nuclei] connected primarily with the overlying cortex, [Crosby, Humphrey, and Lauer, 1962]. Syn: archistriatum.

analgesia insensitivity to pain without loss of consciousness.

Andersch, Carl Samuel [1732–1777] German anatomist [Göttingen] who described the inferior [petrosal] ganglion of the glossopharyngeal nerve [ganglion of Andersch].

anesthesia absence of sensation.

aneurysm, Berry saccular dilatation of a cerebral artery, usually located on or near the circle of Willis.

angiography procedure in which a contrast medium is injected into a vessel, such as an artery. to render the vessel and its branches visible by radiography.

angle, cerebellopontine area on the ventrolateral surface of the brain stem where the cerebellum, pons, and medulla meet and where the facial and acoustic nerves attach to the brain.

angle, filtration see angle, iris.

angle, iridial see angle, iris.

angle, iris recess at the junction of the iris and cornea where aqueous humor leaves the anterior chamber of the eye. Syn: filtration angle; iridial angle.

angle, Rolandic acute angle formed by the central sulcus and the superior border of the frontal lobe.

angle, venous point at the interventricular foramen where the terminal vein turns sharply posteriorly to enter the internal cerebral vein.

anhidrosis absence of sweating.

animal, decerebrate one in which the brain has been severed at the level of the midbrain.

animal, spinal one in which the spinal cord has been separated from the brain.

animal, thalamic one in which the cerebrum has been separated from the diencephalon.

aniscoria inequality in pupillary diameter of the two eyes.

ankle jerk see reflex, Achilles.

annulus see anulus.

anomia loss of ability to recall or to recognize the names of objects or people.

anosmia loss or lack of the sense of smell.

anosognosia inability of a person to recognize a disease or bodily defect in himself.

ansa cervica [L. ansa—handle] [N.A.] loop of the cervical plexus, formed by the union of the descendens hypoglossi, containing fibers from the C_l spinal nerve, and the descendens cervicalis, containing fibers from C₂ and C₃. Its branches supply the infrahyoid muscles. Syn: ansa hypoglossi.

ansa cruralis see ansa peduncularis.

ansa hypoglossi see ansa cervicalis.

ansa lenticularis [N.A.] 1. bundle of nerve fibers arising primarily from cells in the globus pallidus and putamen, emerging from the ventral surface of the lentiform nucleus, passing medially and dorsally into the diencephalon, then, after most fibers synapse in the nucleus of the field of Forel, ending in the midbrain tegmental gray including the caudal red nucleus. 2. several bundles of nerve fibers emerging from the lentiform nucleus and subdivided into three groups: a ventral division or ansa lenticularis proper [see 1 above], a dorsal division [the lenticular fasciculus], and an intermediate division [the subthalamic fasciculus].

ansa peduncularis [N.A.] fibers of the inferior thalamic peduncle and ansa lenticularis combined into one bundle which bends around the posterior limb of the internal capsule as it enters the midbrain. Syn: ansa cruralis, Reil’s ansa.

ansa sacralis loop of fibers interconnecting the caudal ends of the two sympathetic trunks.

ansa subclavia [N.A.] loop of nerve fibers around the subclavian artery connecting the inferior and middle cervical sympathetic ganglia or sometimes the inferior ganglion and the recurrent nerve.

ansa of Vieussens see ansa subclavia.

ansiform describing an arc.

anterior column see horn, ventral; funiculus, ventral.

anterior commissure see commissure, anterior.

anticholinesterase substance which blocks the action of cholinesterase.

antidiuretic hormone see vasopressin.

antidromic conducting impulses in the direction opposite to the usual direction of conduction.

antrum, interventricular, of Wilder portion of the third ventricle with which the two interventricular foramina communicate.

anulus of the aqueduct [L. annulus—ring] periaqueductal gray.

anulus of Vieussens see ansa subclavia.

aperture, lateral, of the fourth ventricle opening between each lateral recess of the fourth ventricle and the subarachnoid space. Syn: foramen of Luschka; foramen of Key and Retzius.

aperture, median, of the fourth ventricle midline opening in the posterior medullary velum through which the medullary portion of the fourth ventricle communicates with the subarachnoid space. Syn: foramen of Magendie.

aphasia language disorder involving a loss of ability to comprehend or express the signs and symbols by which man communicates with his peers.

aphasia, semantic loss of the ability to understand the importance and relationship of things in the external environment.

aphonia loss of voice; inability to phonate.

apparatus, Golgi see apparatus, reticular.

apparatus, reticular organoid found in nerve cell cytoplasm, most highly developed in large nerve cell bodies, and in some cases extending into the dendrites. Syn: Golgi apparatus.

apparatus, subneural modified sarcolemma of a motor end-plate.

apraxia inability to carry out a purposive movement, the nature of which the patient understands, in the absence of severe motor paralysis, sensory loss, and ataxia.

aqueduct, cerebral narrow channel through the midbrain, connecting the third and fourth ventricles. Syn: iter; aqueduct of Sylvius.

aqueduct, cochlear channel from the scala tympani to the surface of the petrous bone. Syn: cochlear canaliculus.

aqueduct of Sylvius see aqueduct, cerebral.

aqueduct of Cotunnius early term for the vestibular aqueduct.

aqueduct, vestibular narrow channel in the petrous part of the temporal bone, which contains the endolymphatic duct and sac.

arachnoid [Gr. arachne—spider] outer layer of the leptomeninges, which covers the brain and spinal cord smoothly without conforming to the irregularities of their surfaces.

arachnoid villi see villi, arachnoid.

arachnopia see leptomeninges.

Arantius [Aranzi], Giulio Cesare [1530–1589] Italian physician and anatomist who wrote extensively in various anatomical fields. He described the inferior horn of the lateral ventricle and named the hippocampus.

arbor vitae [L. tree of life] vermis of the cerebellum as seen in sagittal section.

Archambault’s loop temporal loop of the optic radiation.

archicerebellum [Gr. arch—beginning] flocculonodular lobe, the oldest portion of the cerebellum. see cerebellum, lobes.

archipallium see formation, hippocampal.

archistriatum see amygdala.

area see also cortex.

area acclinis area lateral to the medial longitudinal fasciculus in the dorsomedial region of the tegmentum throughout the brain stem. It contains large cells of the reticular formation and fibers which probably subserve a variety of functions.

area, acoustic area on the floor of the fourth ventricle overlying the vestibular and the dorsal cochlear nuclei. Syn: area acustica; ala alba lateralis.

area acustica see area, acoustic.

area adolfactif see area, parolfactory.

area, agranular frontal see area, motor.

area, anterior perforated see substance, anterior perforated.

area, Broca’s 1. posterior portion of the inferior frontal gyrus in the dominant hemisphere; Brodmann’s area 44 and adjoining part of area 45; motor aphasia is attributed to injury in this general region. 2. see area, parolfactory.

area[s], Brodmann’s numbered areas of the cerebral cortex subdivided by Brodmann on the basis of their cytoarchitectural characteristics. They include the following areas:

3, 1, and 2. the somesthetic area in the postcentral gyrus;

4. motor area in the precentral gyrus;

5. sensory association area in the superior parietal lobule posterior to the postcentral gyrus;

6. premotor area in the frontal lobe anterior to area 4;

7. sensory association area in the superior parietal lobule between areas 5 and 19;

8. frontal eye field in the frontal lobe anterior to area 6;

9. in the frontal lobe anterior to area 8;

10. in the anterior part of the frontal lobe including the frontal pole;

11. in the frontal lobe, ventral to areas 10 and 47 laterally and area 12 medially;

12. in the frontal lobe in the ventral part of the medial hemispheric wall;

17. striate area, visual projection cortex adjoining the calcarine fissure in the occipital lobe, including the occipital pole;

18. parastriate area, visual association cortex, adjacent to area 17 in the occipital lobe;

19. peristriate area [preoccipital cortex]. visual association cortex. adjacent to area 18 in the occipital lobe;

20. in the inferior temporal gyrus;

21. in the middle temporal gyrus, making up most of the gyrus;

22. auditory association cortex, mainly on the lateral surface of the superior temporal gyrus and adjoining areas 41 and 42;

23. in the posterior pan of the cingulate gyrus;

24. in the anterior part of the cingulate gyrus;

25. parolfactory area on the medial surface of the frontal lobe;

26. in the isthmus of the fornicate gyrus adjoining the corpus callosum;

27. in the parahippocampal gyrus, adjacent to the hippocampal fissure;

28. entorhinal area, making up most of the parahippocampal gyrus;

29. in the isthmus of the fornicate gyrus between areas 26 and 30;

30. in the isthmus of the fornicate gyrus just posterior to area 29;

31. in the cingulate gyrus just above area 23 and posterior to area 24;

33. in the cingulate gyrus adjacent to the anterior portion of the sulcus of the corpus callosum;

34. uncus of the temporal lobe;

35. adjacent to the rhinal fissure in the temporal lobe;

36. most of the fusiform gyrus in the temporal lobe;

37. in the posterior portion of the temporal lobe on its medial and lateral surfaces;

38. temporal pole;

39. angular gyrus;

40. supramarginal gyrus;

41 and 42. auditory projection area making up the transverse temporal gyri on the opercular surface of the temporal lobe;

44. opercular portion of the inferior frontal gyrus;

45. triangular portion of the inferior frontal gyrus;

46. part of the frontal eye field, in the middle frontal gyrus;

47. orbital portion of the inferior frontal gyrus.

48. retrosubicular area posterior to area 35 on the medial aspect of the temporal lobe;

52. on the opercular surface of the superior temporal gyrus between area 41 and the insula, probably an association area for auditory and perhaps visceral functions.

area, cuneiform see area, parolfactory.

area fasciculata see body, juxtarestiform.

area gigantopyramidalis portion of the precentral and paracentral gyri containing giant pyramidal [Betz] cells.

area, lateral olfactory collective term used for the temporal lobe nuclei in which olfactory tract fibers end, and comprising the prepyriform area, the lateral part of the anterior perforated substance, and the corticomedial portion of the amygdala.

area, medial hypothalamic that part of the hypothalamus medial to the anterior columns of the fornix.

area, medial olfactory collective term used to include the septum pellucidum, subcallosal gyrus, parolfactory area, olfactory trigone, and the medial part of the anterior perforated substance.

area of Monakow area in the medulla between the spinal nucleus and tract of V dorsolaterally and the inferior olivary nucleus ventromedially, and containing, among others, the lateral spinothalamic tract.

area, motor cortical area in the precentral gyrus containing giant pyramidal [Betz] cells in layer V and concerned with voluntary movement. Syn: Brodmann’s area 4: agranular frontal area.

area offactoria see substance, anterior perforated.

area, olfactory see substance, anterior perforated.

area, oval, of Flechsig lumbar portion of the septomarginal fasciculus.

area, paracommissural see area, parolfactory.

area, parastriate occipital lobe cortex adjacent to the visual or striate cortex. Syn: area 18 of Brodmann.

area, paraterminal narrow strip of cortex anterior to the lamina terminalis and separated from the parolfactory area by the posterior parolfactory sulcus. Sometimes this term is also used to include the parolfactory area and even the subcallosal gyrus as well. Syn: gyrus paraterminalis; paraterminal body.

area, parolfactory, of Broca area on the medial surface of the cerebral hemisphere, immediately anterior to the lamina terminalis and below the subcallosal gyrus. It consists of an anterior parolfactory gyrus between the anterior and posterior parolfactory sulci and a posterior parolfactory gyrus behind the posterior parolfactory sulcus. Syn: carrefour o1factif; cuneiform area; paracommissural area; precommissural septum; septal area; Brodmann’s area 25.

area, peristriate occipital lobe cortex anterior and adjacent to the parastriate area. Syn: Brodmann’s area 19; preoccipital cortex.

area, piriform see area, pyriform.

area postrema narrow ridge of glial and vascular tissue along the lateral edge of the caudal portion of the fourth ventricle.

area, precommissural septal see area, parolfactory.

area, prefrontal cortical area of the frontal lobe, anterior to the premotor area and including the frontal pole; the frontal association area.

area, premotor cortical area of the frontal lobe, anterior to the motor area, which upon stimulation produces gross movements. Syn: Brodmann’s area 6.

area, preoccipital see area, peristriate.

area, preoptic part of the telencephalon medium on each side of the third ventricle anterior to a plane extending from the interventricular foramen to the anterior surface of the optic chiasm. It is functionally related to the hypothalamus.

area, prepyriform clusters of nerve cells adjacent to the lateral olfactory stria on the ventral surface of the cerebrum. Syn: lateral olfactory gyri; prepyriform cortex.

area, pretectal midbrain area just rostral to the layers of the superior colliculus at the junction of the midbrain and diencephalon and containing, on each side, the pretectal nucleus, a midbrain center for the light reflex. Syn: pretectum.

area, pyriform cerebral cortex of the temporal lobe, including the lateral olfactory gyrus, uncus, and anterior part of the parahippocampal gyrus.

area, Rolandic the precentral and postcentral gyri of the cerebrum, adjacent to the central sulcus.

area, sensory association cortical area posterior to the postcentral gyrus and adjacent to the sensory projection cortex.

area, septal see area, parolfactory.

area, silent any cortical area which upon stimulation does not produce any detectable motor activity or sensory phenomenon, and in which a lesion may occur without producing detectable motor or sensory abnormalities.

area, somesthetic see cortex, somesthetic.

area striata see area, striate.

area, striate occipital lobe cortex adjoining the calcarine fissure and containing the macroscopic stripe of Gennari. Syn: Brodmann’s area 17; visual projection cortex; area striata.

area, strip narrow strip of cerebral cortex lying between Brodmann’s areas 4 and 6; a suppressor area which inhibits activity of area 4. Syn: Brodmann’s area 4s.

area, subcallosal region ventral to the genu of the corpus callosum and anterior to the lamina terminalis and consisting primarily of the subcallosal gyrus and parolfactory area.

area, supplementary motor any cortical area, other than Brodmann’s area 4, which on stimulation produces body or head movement.

area, suppressor any cortical area which upon stimulation inhibits the motor activity elicited from another cortical area.

area, vestibular door of the fourth ventricle lateral to the sulcus limitans, overlying the vestibular nuclei; a part of the acoustic area.

area, visual association Brodmann’s cortical areas 18 and 19, adjacent to the visual projection cortex.

area, Wernicke’s posterior third of the superior temporal gyrus. Syn: auditory association area.

areflexis absence of all reflexes.

Argyll Robertson, Douglas [1837–1909] Scottish ophthalmic surgeon who described the Argyll Robertson pupil [q.v.] in 1869.

Arnold-Chiari malformation developmental defect in which the cerebellum is elongated and extends through the foramen magnum into the spinal canal. The entire brain stem is stretched and displaced caudally and there is a hump on the posterior surface of the medulla. The upper cervical and lower cranial nerve roots slope upward to reach their foramina of exit. The apertures of the fourth ventricle are closed and the subarachnoid space at the level of the foramen magnum is sealed off, resulting in an obstructive hydrocephalus. Various theories have been advanced for the etiology of this condition. Most likely it does not result from caudal traction on the spinal cord secondary to a lumbosacral defect, as formerly supposed, but from overgrowth of the tissue in the region of the malformation or from an arrest in development of the hindbrain with failure of the pontine flexure to occur. [List, 1969].

Arnold, Friedrich [1803–1890] German anatomist who described the otic ganglion [Arnold’s ganglion] and the auricular branch of the vagus nerve [Arnold’s nerve] in 1828, the frontal corticopontine tract [Arnold’s tract] and the vagal trigone [Arnold’s area].

artery, accessory meningeal small branch of the internal maxillary artery which enters the cranial cavity through the foramen ovale and supplies the semilunar ganglion and neighboring dura.

artery, accessory middle cerebral anomalous branch of the anterior cerebral artery which, when present, accompanies the main trunk of the middle cerebral artery and shares part of its territory of distribution.

artery, accessory ophthalmic inconstant vessel arising from the anterior branch of the middle meningeal artery, which passes through the superior orbital fissure to supply structures in the orbit.

artery of Adamkiewicz great anterior radicular artery, which he called the “great anterior spinal artery.”

artery, anterior cerebral one of the two main branches of the internal carotid artery, it passes dorsally onto the medial surface of the frontal lobe and curves over the genu of the corpus callosum. Its cortical branches distribute to the medial aspect of the frontal and parietal lobes and some connect with the cortical branches of the middle cerebral artery laterally and the posterior cerebral artery posteriorly.

artery, anterior choroidal [choroidal] branch, usually of internal carotid artery, which passes posteriorly into the cerebrum and supplies, by way of small branches, various structures including the choroid plexus of the lateral ventricle, the lateral geniculate nucleus, and part of the region adjacent to the inferior horn of the lateral ventricle including the anterior portion of the hippocampus.

artery, anterior communicating short, usually single, midline vessel connecting the two anterior cerebral arteries and completing the circle of Willis anteriorly.

artery, anterior inferior cerebellar branch arising from the basilar artery near its origin from the two vertebral arteries. It supplies a part of the lateral portion of the medulla and of the pons and the anterior and inferior surfaces of the cerebellum. Syn: AICA, middle cerebellar artery.

artery, anterior median spinal see artery, anterior spinal.

artery, anterior meningeal branch of the anterior ethmoidal artery which supplies the dura mater of the anterior cranial fossa.

artery, anterior spinal unpaired midline artery extending along the ventral surface the full length of the medulla and spinal cord. It receives tributaries at its cranial end from the vertebral arteries and at spinal cord levels from radicular [medullary] branches. It supplies by way of its sulcal [central] branches most of the ventral two-thirds of the spinal cord and the paramedian portion of the medulla.

artery, anterolateral see artery, lateral striate.

artery, anteromedial see artery, medial striate.

artery, basilar large single midline artery on the ventral surface of the pons formed by the fusion of the two vertebral arteries, and supplying by way of its branches the pons, midbrain, and parts of the medulla, cerebellum, and forebrain.

artery, callosomarginal major branch which arises from the anterior cerebral artery usually anterior to the genu of the corpus callosum but sometimes near the origin of the anterior cerebral artery. It follows the cingulate [callosomarginal] sulcus, and usually gives rise to the internal frontal arteries and sometimes the paracentral artery.

artery, central 1. see artery, sulcal. 2. any one of the small branches of the circle of Willis, which enter the brain near their origin and supply structures near the midline. 3. branch of the ophthalmic artery which runs through the center of the optic nerve into the eyeball and divides into the retinal arteries.

artery of Charcot artery described by Charcot as the largest of the lenticulostriate arteries. It passes around the lateral border of the lenticular nucleus. Syn: artery of internal hemorrhage.

artery, frontopolar artery which usually arises from the anterior cerebral artery ventral to the genu of the corpus callosum but sometimes is a branch of the callosomarginal artery. It passes forward toward the frontal pole and supplies the anterior part of the superior frontal gyrus on the medial and lateral surfaces of the cerebrum and the anterior part of the middle frontal gyrus.

artery, ganglionic any of the small vessels which arise from the circle of Willis or from the proximal portions of its major branches, They enter and supply the deep structures within the forebrain.

artery, great anterior medullary large medullary artery which joins the anterior spinal artery, usually only on one side, at a lower thoracic or upper lumbar level. Syn: artery of Adamkiewicz.

artery, great posterior medullary large medullary artery [not so large as its anterior counterpart] which joins the posterior arterial plexus at a lower thoracic or upper lumbar level.

artery, great radicular great anterior or posterior medullary artery.

artery of Heubner see artery, recurrent.

artery, hippocampal any of several branches [1 to 4] of the posterior cerebral artery which course along the hippocampal fissure into which they send branches in a rake-like pattern. These vessels supply all but the most anterior part of the hippocampal formation, which is supplied by branches of the anterior choroidal artery.

artery, internal auditory branch usually arising from the anterior inferior cerebellar artery, occasionally from the basilar artery, and passing through the internal auditory meatus with the facial and acoustic nerves to supply structures within the petrous portion of the temporal bone. Syn: labyrinthine artery.

artery, internal carotid branch of the common carotid artery which passes through the carotid canal and cavernous sinus to enter the cranial cavity. It and its counterpart of the other side form part of the circle of Willis. Its main branches supply the frontal and parietal lobes, the lateral surface of the temporal lobe, certain basal forebrain structures, and the orbit.

artery of internal hemorrhage see artery of Charcot.

artery, labyrinthine see artery, internal auditory.

artery, lateral striate any one of a series of small arteries which arise from the proximal portion of the middle cerebral artery and which pass upward into the brain substance to supply the medial part of the head of the caudate nucleus, globus pallidus and putamen, the anterior and medial parts of the thalamus and most of the posterior limb of the internal capsule. Syn: anterolateral artery; lenticulostriate artery.

artery, lenticulostriate see artery, lateral striate.

artery, medial striate any of a group of small vessels which arise mainly from the proximal portions of the anterior and middle cerebral arteries. The anterior cerebral branches supply the anterior hypothalamus, septum pellucidum. medial part of the anterior commissure, anterior pillar of the fornix, and the anterior inferior part of the striatum. The middle cerebral branches penetrate the medial third of the anterior perforated substance and supply the outer segment of the globus pallidus. The recurrent artery, q.v., one of the larger medial striate arteries, supplies part of the caudate nucleus and putamen and part of the anterior limb of the internal capsule. Syn: anteromedial artery.

artery, medullary any one of the radicular arteries which communicate with the anterior spinal artery or the arterial plexus on the surface of the spinal cord.

artery, middle cerebellar see artery, anterior inferior cerebellar.

artery, middle cerebral large terminal branch of the internal carotid artery. It enters the lateral fissure of the cerebrum. Its cortical branches distribute to almost the entire lateral surface of the cerebrum and some anastomose with cortical branches of the anterior and posterior cerebral arteries on the medial surface of the cerebrum.

artery, middle meningeal branch of the internal maxillary artery which enters the cranial cavity through the foramen spinosum to supply much of the dura mater.

artery, ophthalmic branch arising from the internal carotid artery, usually just after it emerges from the cavernous sinus. It enters the orbit through the optic foramen and supplies various orbital structures. Because of its connections with the external carotid system, it sometimes serves as a channel for collateral circulation for the anterior and middle cerebral arteries. Its main branches include: the central artery of the retina and the lacrimal, supraorbital, ethmoidal, and palpebral arteries.

artery, orbital any of two or three branches which arise from the ascending portion of the anterior cerebral artery. They supply the orbital surface of the frontal lobe and the olfactory bulb and anastomose with the orbitofrontal branch of the middle cerebral artery.

artery, paracentral branch usually of the pericallosal but sometimes of the callosomarginal artery, which supplies the paracentral gyrus.

artery, penetrating any of the small vessels which arise from arteries on the surface of the brain and spinal cord, and which enter the substance of the central nervous system and end there in capillary networks.

artery, pericallosal terminal branch of the anterior cerebral artery which ties in the sulcus of the corpus callosum. It usually gives rise to the paracentral, precuneal, and posterior callosal branches and supplies the cingulate gyrus and the underlying corpus callosum.

artery, pontine any of the small branches which arise from the basilar artery and supply the pons.

artery, posterior callosal terminal branch of the pericallosal artery which supplies the underlying corpus callosum.

artery, posterior cerebellar see artery, posterior inferior cerebellar.

artery, posterior cerebral usually a large terminal branch of the basilar artery [sometimes it arises from the internal carotid artery]. It passes around the midbrain and its cortical branches supply the medial surfaces of the temporal and occipital lobes, some branches anastomosing with other cortical branches of the anterior and middle cerebral arteries.

artery, posterior choroidal [choroidal] branch of the posterior cerebral artery which supplies the choroid plexus of the third ventricle and sends a few branches also to part of the thalamus and the splenium of the corpus callosum.

artery, posterior communicating anastomotic vessel connecting the internal carotid and posterior cerebral arteries and forming a part of the circle of Willis.

artery, posterior inferior cerebellar branch of the vertebral artery which supplies the lateral portion of the medulla, inferior surface of the cerebellum and choroid plexus of the fourth ventricle. Syn: posterior cerebellar artery; PICA.

artery, posterior meningeal any of several small branches of the vertebral, occipital and other small arteries which supply the dura mater of the posterior fossa.

artery, posterior perforating see artery, thalamoperforating.

artery, posterior spinal one of two small branches of the vertebral arteries which descend, one on either side, along the dorsolateral surface of the medulla and upper spinal cord and become continuous with a posterior arterial plexus.

artery, posterolateral see artery, thalamogeniculate.

artery, posteromedial see artery, thalamoperforating.

artery, precuneal branch of the pericallosal artery which supplies the precuneus on the medial surface of the parietal lobe.

artery, premammillary any of several arteries which arise from the posterior communicating arteries [rarely from the anterior choroidal artery], penetrate the hypothalamus anterior to the mammillary bodies, and supply the tuber cinereurn and hypothalamus.

artery, radicular any one of the arteries which accompany and supply the spinal nerve roots and some of which, as medullary arteries, join the anterior spinal artery or the arterial plexus on the surface of the spinal cord.

artery, recurrent largest of the medial striate arteries, it arises from the anterior cerebral artery near its junction with the anterior communicating artery. Its branches penetrate the anterior perforated substance medial to the lateral striate arteries and supply mainly the anterior, inferior pan of the head of the caudate nucleus, putamen, and adjoining part of the anterior limb of the internal capsule. Syn: artery of Heubner.

artery, retromammillary see artery, thalamoperforating.

artery, sulcal any one of the branches of the anterior spinal artery which enter the ventral median fissure on the ventral surface of the medulla and spinal cord and supply capillary beds on one side or the other in the spinal cord or medulla. Syn: central artery.

artery, superior cerebellar branch of the basilar artery which arises bilaterally from the basilar artery just prior to the origin of the posterior cerebral arteries. It supplies the. upper part of the pons, the middle and superior cerebellar peduncles, part of the tectum, and the superior surface of the cerebellum.

artery, terminal caudal continuation of the anterior spinal artery along the filum terminale.

artery, thalamogeniculate any one of several small branches which arise from the posterior cerebral artery as it passes around the cerebral peduncle, and which supply the pulvinar, the medial part of the lateral geniculate nucleus, and of posterior thalamic structures. Syn: posterolateral artery.

artery, thalamoperforating any of the branches arising from the most proximate portion of the posterior cerebral artery near the bifurcation of the basilar artery. They enter the brain through the rostral part of the posterior perforated substance and fan out to supply the medial portions of the diencephalon and up to the midbrain. Syn: posterior perforating artery; posteromedial artery; retromammillary artery.

artery, thalamotuberal see artery, premammillary.

artery, vertebral a branch of the subclavian artery, it passes up, it passes upward through transverse foramina of the cervical vertebrae and enters the cranial cavity through the foramen magnum. It and its counterpart of the other side unite to form the basilar artery. Branches of the vertebrobasilar system supply the brain stem and cerebellum, the occipital and part of the temporal lobes, and certain basal forebrain structures.

association fibers see fibers, association, of the cerebrum.

astasia cerebellar disorder characterized by irregular, jerky muscle contractions during voluntary movement.

astereognosis see agnosia, tactile.

astrocyte neuroglial cell associated with the blood vessels of the central nervous system. Syn: astroglia; spider cell.

astrocyte, fibrous astrocyte of the type located primarily in the white matter of central nervous system.

astrocyte, protoplasmic astrocyte of the type located primarily in the gray matter of the central nervous system.

astroglia see astrocyte.

ataxia disorder of movement characterized by incoordination.

ataxia, Friedreich’s hereditary spinal ataxia with loss of a sense of position described by Friedreich in 1875.

athetosis disorder in which there are slow, twisting, involuntary movements of the extremities, particularly of the fingers and hands.

atrium of the lateral ventricle part of the lateral ventricle which connects the posterior portion of the body of the ventricle with the inferior horn, and with the posterior horn. Syn: collateral trigone or triangle; vestibule.

atrophy, Gudden’s retrograde degeneration of the thalamus, after destruction of certain cortical areas.

atrophy, progressive muscular amyotrophic lateral sclerosis.

atropine agent used to block parasympathetic discharge; an alkaloid drug capable among other things, of blocking muscarinic cholinergic nerve endings.

auditory nerve see nerve, acoustic.

Auerbach, Leopold [1828–1897] German anatomist who described the myenteric plexus [Auerbach’s plexus] in 1862.

aula midline portion of the prosencephalic ventricle.

autonomic nervous system see system, autonomic nervous.

avalanche conduction see conduction, avalanche.

axilemma see axolemma.

axillary nerve see nerve, axillary.

axis, anatomical, of the eye see axis, optical.

axis, cerebrospinal see system, central nervous.

axis cylinder see neuraxis, 1.

axis, optical imaginary fine through the eye between the center of the corneal curvature anteriorly and the center of the posterior curvature of the eyeball. Syn: anatomical axis of the eye.

axis, visual imaginary line through the eye passing through the center of the lens and the center of the fovea centralis.

axolemma [axilemma] cell membrane of a neuraxis. Syn: Mauthner’s sheath.

axon [axone] that process of a neuron which conducts impulses away from the cell body.

axon hillock area in the nerve cell body devoid of Nissl granules, located at the point of origin of the axon.

axon reflex see reflex, axon.

axoplasm cytoplasm of the neuraxis of a nerve cell.

b

B-fiber myelinated nerve fiber having a diameter of 3 µm or less.

Babinski, Josef [1857–1932] French neurologist, who described the Babinski reflex [q.v.] in 1896.

bag, nuclear aggregation of spherical, centrally placed nuclei in the mid-portion of an intrafusal muscle fiber.

Baillarger, Jules Gabriel François [1806–1891] French neurologist who described two white lines or bands of nerve fibers in layers IV and V of the cerebral cortex [stria Baillarger, q.v.] in 1840.

band of Büngner see fiber, band.

band, diagonal, of Broca band of fibers that extends from the parolfactory area of the medial surface of the frontal lobe ventrally and along the lateral margin of the optic tract and marking the caudal boundary of the anterior perforated substance. Syn: olfactory radiation of Zuckerkandl.

band fiber see fiber, band.

band, Giacomini’s anterior part of the dentate gyrus next to the inferior surface of the uncus.

Bandfasern see fiber, band.

Bárány, Robert [1876–1936] Viennese otologist noted for his work on the physiology and pathology of the vestibular apparatus. see sign, Bárány’s.

barrier, blood-brain the barrier by which many substances, easily permeable through vessel walls in other parts of the body, are prevented from passing through blood vessel walls into central nervous system tissue.

basal ganglia see ganglia, basal.

basal nuclei of Meynert see substantia innominata [of Reichert].

basal plate see plate, basal.

basilar membrane see membrane, basilar.

basis pedunculi ventral portion of the cerebral peduncle of the midbrain composed of a fibrous portion [pes pedunculi] containing pyramidal and corticopontine tracts, and a cellular portion [substantia nigra].

basis pontis ventral portion of the pons, composed of descending pyramidal and corticopontine tracts, transverse pontocerebellar fibers, and pontine gray.

Bauhin, Caspar [1560–1624] Swiss botanist and anatomist who named the phrenic nerve.

Bechterew, Vladimir Michailovich [1857-1927] Russian neurologist who described the superior vestibular nucleus [Bechterew’s nucleus] in 1908. Bechterew’s bundle is the spinoolivary tract.

Bell, Sir Charles [1774–1842] Scottish neurologist and anatomist. In 1811 he described experiments which demonstrated the motor function of the ventral roots. In 1830 he described the long thoracic nerve [Bell’s nerve], the motor branch of the facial nerve and facial palsy [Bell’s palsy]. see law, Bell-Magendie.

Berengarius [Jacob Berenger] of Carpi [1480–1550] Italian anatomist and surgeon, who described, among other things, the corpus striatum, pituitary gland, and fourth ventricle of the brain.

Berger, Hans [1873–1941] German neurologist who was the first to record the electrical activity of the human brain. One of the basic electroencephalographic patterns bears his name.

Bergmann layer see layer, Bergmann.

Betz, Vladimir [1834–1894] Russian anatomist who described the giant pyramidal cells of the cerebral cortex [Betz cells] in 1874.

Bichat, Marie François Xavier [1771–1802] French anatomist and physician who described, among other things, the arachnoid membrane in 1800.

biventer one subdivision of the paramedian lobule of the posterior lobe of the cerebellar hemisphere. see cerebellum, lobules [hemispheres].

bladder, atonic bladder which lacks a sensory nerve supply, after degeneration of the sacral dorsal roots or dorsal root ganglia, as in tabes dorsalis. The bladder is greatly distended with overflow incontinence.

bladder, automatic see bladder, reflex.

bladder, autonomous bladder which lacks any nervous control, after injury to the sacral spinal cord, cauda equina, or pelvic plexus or nerves. The bladder is distended, empties irregularly and incompletely with much residual urine.

bladder, neurogenic bladder characterized by some disordered function, resulting from a lesion of the nerves supplying the bladder or of the central nervous system.

bladder, reflex bladder controlled by reflex function only, after injury to tracts between the sacral spinal cord and higher centers or to parts of the brain concerned with bladder function. Bladder capacity is reduced; micturition is sudden and uncontrolled and there is no residual urine. Syn: automatic bladder.

bladder, uninhibited one which is controlled only by reflex action, as in normal infants or in adults with some brain damage or deficiency. Bladder capacity may be slightly decreased. Micturition occurs suddenly and without control. There is no residual urine.

blood-brain barrier see barrier, blood-brain.

Bochdalek, V. A. [1801–1883] anatomist in Prague. The lateral recesses of the fourth ventricle and its choroid plexus, which extends through the lateral aperture, constitute the flower basket of Bochdalek [Bochdaleksches Blümenkörbchen].

body see also corpus; nucleus; granule.

body, Barr see nucleolus, satellite.

body, carotid small collection of cells at the bifurcation of each common carotid artery. It serves as a chemoreceptor and functions in respiratory reflexes.

body, cell enlarged portion of the neuron, containing the nucleus of the cell and surrounding cytoplasm [perikaryon] with its Nissl granules and other organelles and excluding all the cell processes. Syn: nerve cell; cyton; soma. see also of origin.

body[-ies], chromaffin chromaffin tissue similar to the chromaffin cells of the adrenal gland, but located mainly along the abdominal aorta. Syn: paraganglion; Zuckerkandl’s bodies.

body, ciliary structure which circles the iris, whose muscle contracts in accommodation and whose epithelium secretes aqueous humor.

body of the corpus callosum large mid-portion of the corpus callosum between the genu and the splenium. Syn: truncus corporis callosi.

body, external geniculate see body, lateral geniculate.

body, inferior quadrigeminal see colliculus, inferior.

body, internal geniculate see body, medial geniculate.

body, juxtarestiform inner portion of the inferior cerebellar peduncle, composed primarily of vestibulocerebellar and cerebellovestibular fibers. Syn: fasciculata.

body, lateral geniculate mass composed of the lateral geniculate nucleus, located lateral to the medial geniculate body, and serving as the thalamic center for the visual system.

body of Luys see nucleus, subthalamic.

body, mammillary protuberance on the ventral surface of the hypothalamus containing the mammillary nucleus. Syn: corpus albicans; corpus mammillare.

body, medial geniculate protuberance on the lateral surface of the rostral part of midbrain, overlying the medial geniculate nucleus and serving as the thalamic center for the auditory system.

body, Pacchionian enlarged arachnoid granulation.

body, paraterminal see area. paraterminal.

body, pineal subdivision of the epithalamus, located in the midline, just posterior to the dorsal portion of the third ventricle and rostral to the superior colliculus. Syn: conarium; epiphysis cerebri; pineal gland.

body, quadrigeminal any one of the four colliculi of the tectum.

body, restiform see peduncle, inferior cerebellar.

body, superior quadrigeminal see colliculus, superior.

body, tigroid see granules, Nissl.

body, trapezoid nerve fibers and cell bodies in the ventral and caudal part of the pontine tegmentum, which are a part of the auditory pathway between the cochlear nuclei and the medial geniculate and inferior collicular nuclei. Syn: corpus trapezoideum.

body, vitreous transparent, sernisolid gelatinous structure which fills the vitreous chamber of the eye behind the lens. Syn: vitreous humor.

body[-ies], Zuckerkandl’s chromaffin bodies [q.v.] along the abdominal aorta.

Boettcher, Arthur [1831–1889] German anatomist who described many anatomical features of the internal ear including a small ganglion on the vestibular nerve [Boettcher’s ganglion]. Boettcher’s cells are small polyhedral cells interposed between the basilar membrane and the cells of Claudius of the external spiral sulcus in parts of the basal coil of the cochlea.

bouton[s] termina1[-aux] see neuropodium.

Bowman, Sir William [1816–1892] English surgeon noted for his studies of the anatomy and physiology of the eye and of the kidney. For Bowman’s membrane. muscle, see the nouns.

brachium [L. arm] large bundle or trunk of nerve fibers in the central nervous system, consisting of one or more tracts. see also peduncle.

brachium conjunctivum see peduncle, superior cerebellar.

brachium conjunctivum descendens fibers of the superior cerebellar peduncle. probably arising from the dentate and emboliform nuclei, which, after crossing the midline, leave the peduncle, descend, and end mostly in the inferior olivary and accessory olivary nuclei.

brachium of the inferior colliculus fiber bundle running from the inferior colliculus to the medial geniculate nucleus. Syn: peduncle of the inferior colliculus.

brachium of the medial geniculate nucleus see brachium of the brachium pontis see peduncle, middle cerebellar.

brachium of the superior colliculus layer of fibers which pass over the surface of the medial geniculate body to enter the superior colliculus. They are internal corticotectal tract fibers which arise from the occipital and preoccipital cortices.

brain that portion of the central nervous system contained within the cranium.

brain, end see cerebrum; telencephalon.

brain sand calcareous bodies in the pineal body. Syn: acervuli.

brain, split one in which the corpus callosum and sometimes other forebrain commissures have been severed by a midline incision.

brain stem [brainstem] see stem, brain.

branchial efferent . pertaining to the special visceral efferent component of nerves conducting impulses from motor nuclei to striated muscle of branchiomeric [visceral arch] origin.

Breschet, G. [1784‑18451 anatomist in Paris. Breschet's veins are the diploic veins.

Broca, Peter Paul [1824‑18801 French surgeon and anthropologist who described aphasia as a manifestation of injury to the left inferior frontal gyrus, and introduced the concept of cerebral localization in 1861. see area, Broca's; band, diagonal, of Broca.

Brodmann, Korbinian [1868‑1918] German neurologist noted for his studies of the cytoarchitecture of the mammalian cerebral cortex, especially for his maps of the human cortex published in 1909, 1911. see areas, Brodmann's.

Brown‑Séquard, Charles Edouard 1817‑1894 British physiologist and neurologist. His description of the disorder resulting from hemisection of the spinal cord [Brown‑Séquard syndrome] was published in 1850.

Brown, vein of vein of the septum pellucidum.

Bruch, K. W. L. [1819‑1885] anatomist in Basel. Bruch’s membrane is the glassy membrane of the choroid of the eye.

Brücke, E. W. R. [1819‑1892] Viennese physiologist. Brücke's muscle consists of the meridional fibers of the ciliary muscle.

Burdach, Karl Friedrich [1776-1847] German anatomist and physiologist who first described nucleus and fasciculus cuneatus [nucleus and tract of Burdach] in detail

bulb see medulla oblongata.

bulb, cerebral see medulla oblongata.

bulb, end, of Krause small, encapsulated nerve ending, thought to be a cold receptor. jugular vein just below the

bulb, jugular bulbous enlargement of the internal jugular foramen. Syn: jugular sinus.

bulb, olfactory enlargement on the orbital surface of the cerebrum in which the olfactory nerve fibers terminate.

bulbar pertaining to the brain stem.

bundle see also column; fasciculus; tract.

bundle, Bechterew's see tract, spinoolivary, see tract, central tegmental.

bundle, comb see tract. nigrostriate.

bundle, comma see fasciculus interfascicularis.

bundle, ground see fasciculus proprius.

bundle, Held’s see tract, medial tectospinal.

bundle, hook see fasciculus, uncinate, 1.

bundle, Krause's see fasciculus solitarius.

bundle, medial forebrain fiber bundle interconnecting the anterior perforated substance and olfactory centers of the medial hemisphere with the preoptic and hypothalamic areas.

bundle, medial longitudinal see fasciculus, medial longitudinal.

bundle, olivocochlear bundle of nerve fibers originally presumed to arise from cells in the superior olive. They cross the midline. leave the brain stem with the vestibular nerve. then join the cochlear nerve to end in the organ of Corti.

bundle, oval lumbar portion of the septomarginal fasciculus.

bundle, Pick's corticobulbar fibers which accompany the corticospinal tract fibers through the pyramidal decussation then ascend to end in nucleus ambiguus.

bundle, posterior longitudinal see fasciculus, medial longitudinal.

bundle, predorsal, of Edinger see tract. medial tectospinal.

bundle of Probst bundle of nerve fibers along the medial wad of the cerebrum in brains lacking a corpus callosum. It is probably composed of fornix fibers and association fibers.

bundle, reflex see fasciculus proprius.

bundle, respiratory [Gierke's] see fasciculus solitarius.

Büngner, band of see fiber, band.

Burdach, Karl Friedrich [1776‑1847] German anatomist and physiologist who described nucleus and fasciculus cuneatus [nucleus and tract of Burdach].

c

C‑fiber small. unmyelinated nerve fiber. Syn: fiber of Remak.

Cajal see Ram6n y C4jal.

Cajal, Interstitial nucleus of the interstitial nucleus of the medial longitudinal fasciculus.

calamus scriptorius floor of the tapered caudal portion of the fourth ventricle.

calcar avis eminence of the medial wall of the posterior horn of the lateral ventricle, overlying part of the calcarine fissure. Syn: hippocampus minor.

callosal pertaining to the corpus callosum.

calyx[‑ces] of Held pericellular nerve endings in the trapezoid gray.

canal, carotid channel in the base of the skull through which the internal carotid artery and its accompanying carotid plexus pass to enter the cavernous sinus.

canal, central narrow channel extending throughout the spinal cord and the closed portion of the medulla. Syn: syringocele.

canal of Cloquet hyaloid canal of the developing eye.

canal, cochlear spiral tube of the bony labyrinth which winds around the modiolus. It is subdivided into the scala vestibuli and scala tympani and partially encloses the cochlear duct.

canal, hypoglossal opening in the occipital bone just above each occipital condyle, through which the hypoglossal nerve passes.

canal, neural see neurocele.

canal, optic see foramen, optic.

canal, sacral caudal continuation of the spinal canal into the sacrum.

canal of Schlemm canal which encircles the cornea at the corneoscleral junction. It drains aqueous humor from the spaces of Fontana and communicates with the venous system by way of the aqueous veins. Syn: sinus venosus sclerae.

canal, spinal see canal, vertebral.

canal, spiral irregularly shaped cavity in the modiolus, which contains the spiral ganglion.

canal, vertebral channel extending throughout the spinal column, and enclosing the spinal cord and its meninges. Syn: spinal canal.

canaliculus, cochlear see aqueduct, cochlear.

cap of Broca see gyrus, triangular.

capsule, external layer of nerve fibers between the putamen and the claustrum.

capsule, extreme layer of nerve fibers between the claustrum and the insular cortex.

capsule of the inferior colliculus fibers from the lateral lemniscus which surround and end in the nucleus of the inferior colliculus.

capsule, internal mass of nerve fibers between the caudate and thalamic nuclei medially and the lentiform nucleus laterally and connecting the cerebral cortex with various subcortical centers.

capsule, internal, anterior limb that part of the internal capsule between the head of the caudate nucleus medially and the lentiform nucleus laterally. It comprises the frontal corticopontine tract and the anterior thalamic radiations, capsule, internal, genu that part of the internal capsule between the posterior part of the head of the caudate nucleus and anterior part of the thalamus medially and the lentiform nucleus laterally. It comprises the corticobulbar fibers of the pyramidal tract and the thalamocortical fibers which end in areas 4 and 8.

capsule, internal, posterior limb those portions of the internal capsule between the thalamus and body of the caudate nucleus medially and the lentiform nucleus laterally [thalamolenticular portion], posterior to the lentiform nucleus [postlenticular portion], and inferior to the lenticular nucleus [sublenticular portion]. The thalamolenticular portion consists primarily of the corticospinal tract and the sensory radiations [including thalamocortical fibers to frontal and parietal lobes], also corticorubral and corticotegmental fibers. The postlenticular portion consists of visual and posterior thalamic radiations and the occipitotemporoparietal corticopontine tracts. The sublenticular portion contains auditory radiations and the temporal loop of the visual radiations.

capsule, olivary terminal portions of the fibers of the central tegmental tract as they enclose and enter the inferior olivary nucleus. Syn: amiculum olivae.

capsule, otic layer of hard bone within the petrous part of the temporal bone, which encloses the bony labyrinth.

capsule, Tenon’s fascia bulbi of the eye,

carotid siphon see siphon, carotid.

carrefour olfactif see area, parolfactory.

cataplexy disorder characterized by the sudden relaxation of all muscles, particularly those of the lower extremities, in response to an emotional stimulus.

cauda equina [L. cauda—tail; equus—horse] [B.N.A.] lumbosacral nerve roots as they descend through the subarachnoid space from the spinal cord to emerge through their respective intervertebral or sacral foramina.

caudate having a tail, see nucleus, caudate.

cave, Meckel's see cavum trigeminale.

cavity, tympanic middle ear.

cavity, neural the spinal canal and cranial cavity.

cavern Monro telencephalic portion of the third ventricle.

cavum septum pellucidum closed space within the septum pellucidum and which neither contains cerebrospinal fluid nor communicates with the ventricular system. Syn: fifth ventricle.

cavum trigeminale [N.A.] invagination of the dura mater of the lateral wall of the cavernous sinus, containing the root, semilunar ganglion, and proximal portions of the divisions of the trigeminal nerve. Syn: Meckel's cave, space or cavity.

cavum Vergae posterior extension of the cavity of the septum pellucidum.

cecum, cupular blind pouch at the apical end of the cochlear duct. Syn: lagena.

cecum, vestibular blind pouch at the basal end of the cochlear duct, near the junction of the cochlear duct and ductus reuniens.

cell[s], basket inhibitory cell located in the deep portion of the molecular layer of the cerebellar cortex, with basket-like axonal terminations around the cell bodies of Purkinje cells.

cell, Betz giant pyramidal cell in layer V of the motor cortex in the precentral gyrus.

cell body see body, cell.

cell[s], border cells which line the internal spiral sulcus of the cochlear duct.

cell, compound granular see cell, gitter.

cell[s], ependymal ciliated, nonsecretory cells which line the ventricular spaces of the central nervous system.

cell[s] of Fañanas elongated neuroglial cells, peculiar to the molecular layer of the cerebellum. These cells are characterized by numerous stubby processes which maintain dose relations with the processes and body of Purkinje cells. Syn: feather cells.

cell[s], feather see cell[s] of Fañanas.

cell, ganglion 1. nerve cell body in a sensory or autonomic ganglion of the peripheral nervous system. 2. old term for any nerve cell body either inside or outside the central nervous system.

cell, gitter round cell with granular cytoplasm and eccentric nucleus found in areas of degeneration in the central nervous system; presumably a phagocytic cell derived from microglia.

cell, Golgi [cerebellum] neuron whose cell body is located in the granular layer of the cerebellar cortex. The dendrites of these cells branch profusely in the molecular layer. The axons branch in the underlying granular layer immediately beneath the spread of the dendrites. These cells are said to be inhibitory over the granule cells.

cell, Golgi, type I neuron having a large cell body and a long axon.

cell, Golgi, type II neuron having a small cell body and a short axon. Internuncial neurons present throughout the central nervous system, stellate cells of the cerebral and cerebellar cortices, granule cells of the cerebellum are examples of this kind of cell.

cell group see nucleus.

cell[s], granule nerve cells having a diameter of 5 to 8 µm, in the granular layer of the cerebellar cortex. Their dendrites synapse with mossy fibers. Their axons enter the molecular layer and branch as parallel fibers.

cells of Hensen tall supporting cells between the outer hair and phalangeal cells of the organ of Corti on one side and the cuboidal epithelium of the cells of Claudius on the other.

cell[s], horizontal, of Cajal [cerebral cortex] neurons with small, fusiform cell bodies and long processes within the molecular layer [layer I] of the cerebral cortex.

cell, Hortega see microglia.

cell[s], intermediate, of Lugaro fusiform, horizontal cell, present in the granular layer of the cerebellar cortex.

cell[s], Kiss multipolar cells in the dorsal root ganglia which are presumably autonomic, postganglionic cell bodies and thought by some observers to be a part of the spinal parasympathetic system for vasodilatation.

cell[s], lower stellate [cerebellum] see cell[s], basket.

cell[s], marginal cells of the posterior marginal nucleus arranged tangentially on the apical surface of the dorsal horn of the spinal cord.

cell[s] of Martinotti [cerebral cortex] neurons whose cell bodies are intermingled with the pyramidal cells. Their axons, directed toward the surface of the cerebral cortex, give off collaterals to the layers through which they pass, then spread out horizontally in the molecular layer [layer 11 and terminate.

cell, mitral one of the large mitre‑shaped cells of the olfactory bulb with which the olfactory nerve fibers synapse and which send their axons into the olfactory tract.

cell, nerve 1. see neuron. 2. see body, cell.

cell, neuroglial see neuroglia. nuclei of

cell[s], neurosecretory nerve cells of the supraoptic and paraventricular n the hypothalamus which produce vasopressin and oxytocin, respectively, two neurohypophysial hormones, and transport them to the neurohypophysis, where they are released.

cell[s], obscure small, darkly staining, unipolar, sensory ganglion cells whose processes are unmyelinated or thinly myelinated and which conduct impulses for pain from the periphery and impulses from the viscera.

cell, Opalski large oval‑to‑round cell [up to 35 µm in diameter] without processes; with small, darkly staining, oval nucleus usually centrally placed; located primarily in the thalamus, globus pallidus, substantia nigra, and subthalamic nucleus but not in the striatum, in cases of hepatolenticular degeneration.

cell of origin cell body of a neuron, the axon of which contributes to some nerve fiber bundle.

cells, outer phalangeal supporting cells between and adjacent to the outer hair cells of the organ of Corti. Syn: cells of Deiters.

cell, Purkinje large cell of the cerebellar cortex, whose dendrites ramify in a single plane in the molecular layer, and whose axons terminate mostly in the cerebellar nuclei.

cell[s], relay [retina] bipolar cells.

cell[s], Renshaw small neurons in the ventral horn of the spinal cord, which presumably receive their afferent stimulation from axonal collaterals of neighboring motor neurons and which, in turn, probably synapse with the same motor neurons.

cell, rod see microglia.

cell[s], satellite cells which compose the ectodermal capsule of a ganglion cell and are continuous with the neurolemma.

cell[s], Schwann cells which constitute the neurolemma.

cell, spider see astrocyte.

cell, stellate 1. any small neuron having a star‑shaped cell body. Such cells serve as internuncial neurons in various parts of the central nervous system, including cortex. 2. inhibitory cell in the outer portion of the molecular layer of the cerebellar cortex. Its axons synapse with the dendrites of Purkinje cells. Basket cells in the deep portion of this layer are sometimes called 'lower stellate cells’.

central subdivision of the cerebellar vermis between the lingula and culmen. see cerebellum, lobules [vermis].

central nervous system see system, central nervous.

centrencephalic pertaining to the central core of brain tissue extending through the brain stem to the diencephalon. see system, centrencephalic.

centrifugal away from the central nervous system.

centripetal toward the central nervous system.

centrum ovale see centrum semiovale. Centrum semiovale mass of white matter within the cerebrum, between the cerebral cortex and the basal ganglia, at the level of the body of the corpus callosum. Syn. centrum ovale.

cephalic toward the head.

cephalic pertaining to the head.

cephalocele hernia of the brain.

cerebellar pertaining to the cerebellum.

cerebellopontine angle see angle, cerebellopontine.

cerebellum subdivision of the brain, derived from the alar plates of the metencephalon. It consists of a median portion, the vermis, and two lateral portions, the cerebellar hemispheres. It is concerned with coordination and with the regulation of muscle tone. see also cortex, cerebellar.

cerebellum, lobes the cerebellum is subdivided differently by different authors. The terms used by Larsell, Ingvar, and Elliot Smith for the lobes of the cerebellum and their constituent parts are given here as summarized by Crosby, Humphrey, and Lauer [1962].

lobe, anterior [Larsell, Ingvar, and Elliot Smith] subdivision of the cerebellum anterior to the preclival fissure, comprising the lingula, central, and culmen of the vermis and the ala centralis and anterior crescentic lobules of the hemispheres.

lobe, flocculonodular [Larsell the most caudal subdivision of the cerebellum, comprising the nodule of the vermis and the flocculi of the hemispheres and the peduncles of the flocculi connecting them; the archicerebellum.

lobe, middle 1. subdivision of the cerebellum bounded rostrally by the preclival fissure and caudally by the postpyramidal fissure of the vermis and the posterolateral fissure of the hemispheres, and comprising a lobulus simplex. a

lobulus medius medianus, and a lobulus ansoparamedianus [Ingvar. 2, subdivision of the cerebellum bounded rostrally by the preclival fissure and caudally by the prepyrarnidal fissure of the vermis and the posterolateral fissure of the hemispheres, and comprising a lobulus simplex, a lobulus medius medianus [different from that of Ingvar], and a lobulus ansoparamedianus [Elliot Smith].

lobe, posterior 1. subdivision of the cerebellum bounded rostrally by the preclival fissure and caudally by the postnodular fissure of the vermis and posterolateral fissure of the hemispheres, and comprising a lobulus simplex, a lobulus medianus, and a hemispheric part between lobulus simplex and the flocculus [Larsell]. 2. caudal subdivision of the cerebellum comprising the pyramis, cerebellum, lobules uvula, and nodule of the vermis and the flocculi of the hemispheres [Ingvar. 3. caudal subdivision of the cerebellum, comprising the uvula and nodule of the vermis and the flocculi of the hemispheres [Elliot Smith].

cerebellum, lobules the subdivisions of the posterior lobe of Larsell and the middle lobes of Ingvar and of Elliot Smith are as follows:

lobule, ansiform 1. posterior superior and posterior inferior lobules [Crus and Crus III of the cerebellar hemisphere, above and below the great horizontal fissure [Larsell]. 2. same as I., but also including the biventer of the hemisphere [Ingvar, Elliot Smith].

lobule, ansoparamedian combined ansiform and paramedian lobules, an comprising: 1. posterior superior, posterior inferior and gracile lobules of the cerebellar hemisphere [Larsell]; or 2. same as I., but also including the biventer and tonsil Ingvar, Elliot Smith].

lobulus medianus [Larsell] subdivision of the vermis caudal to lobulus simplex, and comprising folium vermis, tuber, pyramis, and uvula.

lobulus medius medianus subdivision of the vermis caudal to lobulus simplex and comprising: 1. folium vermis and tuber [Ingvar or 2. same as 1., but also including pyramis [Elliot Smith].

lobule, paramedian subdivision of the cerebellar hemisphere corresponding to: 1. gracile lobule [Larsell]; or 2. tonsil [Ingvar, Elliot Smith]. Syn: lobulus: paramedianus.

lobulus simplex most rostral subdivision of the posterior lobe of Larsell: middle lobe of Ingvar and Elliot Smith, located between the preclival an[ postclival fissures on the superior surface of the cerebellum, and consisting of the posterior crescentic lobule of the cerebellar hemisphere and the clivus of the vermis. Syn: simple lobule.

cerebellum, lobules [hemispheres] the subdivisions of the cerebellar hemisphere, in rostral to caudal order, are as follows:

ala centralis [L. ala—wing] most rostral segment of the cerebellar hemisphere, continuous with the central lobule of the vermis and anterior to the postcentral fissure, in the anterior lobe on the superior surface of the cerebellum.

lobule, anterior crescentic segment of the anterior lobe on the superior surface of the cerebellar hemisphere, continuous with the culmen of the vermis. It is located between the postcentral fissure and ala centralis anteriorly and the preclival fissure and posterior crescentic lobule posteriorly, Syn: anterior semilunar lobule; anterior quadrangular lobule.

lobule, posterior crescentic hemispheric portion of lobulus simplex, on the upper surface of the cerebellum, continuous with the clivus of the vermis. It is separated from the anterior crescentic lobule by the preclival fissure and from the posterior superior lobule by the postclival fissure. Syn: posterior semilunar lobule; posterior quadrangular lobule.

lobule, posterior superior segment on the superior surface of the cerebellar hemisphere, continuous with folium vermis, and located between the postclival fissure anteriorly and the great horizontal fissure posteriorly. Syn: superior semilunar lobule. Crus I of Larsell.

lobule, posterior inferior segment mostly on the posterior inferior surface of the cerebellum, lobules [vermis] the cerebellar hemisphere, continuous with the tuber of the vermis. and located between the great horizontal fissure above it and the postpyramidal fissure anterior to it. Syn: inferior semilunar lobule; Crus I of Larsell.

lobule, gracile slender segment of cerebellar hemispheres between the biventer and the posterior inferior lobule, or it is a part of the posterior inferior lobule. Syn: paramedian lobule of Larsell.

biventer segment consisting of two portions on the inferior surface of the cerebellar hemisphere, continuous with the pyramis of the vermis. The postpyramidal fissure separates it posteriorly and laterally from the posterior inferior lobule. The prepyramidal fissure separates it medially from the tonsil. The flocculus adjoins it anteriorly. Syn: biventral lobule.

tonsil an ovoid mass continuous with the uvula of the vermis, that lies between the vermis and the biventer on the inferior surface of the cerebellar hemisphere. Because of its position close to the midline and dorsal to the medulla, it can, under certain adverse conditions, herniate through the foramen magnum, acting as a pressure cone against the medulla.

flocculus most caudal subdivision of the cerebellar hemisphere. It is a small projection on the anterior surface of the cerebellum, just lateral to the attachment of the acoustic nerve at the pontomedullary junction.

cerebellum, lobules [vermis] the subdivisions of the cerebellar vermis, in rostral to caudal order, are as follows:

lingula most rostral segment of the vermis located in the anterior medullary velum. and sometimes also including the adjacent segment of the vermis. It is not continuous with the biventer of the cerebellar hemispheres.

central segment consisting of one or two portions on the anterior, superior surface of the vermis. It is separated from the lingula by the precentral fissure and from the culmen by the postcentral fissure. It is continuous with the ala centralis of the cerebellar hemisphere.

culmen [N.A.] segment on the superior surface of the vermis, separated from the central lobule by the postcentral fissure anteriorly and from the clivus by the preclival fissure posteriorly. It is continuous with the anterior crescentic lobule of the hemisphere. Syn: culmen monticuli.

clivus. [L. slope of a hill] segment on the superior surface of the vermis, separated from the culmen by the preclival fissure anteriorly and from folium vermis by the postclival fissure posteriorly. It is continuous with the posterior crescentic lobule of the hemisphere. Syn: declive; declivus.

folium vermis [L. folium—leaf] single folium that lies between the clivus anterior and superior to it and the tuber posterior and inferior to it and marks the posterior limit of the arbor vitae. It is continuous with the much expanded posterior superior lobule of the hemisphere.

tuber segment on the posterior inferior surface of the vermis, between the folium vermis and great horizontal fissure above it and the pyramis and postpyramidal fissure anterior and inferior to it. It is continuous with the posterior inferior and gracile lobules of the hemisphere. With the folium vermis and pyramis it lies at the base of the vallecula cerebelli

pyramis segment on the inferior surface of the vermis, separated from the uvula anterior to it by the prepyramidal fissure and from the tuber posterior and superior to it by the postpyramidal fissure, It is continuous with the biventer of the hemisphere.

uvula segment on the inferior surface of the vermis, separated from the

nodule anterior and superior to it by the postnodular fissure and from the

pyramis posterior to it by the prepyramidal fissure. It is continuous with the tonsil of the hemisphere.

nodule most caudal segment of the vermis, overlying the posterior medullary velum and separated from the uvula posterior and inferior to it by the postnodular fissure. It is connected to the flocculus of the hemisphere by the peduncle of the flocculus.

chamber, posterior space within the eyeball behind the cornea and in front of the iris.

cerebral /ser'e‑bral/ pertaining to the cerebrum. cerebral hemisphere see hemisphere, cerebral. cerebral palsy see palsy, cerebral. cerebral peduncle see peduncle, cerebral.

cerebrum /ser'e‑brum/ subdivision of the brain derived from the embryonic telencephalon and consisting of the pallium, basal ganglia, and certain other basal structures which are a part of the rhinencephalon. Syn: end brain. see also cortex. cerebral.

cerebrum, lobes

lobe, central see insula. Syn: island of Reil; isle of Tell.

lobe, fornicate [L. fornix—an arch] portion of the cerebral cortex which partially encircles the upper part of the brain stem and which comprises the cingulate gyrus, isthmus, hippocampus, parahippocampal gyrus, and uncus. It constitutes a part of the limbic lobe. Syn: fornicate gyrus.

lobe, frontal that portion of the cerebral hemisphere anterior to the central sulcus.

lobe, limbic subcallosal gyrus, anterior and posterior parolfactory gyri, olfactory bulb and stalk, medial and lateral olfactory gyri, cingulate gyrus, isthmus, hippocampus, parahippocampal gyrus, and uncus, and sometimes including the amygdala.

lobe, occipital posterior subdivision of the cerebrum separated from the parietal lobe on the medial surface of the hemisphere by the parietooccipital fissure, and from the temporal lobe by a line from the parietooccipital fissure to the occipital notch.

lobe, parietal subdivision of the cerebrum separated from the frontal lobe by the central sulcus, from the temporal lobe by the lateral fissure, and from the occipital lobe by the parietooccipital fissure.

lobe, temporal that portion of the cerebral hemisphere inferior to the lateral fissure.

cerebrum, lobules see gyrus, paracentral; lobules, inferior and superior parietal; precuneus.

chain ganglion see ganglion, chain.

chain neuron a series of two or more neurons, linked together consecutively so that an impulse may pass from one to the next throughout the series.

chamber, anterior space within the eyeball behind the cornea and in front of the lens.

posterior chamber space within the eyeball behind the iris and in front of the lens

chamber, vitreous space within the eyeball, behind the lens and containing the vitreous body. It communicates with the anterior chamber by way of the pupil.

Charcot, artery of see artery of Charcot.

Charcot, Jean Marie [1825‑1893] French neurologist, noted for his neurologic clinic at Salpetrière. He founded the Archives of Neurology in 1880.

chiasm [chiasma], optic [Gr. chiasma—two crossing lines, from the Greek letter chi] structure composed of crossing optic nerve fibers from the media] half of each retina, and fibers from the lateral half of each retina which continue into the homolateral optic tract without crossing the midline.

cholinergic pertaining to those fibers which release acetylcholine at their axon terminations. Cholinergic fibers include some [or all] fibers which synapse within the central nervous system; all autonomic preganglionic fibers; all posiganglionic parasympathetic fibers; and those postganglionic sympathetic fibers which supply sweat glands, some [or a] blood vessels which dilate upon sympathetic stimulation, and possibly uterine muscle.

cholinesterase enzyme which inactivates [hydrolyzes] acetylcholine.

chorda dorsalis see notochord.

chorda tympani branch which leaves the facial [intermediate] nerve in the facial canal, enters the tympanic cavity through the tympanic aperture of the chorda tympanic canal, passes between the short process of the incus and the neck of the malleus, leaves the tympanic cavity through the petrotympanic fissure, and joins the lingual nerve. It is composed of visceral sensory fibers for taste from the anterior two‑thirds of the tongue and preganglionic parasympathetic fibers from the superior salivatory nucleus of VII which, after synapse in the submandibular and Langley’s ganglia, supply motor fibers to the sublingual and submandibular glands, respectively.

chordoma growth derived from remnants of the notochord.

chorea [Gr. dance] sudden, jerky, involuntary movements, together with grimacing and faulty vocalization, resulting from a lesion of the caudate nucleus.

choreiform pertaining to chorea.

chorea, Huntington's progressive, hereditary disorder of adults, characterized by a choreiform motor disability and dementia.

choroid [chorioid] 1. that part of the vascular tunic of the eye interposed between the sclera and the retina. 2. pertaining to the choroid plexus. 3. pertaining to the choroid fissure.

chromatolysis series of nuclear and cytoplasmic changes which occur in the cell body of the neuron, as a result of injury to one of its processes or in response to other pathologic conditions.

chronaxie minimum time during which a current twice the rheobasic strength must flow in order to excite.

ciliary for ciliary body, crown, epithelium, and ganglion, see the nouns.

cingulate gyrus see sulcus, cingulate.

cingulum /sing'gu-lum/ [L. girdle] [B.N.A.1 association bundle of the cerebrum located within the cingulate gyrus. It has connections all along its course with adjacent frontal, parietal, and temporal lobe cortex. Syn: fornix periphericus. longitudinal fasciculus of the fornicate gyrus.

Cloquet, J. G. f 1790—1883] anatomist in Paris. The canal of Cloquet is the hyaloid canal of the developing eye.

cingulum ammonale old term for the association fibers interconnecting the hippocampus and parahippocampal gyrus.

cingulum limitans old term for the cingulum.

circle, arterial see circle of Willis.

circle of Willis arterial circle on the base of the brain formed by the internal carotid arteries, the anterior and posterior cerebral arteries, and the anterior and posterior communicating arteries.

circumflex nerve see nerve. axillary.

cistern[s] [cystern] portions of the subarachnoid space, in regions where arachnoid spans irregularities on the surface of the brain. see also cisterna, ambiens and magna.

cistern, cerebellomedullary that portion of the subarachnoid space caudal to the cerebellum and posterior to the medulla. Syn: cisterna magna.

cistern of the cerebellopontine angle that part of the subarachnoid space lateral to the brain stem in the region where the pons, medulla, and cerebellum meet and where the lateral aperture of the fourth ventricle communicates with the subarachnoid space.

cistern, circumesencephalic See cisterna ambiens.

cistern of the corpus callosum that part of the subarachnoid space above the corpus callosum and between the two cerebral hemispheres.

cistern, interpeduncular that part of the subarachnoid space between the bases of the two cerebral peduncles.

cistern of the lamina terminalis that part of the subarachnoid space anterior to the lamina terminalis.

cistern, lumbar that part of the subarachnoid space caudal to the spinal cord.

cistern, perimesencephalic see cisterna ambiens.

cistern, pontine that part of the subarachnoid space anterior and lateral to the pons

cistern, quadrigeminal See cistern, superior.

cistern, superior that part of the subarachnoid space dorsal to the midbrain and superior [rostral] to the cerebellum.

cisterna ambiens that part of the subarachnoid space lateral to the midbrain.

cisterna magna see cistern, cerebellomedullary.

Clarke, Jacob Augustus Lockhart [1817‑1880] English anatomist who described the dorsal nucleus of Clarke in 1851. see nucleus, dorsal, of Clarke.

Claudius, F. M. [1822‑1869] anatomist in Marburg. The cells of Claudius compose a single layer of cuboidal cells lying in the base of the external spiral sulcus of the cochlear duct.

claustrum [L. an enclosed space or barrier] thin sheet of gray matter interposed between the insula and extreme capsule laterally and the external capsule and the putamen medially; one of the basal ganglia.

clava /kli'va/ [L. club] protuberance on the dorsal surface of the medulla, overlying nucleus gracilis. Syn: gracile tubercle.

cleft, Lantermann see incisure of Schmidt‑Lantermann.

cleft of Schmidt‑Lantermann see incisure of Schmidt‑ Lantermann.

climbing fibers see fiber[s], climbing.

clivus /kli'vus/ [L. slope or hill] 1. subdivision of the cerebellar vermis between the culmen and folium vermis. Syn: declive; declivus. see cerebellum, lobules [vermis]. 2. Bony anterior wall of the posterior cranial fossa.

cochlea /kok'lo‑a/ [L. snail shell] subdivision of the internal ear concerned with hearing.

collateral eminence See eminence, collateral.

collateral ganglion see ganglion, collateral.

colliculus /col-ik'u-lus/ [L. mound] small protuberance.

colliculus, abducent see colliculus, facial.

colliculus abducentis see colliculus, facial.

colliculus, anterior see colliculus, superior.

colliculus, facial elevation on the floor of the fourth ventricle, media] to the sulcus limitans and overlying the abducent nucleus and genu of the facial nerve. Syn: abducent colliculus; eminentia teres.

colliculus, inferior rounded elevation on either side of the midline in the caudal part of the tectum on the dorsal surface of the midbrain. It is associated with the auditory system. Syn: posterior colliculus; lateral mesenchephalic nucleus, pars dorsalis.

colliculus, posterior See colliculus, inferior.

colliculus, superior rounded elevation on either side of the midline in the rostral part of the tectum on the dorsal surface of the midbrain. Syn: anterior colliculus. It is composed of alternating layers of cells and fibers, which, from superficial to deep, are as follows:

stratum zonale most superficial layer of the superior colliculus, composed chiefly of fibers of the external corticotectal tract from auditory association cortex in the occipitotemporal region.

stratum griseum superficiale layer of small nerve cells just deep to the stratum zonale of the superior colliculus. It receives fibers from the adjoining fibrous layers and discharges to the deeper layers of the superior colliculus. Syn: stratum cinereum.

stratum opticum layer of optic nerve fibers in the superior colliculus between the stratum griseum superficiale and stratum griseum intermediale. This layer is much reduced in primates, and especially in man.

stratum lemnisci the combined stratum griseum intermediale and stratum album intermediate of the superior colliculus.

stratum griseum intermediale layer of small nerve cells in the superior colliculus. Just superficial to and associated with the stratum album intermediale, and part of the stratum lemnisci. Syn: stratum griseum medium. stratum album intermediale main receptive layer of the superior colliculus, composed mainly of nerve fibers of the internal corticotectal tract from the occipital [area 18] and preoccipital [area 19] cortex, supplemented by fibers of the spinotectal tract, ventral secondary ascending tract of V, and nigrotectal and thalamotectal tracts. Syn: stratum album medium. stratum griseum profundum layer of intermediate‑sized and large nerve cells in the superior colliculus, just deep to the stratum album intermediale, and whose axons enter the underlying stratum album profundum.

stratum album profundum efferent layer of the superior colliculus at the edge of the periaqueductal gray, and including fibers of the medial and lateral tectospinal, tectorubral, tectooculomotor, tectonigral, tectopontine, tectotegmental, and tectohabenular tracts.

stratum griseum et fibrosum periventriculare periventricular gray around the cerebral aqueduct of the midbrain, composed of small to medium‑sized nerve cells and thinly medullated or unmedullated nerve fibers of the acousticooccipital tract and dorsal longitudinal fasciculus.

coloboma disorder arising from defective closure of the choroid fissure of the optic cup and consisting of a gap in the inferior part of the iris, ciliary body, retina, and choroid coat of the eye.

columella see pillar, anterior. of the fornix.

column see also tract; bundle; fasciculus; nucleus.

column, anterior 1. see funiculus, ventral. 2. see column, anterior gray.

column, anterior gray column of gray matter in the anterior portion of the spinal cord, containing the cell bodies of spinal cord motor neurons. When seen in cross sections of the spinal cord, this area constitutes the ventral horn.

column, central magnocellular cell cells of the dorsal funicular gray, nucleus proprius, in the dorsal horn of the spinal cord.

column of the fornix anterior pillar of the fornix.

column of the fornix, anterior See pillar of the fornix, anterior.

column of the fornix, posterior See pillar of the fornix, posterior.

column, pericornual magnocellular See nucleus, posterior marginal.

column, posterior 1. see funiculus, dorsal. 2. see column, posterior gray.

column, posterior gray column of gray matter in the posterior portion of the spinal cord containing the cell bodies of secondary sensory and other neurons. When seen in cross sections of the spinal cord, this area constitutes the dorsal horn.

column, spinal row or column of vertebrae and intervertebral discs, forming the support of the neck and trunk and enclosing the spinal cord. Syn: vertebral column.

column, vertebral See column, spinal.

columna fornicis [N.A.] See pillar, anterior, of the fornix.

comb bundle See tract, nigrostriate.

commissura fornicis See commissure, hippocampal.

commissura infima /ko“m‑ish'u‑ral in'fi‑ma/ fibers from fasciculus solitarius which cross the midline dorsal to the central canal near the junction of the brain and spinal cord. Syn: inferior commissure; dorsal white commissure; commissure of Haller.

commissural /kom‑ish'u‑ral/ pertaining to a commissure.

commissural fibers See fiber[s], commissural, of the cerebral hemispheres.

commissure /ko“m‑ish'u‑ral/ [L. commissure, from con or com —together and mittere—to put] bundle of nerve fibers which crosses the midline, usually connecting similar structures on the two sides. see also decussation.

commissure, anterior bundle of nerve fiber which crosses the midline in the upper part of the lamina terminalis and which consists primarily of interconnections between the olfactory bulbs, amygdaloid nuclei, anterior perforated substances, parahippocampal gyri, and parts of the neopallial cortex of the temporal lobe.

commissure, anterior cerebellar see commissure, superior cerebellar.

commissure, anterior hypothalamic see decussation, dorsal supraoptic.

commissure, anterior white see commissure, ventral white.

commissure, dorsal dorsal gray cellular area dorsal to the central canal in the upper part of the cervical spinal cord, consisting of the caudal fused portions of nucleus solitarius of the two sides.

commissure, dorsal supraoptic ventral supraoptic decussation or a combination of the dorsal and ventral supraoptic decussations.

commissure, dorsal white see commissura infima.

commissure of the fibrae ansulatae see decussation, dorsal supraoptic.

commissure of Forel see decussation, supramammillary.

commissure of the fornix see commissure, hippocampal.

commissure of Ganser see decussation, dorsal supraoptic

commissure, gray see massa intermedia.

commissure of Gudden most ventral of the supraoptic decussations, located within the substance of the optic chiasm and tracts or closely applied to their dorsal surface. Although absent in primates it is said to connect the medial geniculate nuclei in some species. Syn: ventral supraoptic commissure; intrachiasmatic decussation; ventral division of the inferior hypothalamic decussation.

commissure, habenular bundle of nerve fibers which crosses the midline through the upper attachment of the pineal body, between the two habenulae and through which the habenulae are connected mainly with subcortical centers of the opposite side.

commissure of Haller see commissura infima.

commissure of Held secondary auditory fibers from the ventral cochlear nucleus which cross the midline dorsal to the trapezoid body to enter the lateral lemniscus of the opposite side.

commissure, hippocampal commissure just beneath the splenium of the corpus callosum at the junction of the pillar and body of the fornix and consisting mostly of fornix fibers from the hippocampus of one side which enter the contralateral fornix for distribution with the fibers of the opposite side. Syn: commissura fornicis; commissure of the fornix.

commissure, Inferior see commissura infima.

commissure, lateral or cerebellar fibers which cross the midline in the cerebellum, in the region of the fastigial nucleus, and including [among others] cerebellospinal, cerebellovestibular and ventral spinocerebellar fibers. Syn: posterior cerebellar commissure.

commissure of the lateral lemniscus nerve fibers arising in the dorsal nucleus of the lateral lemniscus, which cross the midline and probably terminate in the contralateral nucleus of the lateral lemniscus, inferior colliculus, and medial geniculate nucleus, Syn: commissure of Probst.

commissure of Meynert see decussation, ventral supraoptic.

commissure, middle see massa intermedia.

commissure, posterior bundle of nerve fibers which crosses the midline at the junction of the midbrain and diencephalon and which is composed in part of fibers interconnecting the two pretectal nuclei and fibers from certain midbrain nuclei into the contralateral medial longitudinal fasciculus.

commissure, posterior cerebellar see commissure, inferior cerebellar.

commissure of Probst see commissure of the lateral lemniscus.

commissure, soft see massa intermedia.

commissure, superior cerebellar fibers which cross the midline in the rostral part of the cerebellum and containing, at least in part, association fibers which interconnect the cerebellar hemispheres.

commissure, superior hypothalamic see decussation, dorsal supraoptic.

commissure, supramammillary see decussation, supramammillary.

commissure, ventral supraoptic see commissure of Gudden.

commissure, ventral white fiber bundles crossing the midline between the central canal and the ventral median fissure of the spinal cord. Syn: anterior white commissure.

component, nerve the sum of all neurons having like anatomical and physiological characters so that they could act in a common mode [Herrick, 1918]. Such neurons may be afferent [sensory] or efferent [motor] in type and innervate structures of visceral or of somite origin.

conarium see body, pineal.

conduction, avalanche type of conduction, described for the cerebellar cortex, in which stimulation of a single neuron may fire many secondary neurons, each of which, in turn, may fire many tertiary neurons. [Ram6n y Cajal, 1911].

conduction, saltatory conduction in which a nerve impulse jumps from one node of Ranvier to the next along a nerve fiber.

cone color‑receptive photoreceptor of the retina. see also rod.

confluens sinuum [N.A.] place in the region of the internal occipital protuberance where the superior sagittal, straight, occipital, and transverse sinuses communicate. Usually the superior sagittal sinus continues into the right transverse sinus and the straight sinus continues into the left transverse sinus, with or without communication between the two systems.

connexus, interthalamic see massa intermedia.

conus medullaris [N.A.] caudal tapering portion of the spinal cord. Syn: conus terminalis

convolution [L. con—together, volere—to roll] elevation or ridge on the surface of the cerebral hemisphere, separated from other such elevations by a fissure or sulcus. Syn: gyrus.

convolution, abrupt see cuneus.

convolution, anterior ascending see gyrus, precentral.

convolution, ascending frontal see gyrus, precentral.

convolution, ascending parietal see gyrus, postcentral.

convolution, Broca's inferior frontal gyrus of the left cerebral hemisphere.

convolution, first frontal see gyrus, superior frontal.

convolution[s] of Gratiolet small convolutions buried beneath the lateral surface of the occipital lobe.

convolution[s], Heschl’s see gyrus, transverse temporal.

convolution, posterior ascending see gyrus, postcentral.

convolution, second frontal see gyrus, middle frontal.

convolution, subtemporal see gyrus, inferior temporal.

convolution, superfrontal see gyrus, superior frontal.

convolution, third frontal see gyrus, inferior frontal.

convolution, transisthmian isthmus of the fornicate lobe. See cerebrum, lobes.

convolution, Zuckerkandl’s see gyrus, subcallosal

copula see lamina rostralis.

cord, spinal elongated, thick‑walled, tubular subdivision of the central nervous system contained within the vertebral canal. Syn: medulla spinalis; myelon.

cornu ammonis [L. horn of Ammon] subdivision of the hippocampal formation consisting of a folded mass of cells. It is a 3‑layered cortex [molecular, pyramidal, polymorphic layers] further subdivided into 7 layers by Ramón y Cajal [1911]. Its cross sectional area was also secondarily subdivided in special fields [CA1‑CA4] by Lorente de Nó [1934]. Syn: hippocampus major; limbus corticalis. see also hippocampus, 2.

cornucopia extension of the choroid plexus into each lateral recess of the fourth ventricle. see also Bochdalek, V. A.

corona radiata [L. corona—crown] fibers of the cerebral white matter which emerge from the internal capsule and fan out as they approach the cerebral cortex.

corpora albicantia see body, mammillary.

corpora quadrigemina the four protuberances on the dorsal surface of the midbrain; the superior and inferior colliculi. see also tectum.

corpus [L. plural: corpora] body.

corpus callosum [L. callosus—hand] thick band of commissural fibers interconnecting corresponding areas of the neopallial cortex. It is subdivided into a genu, a rostrum, a body, and a splenium.

corpus callosum, body large midportion of the corpus callosum between the genu and the splenium.

corpus callosum, genu anterior portion of the corpus callosum.

corpus callosum, rostrum portion of the corpus callosum between the genu and the lamina rostralis.

corpus callosum, splenium posterior portion of the corpus callosum.

corpus cerebelli cerebellum exclusive of the flocculonodular lobe.

corpus dentatum see nucleus, dentate.

corpus fornicis [N.A.] see fornix, body.

corpus Luysi see nucleus, subthalamic.

corpus mammillare [N.A.] see body, mammillary.

corpus medullare of the cerebellum deep mass of white matter within the cerebellum.

corpus restiforme [B.N.A.] see peduncle, inferior cerebellar.

corpus striatum collective term for caudate nucleus, putamen, and globus pallidus.

corpus trapezoideum see body, trapezoid.

corpuscle, Golgi‑Mazzoni small, somewhat spherical nerve ending with a relatively thin capsule containing a coiled nerve fiber and thought to be a pressure receptor.

corpuscle, Melssner’s peanut‑shaped tactile nerve ending. located in the dermal papillae.

corpuscle, Pacinian nerve ending having a multilayered connective tissue capsule, located in subcutaneous connective tissue, mesentery, and other areas and thought to be sensitive to pressure.

corpuscle, Ruffini elongated cylindrical nerve ending having a thin capsule containing connective tissue and nerve fibers. Those in the subcutaneous connective tissue are thought to be receptors for warmth.

corpuscle of Vater‑Pacini see corpuscle, Pacinian.

cortectomy removal of the cortex of a cerebral hemispheres.

cortex, cerebellar cortex, cerebellar superficial

mantle of gray matter of the cerebellum. The layers of the cerebellar cortex are as follows:

molecular layer most superficial layer of the cerebellar cortex, composed

largely of the dendrites of Purkinje cells, other nerve cell processes and

relatively few cell bodies, a synaptic zone. Syn: plexiform layer.

Purkinje cell layer layer of large cell bodies arranged singly between the molecular and granular layers of the cerebellar cortex.

granular layer innermost layer of the cerebellar cortex, composed largely of the closely packed granule cells.

cortex, cerebral superficial mantle of the gray matter of the cerebral hemispheres. See also areas, Brodmann's. The layers of the cerebral cortex, based on the cytoarchitectonic patterns by Brodmann, Campbell, and Cajal and on the myeloarchitectonic pattern by the Vogts, are as follows:

cortex, agranular [L. cortex—outer layer, bark] neopallial cortex in which the granular layers are reduced, e.g., motor cortex.

cortex, auditory cortex of the transverse temporal gyri on the opercular surface of the temporal lobe; Brodmann's areas 41 and 42.

cortex, calcarine see cortex, visual.

cortex, cerebral .

layer I most superficial layer of the cerebral cortex, a synaptic zone, but including the horizontal cells of Cajal:

lamina molecularis [Brodmann];

plexiform layer [Campbell];

plexiform or molecular layer [Cajal];

lamina tangentialis [Vogt].

layer II composed of small pyramidal cells and many small stellate cells, and

containing the stripe of Kaes:

lamina granularis externa [Brodmann;

layer of small pyramids [Campbell];

layer of small pyramidal cells [Campbell];

lamina dysfibrosa [Vogt].

layer III composed of medium‑sized and large pyramidal cells and some small stellate cells:

lamina pyramidalis [Brodmann];

layer of medium‑sized and large pyramids [Campbell];

layer of medium‑sized and large pyramidal cells [Cajal];

lamina suprastriata [Vogt].

layer IV composed mainly of small stellate or granule cells and containing the outer stripe of Baillarger:

lamina granularis interna [Brodmann];

granular layer [Campbell];

layer of small stellate and pyramidal cells [Cajal];

stria Baillarger externa [Vogt].

layer V composed of large and medium‑sized pyramidal cells with intermingled stellate cells, and in the motor area, giant pyramidal or Betz cells. The inner stripe of Baillarger runs through this layer:

lamina ganglionaris [Brodmann];

inner layer of large pyramids [Campbell];

layer VI cortex containing cells, varied in shape, of a modified pyramidal type. Cajal divided this innermost layer into two layers. see his layer VII below:

deep layer of large pyramidal cells [Cajal];

lamina infrastriata superficialis and stria Baillarger interna [Vogt].

lamina multiformis [Brodmann];

spindle cell layer [Campbell];

layer of medium‑sized pyramidal and triangular cells [Cajal];

lamina infrastriata [Vogt].

layer VII layer of fusiform cells [Cajal].

cortex, eulaminate see cortex, homotypic.

cortex, frontal see cortex of the frontal lobe.

cortex, heterogenetic see allocortex. In addition to the cortices of the archipallium and paleopallium, Brodmann included other areas of the rhinencephalon.

cortex, heterotypic neopallial cortex in which the six layers are obscure, e.g., motor cortex.

cortex, homogenetic six‑layered cortex of the neopallium. Syn: isocortex.

cortex, homotypic neopallial cortex in which the six layers are clearly evident, e.g., sensory cortex.

cortex, insular cortex of the insula, which exerts descending control on brainstem autonomic centers..

cortex, limitrophic see cortex, transitional.

cortex, motor cortex in the precentral gyrus, containing giant pyramidal cells. Syn: Brodmann's area 4.

cortex, occipital cortex of the occipital lobe involved in visual perception.

cortex, parietal cortex of the parietal lobe, implicated in perception of body position in three dimensional space..

cortex, preoccipital see area, peristriate. Higher-order visual cortex.

cortex, projection cerebral cortex which receives fibers fr6m, or sends fibers to, subcortical regions.

cortex, somesthetic sensory cortex in the postcentral gyrus of the cerebrum. Syn: Brodmann's areas 3, 1, and 2; somesthetic area.

cortex, temporal cortex of the temporal lobe implicated in hearing and memory.

cortex, transitional cortex in a region where one type borders on another. Syn: limitrophic cortex.

cortex, visual cortical area concerned with the perception of visual stimuli. Syn: Brodmann's area 17; striate area; visual projection cortex; calcarine cortex.

Corti, Marchese Alfonso [1822‑1888] Italian histologist noted for his investigations of the mammalian cochlea, published in 1851. see ganglion, spiral, organ of Corti; tunnel of Corti.

corticifugal /kor-ti“-sif’u“-gal/ carrying impulses away from the cerebral cortex, e.g., as in the corticospinal tract or in corticothalamic projections Syn: corticofugal [preferred].

corticipetal /kor-ti“-is“p’etal/ carrying impulses toward the cerebral cortex.

cortilymph fluid contained within the tunnel of Corti.

Cotugno, Domenico [1736‑1822] Italian anatomist, professor of anatomy at Naples, noted for his studies of the ear, including a description of the labyrinthine system and its fluids [1761]. He also published the first description of the cerebrospinal fluid [1764]. His name is sometimes Latinized to Cotunnius. see aqueduct of Cotunnius; perilymph.

Cotunalus see Cotugno.

crest, ganglionic see crest, neural.

crest, neural cells of ectodermal origin, adjacent to the dorsal portion the neural tube, which become segmentally clustered and from which develop sensory ganglion cells, some autonomic ganglion cells, and certain other structures.

crista acustica see crista ampullaris.

crista ampullarls [ L. crista‑crest] ridge which projects into the lumen of each membranous ampulla at right angles to the plane of the semicircular duct and which constitutes a sensory end organ for kinetic equilibrium.

crocodile tears see tears, crocodile.

crook, shepherd's axon which arises from the dendrite of a nerve cell in the superior colliculus, and which forms a loop before entering the stratum album profundum to leave the superior colliculus.

crown, ciliary sum of the ciliary processes on the posterior surface of the ciliary body.

crus, cerebral [L. crus—leg] see peduncle, cerebral.

crus cerebri [N.A.] see peduncle, cerebral.

crus, common see crus commune.

crus commune channel of the membranous labyrinth, by which the superior and posterior semicircular ducts Communicate with the ventricle.

crus fornicis [N.A.] see pillar of the fornix, posterior.

Cruvelhier’s nerve see nerve, vertebral.

Cruveilhier’s plexus see plexus Cruveilhier's.

CSF see fluid, cerebrospinal.

culmen .A.] subdivision of the anterior lobe of the cerebellar vermis between the central and the clivus. see cerebellum, lobules [vermis].

cuneus [L. wedge] wedge‑shaped segment of the occipital lobe on the medial surface of the cerebrum between the calcarine and parietooccipital fissures. Syn: abrupt convolution.

cupula dome‑ or cup‑shaped structure surmounting the crista ampullaris, into which the hairs from the crista project.

Cushing, Harvey [1869‑1939] American surgeon of Johns Hopkins, Harvard, and Yale Universities, who contributed greatly to the practice of neurosurgery.

Cushing's loop temporal loop of the optic radiation.

cystern see cistern; cisterna,

cytoarchitectonic pertaining to the cytoarchitecture of the central nervous system; subdivision of nuclei or cortical areas on the basis of myelin, cell, and/or other neurohistological methods, often in conjunction with electrophysiology.

cytoarchitectonics see cytoarchitecture.

cyton [cytone] see body, cell.

d

Darkschewitsch, nucleus nucleus of the posterior commissure.

decerebration disconnection or removal of the brain of a living animal.

declive [declivus] [L. declivus—sloping] see clivus, 1; cerebellum, lobes [vermis]. decortication removal of all or part of the cerebral cortex.

decussation [L. decussare—to intersect, from decussate, represented by ´] place where nerve fibers cross the midline, or the nerve fibers which take part in the crossing. see also commissure.

decussation, anterior hypothalamic see decussation, dorsal supraoptic.

decussation, dorsal supraoptic most dorsal of the supraoptic decussations. It presumably contains pallidohypothalamic fibers which arise from the medial segment of the globus pallidus, arch over the fornix, cross the midline in the floor of the third ventricle, and terminate in the ventromedial nucleus of the hypothalamus, although some fibers may end homolaterally. Some fibers extend into the midbrain. Syn: anterior [or superior] hypothalamic decussation [or commissure]; commissure of Ganser; commissure of the fibrae ansulatae; dorsal division of the dorsal supraoptic commissure.

decussation, dorsal tegmental fibers of the tectorubral and medial tectobulbar and tectospinal tracts which cross the midline at upper midbrain levels. Syn: decussation of Meynert; fountain decussation.

decussation of Forel see decussation, ventral tegmental.

decussation, fountain see decussation, dorsal tegmental.

decussation, inferior hyp6thalamic ventral supraoptic decussation or a combination of the ventral supraoptic decussation and the commissure of Gudden.

decussation, intrachiasmatic see commissure of Gudden.

decussation of the medial lemnisci see decussation, sensory.

decussation of Meynert see decussation, dorsal tegmental.

decussation, motor crossing of the pyramidal tract fibers—from the pyramid of the medulla to the lateral funiculus of the spinal cord.

decussation, posterior hypothalamic see decussation, supramammillary

decussation, postmammillary see decussation, supramammillary.

decussation, pyramidal see decussation, motor.

decussation, sensory crossing of fibers from nucleus gracilis and nucleus cuneatus of each side to form the medial lemnisci, and consisting of secondary sensory fibers carrying impulses for sense of position, vibratory sensibility, and tactile discrimination to nucleus ventralis posterolateralis of the dorsal thalamus. Syn: superior pyramidal decussation; decussation of the medial lemnisci.

decussation, superior hypothalamic see decussation, dorsal supraoptic.

decussation, superior pyramidal see decussation, sensory.

decussation, suprachiasmatic see decussation, ventral supraoptic.

decussation, supramammillary fibers which cross the midline, dorsal to the mammillary bodies, at the junction of the hypothalamus and midbrain tegmentum. It consists of fibers connecting various diencephalic and midbrain nuclei, including hypothalamotegmental bundles, connections between the two subthalamic nuclei, and others. Syn: commissure of Forel; posterior hypothalamic decussation, postmammillary decussation.

decussation, supraoptic any of several fiber bundles which cross the midline in the floor of the third ventricle, in conjunction with or dorsal to the optic chiasm, particularly the dorsal and ventral supraoptic decussations, and in subprimates the commissure of Gudden. They are said to connect portions of the basal ganglia, diencephalon, and midbrain with portions of such areas of the other side.

decussation, trochlear decussation of the trochlear nerve [cranial nerve IV] in the anterior medullary velum, at the junction of the Pons and midbrain.

decussation, ventral supraoptic largest of the supraoptic decussations, located on t4e dorsal surface of the optic chiasm and tracts. It presumably contains fibers which arise from the subthalamic nucleus, pass through the internal capsule, and terminate in the contralateral globus pallidus. Some fibers are said to extend into the midbrain. Syn: commissure of Meynert; dorsal supraoptic commissure or its ventral division; suprachiasmatic decussation. see also decussation, inferior hypothalamic.

decussation, ventral tegmental decussation of the rubrospinal tracts in the upper midbrain tegmentum. Syn: decussation of Forel.

decussation of Wernekinck decussation of the superior cerebellar peduncle.

degeneration, ascending degeneration of axons and myelin sheaths of ascending tracts, progressing rostrally from the site of injury.

degeneration, descending degeneration of axons and myelin sheaths of the descending tracts, progressing caudally from the site of injury.

degeneration, retrograde degeneration from the axon terminals toward the cell body of a neuron after injury to its axon.

degeneration, secondary see degeneration. Wallerian.

degeneration, transneuronal degeneration of neurons after destruction of the neurons from which they receive their stimulation. Syn: transsynaptic degeneration.

degeneration, transsynaptic see degeneration, transneuronal.

degeneration, Wallerian complete degeneration of the axis cylinder, myelin sheath, and nerve endings of nerve fibers after injury to or separation from their cell bodies. Syn: secondary degeneration.

Deiters, Otto Friedrich Karl [1834‑1863] German anatomist, a pupil Virchow’s and noted for his studies of the ear and of the nervous system. The cells of Deiters are the outer phalangeal cells of the organ of Corti. The nucleus of Deiters is the lateral vestibular nucleus, which he described in 1865, or the lateral and vestibular nuclei taken together. The ventrolateral vestibulospinal tract is sometimes called the Deiterospinal tract.

Dejerine, Joseph Jules 1849‑1917] French neurologist. The tract of Dejerine is the ventral spinothalamic tract.

démarche de coq high‑stepping walk characteristic of certain cerebellar lesions.

demyelination pathologic process whereby myelinated nerve fibers lose their myelin sheaths.

dendraxon single process of a unipolar neuron, which divides into two branches, one of which conducts impulses toward the cell body and the other away from it.

dendrite [Gr. dendron—tree] process of a neuron which conducts impulses toward the cell body. Syn: dendron.

dendrite, apical process, typically large, extending from the apex of a cortical pyramidal cell toward the surface of the cerebral cortex.

dendrite, basilar process extending horizontally from the base of a pyramidal cell of the cerebral cortex.

dendron see dendrite.

dentate having a scalloped edge or a tooth-like configuration. see gyrus; ligament; nucleus.

dermatome cutaneous or other tissue area innervated by fibers of a particular spinal nerve.

Descemet, Jean [1732‑1810] French surgeon, professor of anatomy and surgery at Paris. He described the posterior elastic membrane of the cornea [Descemet’s membrane] in 1758, although it is said to have been first described by B. Duddell, an English oculist.

descendens cervicalis bundle of nerve fibers which arises from spinal cord segments C₂ and C₃. It joins the descendens hypoglossi to form the ansa cervicalis in the cervical plexus to supply certain muscles of the neck.

descendens hypoglossi bundle of nerve fibers not from the hypoglossal nerve as the name implies but from the cervical spinal cord segment C_l. It joins the descendens cervicalis to form the ansa cervicalis in the cervical plexus to supply certain muscles of the neck.

diaphragma sellae ring of dura mater around the pituitary stalk and separating the pituitary gland from the hypothalamus.

diastematomyelia abnormality in which the spinal cord is doubled.

diencephalon [Gr. dia or di—through; enkephalos—brain] most caudal subdivision of the forebrain consisting of the dorsal thalamus and metathalamus, ventral thalamus, hypothalamus, and epithalamus. Syn: 'tweenbrain; interbrain.

diplegia paralysis of two corresponding extremities or both sides of the face.

diplopia double vision.

disc, optic pale circular area of the fundus of the eye where the optic nerve fibers leave the retina.

disc, tactile see Merkel, F. S.

DOPA see L‑DOPA.

Dopamine an intermediary compound in the synthesis of norepinephrine. It 'is released largely, but not exclusively, by fibers of the nigrostriate tract.

dorsal 1. pertaining to the back. 2. thoracic.

Doyère, eminence of see eminence of Doy6re.

duct, cochlear spiral tube of the membranous labyrinth, within the bony cochlea and attached to its outer wall. It is bounded by the vestibular membrane, the basilar membrane, and the spiral ligament. Syn: scala media.

duct, endolymphatic narrow channel in the vestibular aqueduct, connecting the utriculosaccular duct and the endolymphatic sac of the membranous labyrinth. Syn: otic duct.

duct, otic see duct, endolymphatic.

duct, perilymphatic connective tissue spaces in the cochlear canaliculus, through which the scala tympani communicates with the subarachnoid space near the jugular bulb.

duct, periotic see duct, perilymphatic.

duct[s], semicircular three pairs of membranous tubes [superior, posterior, and lateral] contained within the semicircular canals of the bony labyrinth. Oriented at right angles to one another, they connect by five openings with the utricle of the internal ear.

duct, saccular narrow channel which connects the saccule and the endolymphatic duct.

duct, utricular duct narrow channel which connects the utricle and the endolymphatic sac.

duct, utriculosaccular narrow channel which connects the utricle and saccule of the membranous labyrinth of the internal ear with the endolymphatic duct.

ductus reuniens narrow channel of the membranous labyrinth, which connects the cochlear duct and the saccule.

dura mater [L. dura—hard or strong; mater—mother] outermost and heaviest layer of the meninges covering the brain and spinal cord Syn: pachymeninx

dust, ear see otolith[s].

dysarthria faulty articulation of consonant and vowel sounds.

dysdiadochokinesis cerebellar disorder characterized by an impaired ability to perform rapidly alternate contractions of antagonistic muscles, as in finger tapping or alternate pronation and supination of the hands.

dysmetria disorder in the control of the range of movement, characteristic of certain cerebellar lesions.

dysphagia difficulty in swallowing.

dysphonia impaired vocalization.

e

ear dust see otolith[s].

ecchondrosis physallphora remnant of the rostral end of the notochord, from which an intracranial chordoma may arise.

ectoderm [Gr. ektos—outside; derma—skin] outer layer of the embryo from which the nervous system develops.

Edinger, Ludwig [1855‑1918] German anatomist. The Edinger‑ Westphal nucleus [q.v.] of the oculomotor nerve was described in 1885. Edinger’s tract is the lateral spinothalamic tract.

EEG electroencephalogram; electroencephalographic. Invented by Hans Berger in 1929, a method for the gross extracranial recording of brain potentials

efferent [L. effere—to carry out from; from ex—out; from, ferre—to carry]; conducting away.

efferent neuron see neuron, efferent.

Ehrenritter, J. [d. 1790] Viennese anatomist. Ehrenritter’s ganglion is the superior petrosal ganglion of the glossopharyngeal nerve.

element of Fanañas see cell of Fanañas.

emboliform nucleus see nucleus, emboliformis.

eminence, collateral eminence on the medial wall of the posterior portion of the inferior horn of the lateral ventricle, overlying the collateral sulcus.

eminence of Doyère slight elevation of the muscle tissue at the point of termination of a motor nerve fiber.

eminence, medial ridge on the floor of the fourth ventricle, on each side of the midline between the median sulcus and the sulcus limitans, and extending the length of the pons

eminence, median that portion of the floor of the third ventricle at the point where the pituitary stalk attaches and which is composed of neurohypophysial tissue.

eminentia teres see colliculus, facial.

eminentia trigemini see tuberculum cinereum.

encephalocele abnormality in which the brain is herniated through an opening in the cranium.

encephalon [Gr. enkephalos—brain; from en—in; kephale—head] brain.

end brain see cerebrum: telencephalon.

end bulb of Held see neuropodium.

end bulb of Krause spherical nerve ending with a thin capsule containing a highly coiled nerve fiber. It is thought to be a cold receptor.

end foot see neuropodium.

ending, anulospiral primary nerve ending around the nuclear bag in a muscle spindle. It is a subtype of stretch receptor.

ending, Golgi see spindle, neurotendinous.

ending, nerve specialized termination at the end of a nerve fiber, composed of a branching or otherwise modified neural process and often including components of other tissues, such as connective tissue or muscle.

ending, neurotendinous see spindle, neurotendinous.

ending, Ruffini nerve ending thought to be sensitive to warmth.

endolymph fluid secreted by the stria vascularis of the cochlear duct, which fills the cavities of the membranous labyrinth. Syn: otic fluid: Scarpa’s fluid.

endoneurium interstitial, mesodermal, connective tissue within a nerve fascicle, or within a ganglion. Syn: epilemma; sheath of Henle.

enlargement, cervical enlarged portion of the spinal cord consisting of the last four cervical and first thoracic cord segments, associated with the brachial plexus and the innervation of the upper extremities.

enlargement, lumbosacral enlarged portion of the spinal cord, consisting of the last four lumbar and the first three sacral cord segments, associated with the lumbosacral plexus and the innervation of the lower extremities.

ependyma [Gr. epi—upon; endyma—garment] cellular lining of the ventricular spaces of the central nervous system.

ependymal 1. pertaining to the ependyma of the adult central nervous system. 2. pertaining to the ependymal layer of the developing central nervous system.

epicritic pertaining to fine intensity and spatial discriminatory ability.

epidural overlying the dura mater.

epilemma see endoneurium.

epineurium loose connective tissue which binds together two or more fasciculi of a peripheral nerve or which supports a ganglion.

epiphysis cerebri see body, pineal.

epithalamus dorsal, posterior portion of the diencephalon, composed of the habenula and its fiber bundles, the pineal body, the posterior commissure, and the tela choroidea of the third ventricle.

epithelium, ciliary two‑layered cuboidal epithelium covering the ciliary body and continuous anteriorly with the posterior epithelium of the iris and posteriorly with the retina. The layer on its free surface secretes aqueous humor. The deep layer is pigmented.

exencephaly abnormality in which the brain projects through the cranial roof.

Exner, S. [1846‑1926] Viennese physiologist. Exner’s writing center is located in the posterior portion of the middle frontal gyrus.

external capsule see capsule, external.

exteroception [adj. exteroceptive] that class of impulses arising from sensory end organs at or near the surface of the body and which relate the individual to the outside world.

extraaxial outside the central nervous system.

extramedullary outside the central nervous system.

extrapyramidal system see system, extrapyramidal.

extreme capsule see capsule, extreme.

eye fields portions of the cerebral cortex which, when stimulated, produce eye movements. see field[s], frontal and occipital eye.

f

facial see nerve; nucleus; and colliculus.

factors, releasing see releasing factors.

falx cerebelli [L.] Sickle-shaped narrow dural fold between the two cerebellar hemispheres.

falx cerebri cerebri sickle‑shaped dural fold located between the two cerebral hemispheres.

Farabeuf’s triangle triangular space outlined by the internal jugular veins, the hypoglossal nerve, and the common facial vein.

fascia dentata [L. fascia—ribbon or band] see gyrus, dentate.

fascia, dentate see gyrus, dentate.

fascia, Tarin’s see gyrus, dentate.

fasciculus [L. small bundle] bundle of nerve fibers within the central nervous system. see also tract; bundle; column; fibers.

fasciculus, anuloolivaris see tract, central tegmental.

fasciculus, arcuate see fasciculus. superior longitudinal.

fasciculus cuneatus [N.A.] tract in the lateral part of the posterior funiculus of the cervical and thoracic spinal cord and closed medulla. These fibers, with cell bodies in dorsal root ganglia, conduct impulses from tactile and proprioceptive endings in the upper half of the body primarily to the cuneate and lateral cuneate nuclei. Syn: Burdach's tract; funiculus cuneatus.

fasciculus, dorsolateral spinal cord tract located superficial to the tip of the dorsal horn and composed of short pain and temperature fibers which are processes of neurons having their cell bodies in the dorsal root ganglia. Syn: Lissauer’s tract; zona terminalis.

fasciculus, dorsal longitudinal bundle located just ventral to the floor of the cerebral aqueduct and fourth ventricle and composed of fibers mainly from the hypothalamus and dorsal tegmental nucleus to all cranial preganglionic parasympathetic nuclei and brain stem motor nuclei other than those innervating the ocular muscles. Syn: fasciculus or tract of Schütz; periependymal fasciculus.

fasciculus of Gowers see tract, ventral spinocerebellar.

fasciculus gracilis [L. gracilis—slender] [N.A.] tract occupying most of each half of the posterior funiculus in the lower spinal cord and the medial portion in the upper spinal cord and closed medulla. These fibers, with cell bodies in dorsal root ganglia, conduct impulses from tactile and proprioceptive nerve endings in the lower half of the body, primarily to nucleus gracilis. Syn: funiculus gracilis; tract of Goll.

fasciculus, inferior frontooccipital association bundle of the cerebrum, located along the inferior portion of the extreme capsule, dorsal to the uncinate fasciculus, It interconnects cortex of the lateral or inferolateral portion of the frontal lobe and cortex of the occipital lobe, with connections along the way, including the inferior temporal and fusiform gyri of the temporal lobe.

fasciculus, inferior longitudinal association bundle of the cerebrum which interconnects occipital lobe cortex and temporal lobe cortex in the inferior and lateral portion of the hemisphere. Syn: external sagittal stratum.

fasciculus, inferior occipitofrontal see fasciculus, inferior frontooccipital.

fasciculus interfascicularis tract located in the rostral half of the spinal cord between fasciculus gracilis and fasciculus cuneatus, composed of short, descending tactile and proprioceptive collaterals of fibers in fasciculus cuneatus. Syn: comma tract. tract of Schultze; semilunar fasciculus.

fasciculus interstitiospinalis of Muskegs the extrapyramidal or conditioning component of the medial longitudinal fasciculus. Its fibers arise from cells in the nucleus of the, posterior commissure and interstitial nucleus and end in motor nuclei of the brain stem and cervical spinal cord.

fasciculus, lateral occipital association bundle of the cerebrum which passes vertically through the occipital lobe and interconnects the fusiform gyrus of the temporal lobe and the posterior part of the parietal lobe. Syn: fasciculus of Wernicke; perpendicular or vertical occipital fasciculus.

fasciculus, lenticular fiber tract arising in the lentiform nucleus, passing dorsal to the subthalamic nucleus and terminating in the nucleus of the posterior commissure, interstitial nucleus of the medial longitudinal fasciculus and the large‑celled portion of 1he red nucleus. Syn: dorsal division of the ansa lenticularis; H₂ field of Forel.

fasciculus, longitudinal, of the fornicate gyrus see cingulum.

fasciculus, medial longitudinal fiber tract extending from the midbrain tegmentum into the cervical spinal cord, located close to the midline just ventral to the gray beneath the ventricular surface, composed of a vestibular component of fibers from vestibular nuclei to eye and neck muscle nuclei, an internuclear component interconnecting brain stem motor nuclei, and a conditioning component of fibers from certain midbrain nuclei to motor nuclei of brain stem and cervical cord. Syn: medial longitudinal bundle; posterior longitudinal fasciculus or bundle.

fasciculus, medial triangular sacral portion of the septomarginal fasciculus.

fasciculus of Meynert see tract, habenulointerpeduncular.

fasciculus, oval lumbar portion of the septomarginal fasciculus.

fasciculus, periependymal see fasciculus, dorsal longitudinal.

fasciculus, perpendicular occipital, of Wernicke see fasciculus, lateral occipital.

fasciculus, posterior longitudinal 1. usually medial longitudinal fasciculus; 2. sometimes dorsal longitudinal fasciculus.

fasciculus, predorsal see tract, medial tectospinal.

fasciculus proprius white matter immediately adjacent to the gray matter of the spinal cord. and composed of short fibers interconnecting neighboring spinal cord levels. Syn: ground or reflex bundle, propriospinal or spinospinal tract.

fasciculus retroflexus see tract, habenulointerpeduncular.

fasciculus, Russell's see fasciculus, uncinate, 1.

fasciculus of Schütz see fasciculus, dorsal longitudinal.

fasciculus, semilunar see fasciculus interfascicularis.

fasciculus, septomarginal tract located in the caudal half of the spinal cord between fasciculus gracilis and the dorsal median septum and composed of short descending tactile and proprioceptive collaterals of fibers in fasciculus gracilis At lumbar levels the septomarginal fasciculus is located along the mid‑portion of the septum, Syn: oval bundle‑, tract of Flechsig. At sacral levels the fasciculus i located at the dorsal surface. Syn: medial triangular fasciculus; triangular fasciculus; triangular field of Gombault and Philippe.

fasciculus solitarius fiber tract composed of descending fibers of the general visceral afferent component of the facial, glossopharyngeal, and vagus nerves. Syn Gierke's respiratory bundle.

fasciculus subcallosus see fasciculus, superior frontooccipital.

fasciculus, subthalamic fiber tract arising in the lentiform nucleus and terminating in the subthalamic nucleus, zona incerta, and midbrain tegmental gray. Syn intermediate division of the ansa lenticularis.

fasciculus, sulcomarginal area adjacent to the ventral median fissure in the ventral funiculus of the spinal cord, and composed mostly of cerebellospinal fibers which constitute the spinal component of the uncinate fasciculus.

fasciculus, superficial anterolateral see tract, ventral spinocerebellar.

fasciculus, superior frontooccipital association bundle of the cerebrum located along the caudate nucleus medial to the interdigitating fibers of the interna capsule and corpus callosum. Its fibers interconnect the cortex of the occipital and temporal lobes on the one hand with that of the frontal lobe and insula, on the other. Syn: fasciculus subcallosus, superior occipitofrontal fasciculus.

fasciculus, superior longitudinal association bundle of the cerebrum located along the dorsolateral border of the putamen, lateral to the internal capsule. It underlies and interconnects the cortices of the frontal, parietal, and occipital lobes and arches inferiorly and anteriorly with connections in the temporal lobe cortex. Syn: arcuate fasciculus.

fasciculus, superior occipitofrontal see fasciculus, superior frontooccipital.

fasciculus, thalamic fiber tract arising in the lentiform nucleus, passing dorsal to the zona incerta, and terminating primarily in nucleus ventralis anterior of the dorsal thalamus. It corresponds to part or all of the H₁ field of Forel.

fasciculus [i], transverse occipital two association bundles of the occipital lobe; one connects the upper lip of the calcarine fissure with the superolateral occipital cortex, the other connects the inferior lip of the calcarine fissure with the inferolateral occipital cortex.

fasciculus, triangular sacral portion of the septomarginal fasciculus.

fasciculus, uncinate [L. uncinatus—hook‑shaped] 1. fibers which arise in the fastigial nucleus of the cerebellum, cross the midline, loop around the superior cerebellar peduncle, join the inferior cerebellar peduncle, and terminate in the vestibular nuclei and in the ventral horn of the cervical spinal cord. Syn: hook bundle, Russell's fasciculus. 2. association bundle of the cerebellum interconnecting the cortex of the uncus and temporal pole with the cortex of the inferior frontal region.

fasciculus vertical occipital see fasciculus, lateral occipital.

fasciculus of Vialet association fibers which connect the inferior lip of the calcarine fissure with the inferolateral occipital cortex; one of the transverse occipital fasciculus.

fasciola cinerea strands of hippocampal tissue [usually dentate gyrus] which extend from the hippocampus, posterior to the splenium, into the induseum griseum above the corpus callosum. Syn: gyrus fasciolaris.

fastigial nucleus see nucleus, fastigial.

fastigium /fas-ti“dj' iu“m/ [L. summit] mid‑dorsal apical portion of the fourth ventricle.

fenestra cochleae see window, cochlear.

fenestra ovale see window, vestibular,

fenestra vestibuli see window, vestibular.

festination acceleration of gait with an inability to slow down or stop, characteristic of extrapyramidal dysfunction, as in Parkinson's syndrome.

fiber see fiber, nerve. see also bundle; fasciculus; tract.

fiber[s], aberrant pyramidal fibers which leave the pyramidal tract at brain stem levels, to descend with the medial lemniscus and terminate in motor nuclei of the brain stem and cervical spinal cord.

fiber[s], arcuate short association fibers which lie immediately beneath the cortex adjacent to a cerebral sulcus and which connect adjacent gyri. Syn: U‑fibers.

fiber[s], association, of the cerebral hemispheres nerve fibers which interconnect cortical regions of the same cerebral hemisphere, first described by Meynert.

fiber, band multinucleated syncytial cord formed by the proliferation of neurolemma sheath cells as a part of the regenerative process 6f peripheral nerve fibers. Syn: band of Büngner; Bandfasern.

fiber[s], basilar see strings, auditory.

fiber[s], cerebellomotorius fibers that arise in the cerebellum and terminate in motor nuclei of the brain stem.

fibers climbing olivocerebellar and perhaps other nerve fibers which enter the molecular layer of the cerebellar cortex and spiral around the dendritic processes of Purkinje cells.

fiber[s], commissural, of the cerebral hemispheres nerve fibers which cross the midline and interconnect similar cortical regions in the two cerebral hemispheres.

fiber[s], dorsal external arcuate see fiber[s], dorsal superficial arcuate.

fiber[s], dorsal superficial arcuate fibers that arise in the lateral cuneate nucleus, and enter the inferior cerebellar peduncle to terminate in the vermis of the cerebellum; fibers of the cuneatocerebellar tract.

fiber[s], external arcuate see fibers], dorsal and ventral superficial arcuate.

fiber[s], gamma efferent fine axons from small nerve cell bodies in the ventral horn, which terminate on the small, intrafusal muscle fibers within neuromuscular spindles. see also loop, gamma.

fiber[s] of Held nerve fibers which were thought to arise in the superior olivary nucleus and terminate in the dorsal cochlear nucleus.

fiber[s], internal arcuate fibers which arise in the gracile and cuneate nuclei, arch ventrally and medially in the medulla, and cross the midline in the sensory decussation. Most of the fibers join the medial lemniscus; some continue to synapse in the arcuate nucleus adjacent to the pyramid.

fiber[s], itinerant see fibers, projection.

fiber[s], intrafusal thin muscle fibers within a muscle spindle.

fiber[s], mossy axon terminals of fibers mainly of the pontocerebellar, vestibulocerebellar and spinocerebellar tracts, which terminate as rosettes in relation to the claw‑shaped dendrites of granule cells in the granular layer of the cerebellum. fiber, nerve process or a neuron together with its sheaths.

fiber[s], orbitofrontal association fibers of the cerebrum which pass through the anterior portion of the extreme capsule and interconnect the posterior part of the orbital gyri and the dorsolateral portion of the frontal lobe.

fiber, parallel axon of a granule cell of the cerebellar cortex, which courses through the molecular layer in a plane parallel to the longitudinal axis of a cerebellar folium.

fiber[s] of passage nerve fibers which pass through a region without synapse.

fiber[s] of Piccolomini striae medullares of the fourth ventricle.

fiber[s], projection nerve fibers which connect cortical areas of the cerebrum with subcortical regions.

fiber[s], propriospinal nerve fibers that arise and terminate wholly in the spinal cord; intrinsic spinal fibers.

fiber of Remak see C‑fiber.

fiber[s], Stilling’s short association fibers of the cerebellum.

fiber[s], superficial arcuate see fibers. dorsal and ventral superficial arcuate.

fiber[s], transversal axons of the basket cells which course transversely in the molecular layer of the cerebellar cortex just above the Purkinje cell bodies and which give off branches that synapse with the Purkinje cells.

fiber[s], tunnel terminal portions of cochlear nerve fibers as they cross the tunnel of Corti to end on the hair cells of the organ of Corti.

fiber[s], ventral superficial arcuate fibers that arise in the arcuate nucleus, adjacent to the pyramid in the medulla oblongata. The fibers pass dorsolaterally on the surface of the medulla to enter the inferior cerebellar peduncle and terminate in the cerebellum.

fiber[s] of Wallenberg‑Kilmoff fibers of the flocculooculomotor tract.

fibrae ansatae fiber bundle connecting the area in front of the lamina terminalis and the tuber cinereum.

field, frontal eye area of the frontal lobe cortex concerned with voluntary eye movements. see : Brodmann's area 8.

field, H, of Forel see field, prerubral.

field, H₁, of Forel see fasciculus, thalamic.

field, H₂, of Forel see fasciculus, lenticular.

field, occipital eye area of the occipital lobe cortex associated

with automatic [following] eye movements: Brodmann's areas 18 and 19.

field, prerubral area just rostral to the red nucleus, and containing rubrothalamic and dentothalamic fibers, Syn: H field of Forel; tegmental field of Forel.

field, tegmental, of Forel see field, prerubral.

field, triangular, of Gombault and Philippe sacral portion of the septomarginal fasciculus.

field, visual area seen by one or both eyes,

field of Wernicke planum temporale.

fila plural of filum.

fillet, lateral see lemniscus, lateral.

fillet, median see lemniscus, medial.

filum[a], olfactory delicate fascicles of olfactory nerve fibers which arise from specialized olfactory cells in the upper part of the nasal mucosa, pass through openings in the cribriform plate and end in the olfactory bulb.

filum terminale [N.A.] threadlike filament of pia mater extending caudally from the caudal tip of the spinal cord through the subarachnoid space, acquiring arachnoid and dural investments, and attaching to the dorsal surface of coccyx.

filum terminale externum that part of the filum terminale outside the subarachnoid space and having arachnoid and dural investments. Syn: coccygeal ligament.

filum terminale internum that part of the filum terminale within the subarachnoid space.

fimbria [L. fringe] bundle of nerve fibers arising from cells in the cornu ammonis, extending posteriorly along the hippocampus and continuing as the fornix.

fissura prima see fissure, primary.

fissure [L. fissura—cleft or slit] see also sulcus.

fissure, calcarine deep fissure extending across the medial surface of the occipital lobe and slightly onto the lateral surface.

fissure, central see sulcus, central.

fissure, choroid 1. fissure located between the upper surface of the thalamus and the lateral edge of the fornix in the body of the lateral ventricle, and between the stria terminalis and the edge of the fimbria in the inferior horn. The choroid plexus of the lateral ventricle is attached along the edges of the choroid fissure and projects into the ventricle, 2. fissure extending along the ventral surface of the optic stalk and optic cup of the developing eye and optic nerve. Through this fissure branches of the ophthalmic artery and vein communicate with the interior of the eyeball.

fissure, collateral fissure on the inferior surface of the cerebrum between the parahippocampal gyrus and the occipitotemporal gyrus.

fissure fimbriodentate fissure on the medial surface of the temporal lobe between the fimbria and the dentate gyrus.

fissure, great horizontal fissure which approximately separates the superior from the inferior half of the cerebellum. Specifically, it separates the folium vermis and the posterior superior lobules above it, from the tuber and the posterior inferior lobules below it.

fissure, hippocampal fissure on the medial surface of the temporal lobe, dorsomedial to the parahippocampal gyrus between the dentate gyrus and the subiculum.

fissure, horizontal cerebellar see fissure, great horizontal

fissure, interhemispheric deep vertical fissure between the two cerebral hemispheres. Syn: longitudinal fissure.

fissure, interlobar any fissure which serves as a boundary between lobes.

fissure, intralobar any fissure contained within the boundaries of a lobe.

fissure, lateral horizontally placed fissure on the lateral surface of the cerebrum separating the temporal lobe from the parietal and frontal lobes. Syn: fissure of Sylvius.

fissure, longitudinal see fissure, interhemispheric.

fit, uncinate disorder characterized by olfactory hallucinations, usually of an unpleasant nature.

fissure, lunate half‑moon shaped indentation capping the tip of the calcarine fissure on the lateral surface of the brain, present in some subhuman primate brains and sometimes in man. Syn: simian fissure.

fissure, parietooccipital deep fissure on the medial surface of the cerebrum, between the occipital and parietal lobes and extending from the dorsal surface to the calcarine fissure just posterior to the corpus callosum. Syn: occipitoparietal sulcus. fissure, postcentral. 1. see sulcus, postcentral [of the cerebral hemisphere]. 2. fissure on the superior surface of the cerebellum, separating the central and ala centralis portions anteriorly from the culmen and anterior crescentic lobules posteriorly.

fissure, postclival fissure on the superior surface of the cerebellum between the clivus and the posterior crescentic lobules anteriorly and the folium vermis and the posterior superior lobules posteriorly. It separates the lobulus simplex from the remainder of the posterior lobe [of Larsell].

fissure, posterolateral lateral extension of the postnodular fissure of the cerebellum between the flocculus anteriorly and the tonsil and biventer posteriorly.

fissure, postnodular fissure on the anterior, inferior surface of the vermis between the nodule anteriorly and the uvula posteriorly.

fissure, postpyramidal fissure on the inferior surface of the cerebellum between the pyramis and biventers anteriorly and the tuber and the posterior inferior [and gracile] lobules posteriorly.

fissure, precentral 1. see sulcus, precentral [of the cerebral hemisphere]. 2. Fissure on the superior surface of the cerebellum between the lingula and the central lobule of the cerebellar vermis.

fissure, preclival fissure on the superior surface of the cerebellum between the culmen and the anterior crescentic lobules anteriorly and the clivus and the posterior crescentic lobules posteriorly. It separates the anterior and posterior lobes [of Larsell]. It is the first fissure to appear in the corpus cerebelli, but not the first fissure in the cerebellum. Syn: primary sulcus; fissura prima.

fissure, prepyramidal fissure on the inferior surface of the cerebellum between the uvula and tonsils anteriorly and the pyramis and biventers posteriorly.

fissure, primary preclival fissure of the cerebellum, which is the second, not the first cerebellar fissure to develop. Syn: fissura prima.

fissure of Rolando see sulcus, central, 1.

fissure, simian see fissure, lunate.

fissure, superior orbital opening between the greater and lesser wings of the sphenoid bone, through which the oculornotor, trochlear, and abducens nerves, the ophthalmic branch of the trigeminal nerve, and the ophthalamic vein pass.

fissure of Sylvius see fissure, lateral.

fissure, total any cerebral fissure deep enough that the tissue beneath it forms an eminence on the ventricular wall.

fissure, transverse cerebral fissure separating the occipital lobes and the cerebellum, in which the tentorium cerebelli is located. It continues forward between the splenium of the corpus callosum and the roof of the third ventricle.

fissure, ventral median see sulcus, ventral median.

Flack's node sinoatrial node.

Flechsig, Paul Emile [1847‑1929] Bohemian neurologist and professor of psychiatry in Leipzig, noted for his studies of central nervous system tracts and for his observations on myelination in the fetus. see area [oval]; tract; and loop of Flechsig.

fleece of Stilling network of fibers that surround the dentate nucleus.

flexure, cephalic ventral flexure of the embryonic brain at the junction of the forebrain and midbrain.

flexure, cervical ventral flexure of the embryonic central nervous system, at the junction of the brain and spinal cord.

flexure, mesencephalic, see flexure., cephalic.

flexure, pontine dorsal flexure of the embryonic metencephalon.

flocculus most caudal subdivision of the cerebellar hemisphere. It is a small projection on the anterior surface of the cerebellum, just lateral to the attachment of the acoustic nerve at the pontomedullary junction.

fluid, cerebrospinal clear, colorless liquid secreted by the choroid plexus of the lateral, third, and fourth ventricles, and contained within the ventricular system of the brain and spinal cord and within the subarachnoid space. Syn: liquor cerebrospinalis.

fluid, otic see endolymph.

fluid, periotic see perilymph.

fluid, Scarpa’s see endolymph.

fold, neural each lateral wall of the neural groove.

folium narrow, leaf-like fold of the cerebellar surface.

folium vermis subdivision of the cerebellar vermis between the clivus and the tuber.

Fontana, A. F. [1732‑1805] Italian anatomist. see space[s] of Fontana.

foot, end see neuropodium.

foot, perivascular extension of an astrocyte, which is applied to the surface of a blood vessel within the central nervous system.

foramen caecum [L. foramen—opening; from forare —to bore] small depression at the upper end of the ventral median sulcus on the ventral surface of the brainstem, between the two pyramids and just below the pons.

foramen, hypoglossal see canal, hypoglossal.

foramen, interventricular opening between the third ventricle and each lateral ventricle; Syn: foramen of Monro.

foramen, Jacobson's opening in the temporal bone, in the ridge between the jugular bulb and the carotid canal. through which the tympanic branch of the glossopharyngeal nerve [Jacobson's nerve] enters the tympanic cavity.

foramen, jugular opening in the base of the skull between the occipital and temporal bones, through the medial portion of which the glossopharyngeal, vagal, and accessory nerves pass, and through the lateral portion of which the sigmoid sinus empties into the internal jugular vein.

foramen of Key and Retzius see aperture, lateral, of the fourth ventricle.

foramen of Luschka see aperture, lateral, of the fourth ventricle.

foramen of Magendie see aperture, median of the fourth ventricle.

foramen magnum opening in the base of the skull through which the spinal cord is continuous with the brain, and through which also pass the spinal accessory nerves, and the vertebral arteries and veins.

foramen of Monro see foramen, interventricular.

foramen [ina] nervosum[a] series of small radial slits along the tympanic lip of limbus laminae spiralis, through which small fascicles of cochlear nerve fibers emerge to enter the organ of Corti.

foramen [ina], olfactory small openings in the cribriform plate of the ethmoid bone in the floor of the cranial cavity through which the olfactory nerve fibers pass.

foramen, optic opening in the sphenoid bone at the back of the orbit through which the optic nerve and ophthalmic artery pass. Syn: optic canal.

foramen ovale opening in the base of the skull through which passes the mandibular division of the trigeminal nerve.

foramen rotundum opening in the base of the skull through which passes the maxillary division of the trigeminal nerve.

foramen spinosum opening in the base of the skull through which the middle meningeal artery enters the cranial cavity.

foramen, stylomastoid opening in the temporal bone, just behind the styloid process. through which the facial nerve emerges from the skull,

foramina plural of foramen.

forceps, anterior fibers of the corpus callosum which extend forward into the frontal lobe. Syn: forceps minor; frontal radiation.

forceps major see forceps, posterior.

forces minor see forceps, anterior.

forceps, posterior fibers of the corpus callosum which extend posteriorly into the occipital lobe. Syn: forceps major; occipital radiation.

forebrain cerebrum and diencephalon see also prosencephalon.

Forel, A. C. [1848‑1931] Swiss neurologist. For commissure of Forel, see decussation, supramammillary; for decussation of Forel, see decussation, ventral tegmental; for H, H₁, and H₂ fields of Forel, see, respectively, field, prerubral; fasciculus, thalamic; and fasciculus, lenticular.

formatio reticularis [N.A.] see formation, reticular.

formation, Ammon's see formation, hippocampal; hippocampus.

formation, hippocampal complex of hippocampus or cornu ammonis, dentate gyrus, and subiculum. see also cornu ammonis; hippocampus.

formation, reticular area in the tegmentum of the midbrain and pons and its continuation into the medulla and upper spinal cord, consisting of small groups of nerve cells interspersed among horizontally and vertically running nerve fibers, and excluding the cranial nerve nuclei and roots and the long fiber tracts. Syn: formatio reticularis.

fornix bundle of fibers continuous with the fimbria and which arches from the hippocampus upward and medially [posterior pillar], almost to meet its counterpart from the other side, then passes forward and downward in the free edge of the septum pellucidum [body] and turns backward and downward [anterior pillar] into the hypothalamus to end mainly in the mammillary body.

fornix, body main mass of fornix fibers extending forward along the lower border of the septum pellucidum, from the hippocampal commissure to a point just above the anterior commissure.

fornix dorsalis fibers from the induseum griseum or perhaps the cingulate gyrus, which cut through the corpus callosum and join the fornix.

fornix periphericus see cingulum.

fornix, postcommissural see pillar, anterior, for the fornix.

fornix, precommissural fornix fibers which pass anterior to the anterior . commissure.

fornix, subcallosal see fornix, body.

fornix, superior white stripe of Lancisi.

fossa, anterior cranial [L. fossa‑ditch] depression on the floor of the cranial cavity, above the orbit and containing the frontal lobes of the cerebrum.

fossa, intercrural see fossa, interpeduncular.

fossa, interpeduncular space on the anterior surface of the midbrain between the bases of the two cerebral peduncles. Syn: fossa of Tarini; intercrural fossa.

fossa, middle cranial depression on the floor of the cranial cavity, posterior to the greater wing of the sphenoid bone, and containing the temporal lobes of the cerebrum.

fossa, olfactory depression in the anterior fossa of the cranial cavity, on either side of the crista galli. Its floor is the cribriform plate and it contains the olfactory bulb.

fossa, posterior cranial that part of the cranial cavity caudal to the tentoriurn cerebelli, and containing the pons, medulla, and cerebellum.

fossa, rhomboid floor of the fourth ventricle.

fossa, Sylvian depression on the lateral surface of the developing cerebral hemisphere in the area destined to become the insula, covered by the opercula of the lateral fissure,

fossa of Tarini see fossa, interpeduncular.

fovea centralis slight depression in the center of the macula lutea of the retina, containing only cones and no rods, and constituting the area of keenest vision.

fovea, inferior shallow, angular depression in the sulcus limitans in the medullar portion of the rhomboid fossa at the junction of the vestibular area and the hypoglossal and vagal trigones.

fovea, superior shallow, angular depression in the sulcus limitans between the facial colliculus and the vestibular area in the pontine portion of the rhomboid fossa.

Frankenhauser’s ganglion see ganglion, Frankenhauser’s.

frenulum veli narrow midline band extending from the anterior medullary velum into the tectum between the two inferior colliculi.

Friedreich, Nikolaus [1825‑1882] German neurologist of Würzburg and Heidelberg. In 1875 he described a familial type of ataxia with an associated loss of sense of position [Friedreich's ataxia].

frontal [L. frons—forehead] pertaining to the frontal lobe or its cortex.

Froriep, August von [1849‑1917] German anatomist. see ganglion, Froriep’s.

-fugal suffix denoting efferent conduction from the region indicated.

fundus oculi retinal surface of the eyeball, seen through the pupil.

funiculus [L. little cord] one of the large subdivisions of white matter set off by the dorsal and ventr4l horns of the spinal cord gray matter.

funiculus, anterior see funiculus, ventral.

funiculus cuneatus see fasciculus cuneatus.

funiculus, dorsal spinal cord white matter between the dorsal horn and dorsal median septum. Syn: posterior column; posterior funiculus.

funiculus gracilis see fasciculus gracilis.

funiculus, lateral white matter on either side of the spinal cord, between the dorsal and the ventral horns.

funiculus, posterior see funiculus, dorsal.

funiculus separans ridge of thickened ependyma between the vagal trigone and the area postrema, in the caudal part of the rhomboid fossa.

funiculus, ventral spinal cord white matter between the ventral horn and the ventral median sulcus. Syn: anterior funiculus.

fusimotor pertaining to the gamma motor neurons which innervate the intrafusal muscle fibers of a muscle spindle to control the gain on neuromuscular stretch receptors.

g

GABA see gamma-aminobutyric acid.

Gabelzellen large, modified pyramidal cells of the auditory cortex, They have a broad base and relatively short vertical diameter.

Galen, Claudius [AD 131‑201] Roman physician, the leading medical authority of the Christian world for 1400 years. He described many parts of the brain. See veins, great and lesser, of Galen.

gamma‑aminobutyric acid [GABA] neurotransmitter which may have an inhibitory function in the central nervous system.

gamma efferent see fibers, gamma efferent. see also loop, gamma; fusimotor.

ganglia, basal subcortical masses of gray matter of the cerebrum, namely, the caudate nucleus, putamen, globus pallidus, amygdala, and claustrum. Syn: basal nuclei.

ganglia central thalamus and basal ganglia.

ganglion [Gr. swelling] 1. group of nerve cell bodies located outside the central nervous system. 2. old term for any group of nerve cells.

ganglion of Andersch inferior [petrosal ganglion of the glossopharyngeal nerve.

ganglion, aorticorenal collateral ganglion near the origin of each renal artery. It receives preganglionic sympathetic fibers, mostly from the least splanchnic nerve, and sends postganglionic fibers to the kidney and adjoining structures.

ganglion, Arnold's see ganglion, otic.

ganglion, Auerbach's parasympathetic ganglion cells in the myenteric plexus.

ganglion, auricular see ganglion, otic.

ganglion, basal see ganglia, basal.

ganglion of Bochdalek thickening in the superior dental plexus at the junction of the anterior and middle alveolar nerves, and which is not a true ganglion since it consists of interlacing bundles of nerve fibers and contains no nerve cells.

ganglion, Boettcher's small ganglionic mass on the vestibular nerve.

ganglion, cardiac small parasympathetic ganglion in the superficial cardiac plexus below the arch of the aorta. It receives preganglionic fibers from the left inferior cardiac branch of the vagus nerve. Syn: ganglion of Wrisberg.

ganglion, celiac relatively large collateral ganglion in the celiac plexus on either side of the celiac artery. It receives preganglionic sympathetic fibers from the thoracic splanchnic nerves and sends postganglionic fibers to the stomach, duodenum, liver, spleen, and pancreas. Syn: ganglion solare.

ganglion cell see cell, ganglion.

ganglion, cervicodorsal see ganglion, stellate.

ganglion, cervicothoracic see ganglion, stellate.

ganglion, chain ganglion of the sympathetic trunk, containing cell bodies of the postganglionic sympathetic fibers to visceral structures at the periphery of the body. in the head and in the thorax. Syn: paravertebral ganglion.

ganglion, ciliary parasympathetic ganglion of the oculornotor nerve, from which postganglionic fibers supply the ciliary muscle and the constrictor iridi of the eye.

ganglion, coccygeal unpaired sympathetic ganglion located in the pelvis at the junction of the two sympathetic trunks anterior to the coccyx. Syn: ganglion impar.

ganglion, collateral sympathetic ganglion located near the origin of one of the major abdominal arteries, supplying postganglionic sympathetic fibers to organs of the abdomen and pelvis. Syn: prevertebral ganglion.

ganglion of Corti see ganglion, spiral.

ganglion, dorsal root ganglion on the dorsal root of spinal nerves, containing cells or origin for sensory neurons of spinal nerves. Syn: spinal ganglion.

ganglion of Ehrenritter superior petrosal ganglion of the glossopharyngeal nerve.

ganglion, episcleral parasympathetic ganglion of the oculomotor nerve, located on the sclera of each eye. It receives preganglionic fibers from the Edinger-Westphal nucleus and sends postganglionic fibers to the constrictor muscle of the iris, and is said to be concerned with pupillary constriction in accommodation.

ganglion, Frankenhauser's parasympathetic ganglion cells in terminal ganglia of the uterovaginal plexus.

ganglion, Froriep's small ganglion on the hypoglossal nerve, present in the embryo but absent in the adult.

ganglion, Gasserian see ganglion, semilunar; ganglion, trigeminal.

ganglion, geniculate sensory ganglion of the facial nerve, located at the bend of the facial canal in the petrous portion of the temporal bone.

ganglion, habenular see habenula.

ganglion impar see ganglion, coccygeal.

ganglion, inferior 1. petrosal ganglion of the glossopharyngeal nerve. 2. Nodose ganglion of the vagus nerve.

ganglion, inferior mesenteric collateral ganglion near the origin of the inferior mesenteric artery. It receives preganglionic fibers from the lumbar splanchnic nerves and sends postganglionic fibers to the descending and the sigmoid colon and pelvic organs.

ganglion, jugular somatic sensory ganglion of the vagus nerve. Syn: superior ganglion of the vagus nerve.

ganglion, Langley's parasympathetic ganglion of the facial nerve, located at the hilus of the submandibular gland and from which postganglionic fibers supply the submandibular gland.

ganglion, Laumonier’s carotid ganglion.

ganglion, Ludwig’s ganglion associated with the cardiac plexus.

ganglion, Meckel’s see ganglion, pterygopalatine.

ganglion of Meynert see substantia innominata.

ganglion, nodose visceral sensory ganglion of the vagus nerve. Syn: inferior ganglion of the vagus nerve.

ganglion, otic parasympathetic ganglion which receives preganglionic fibers from the glossopharyngeal nerve and from which postganglionic fibers supply the parotid gland. Syn: Arnold's ganglion; auricular ganglion.

ganglion, paravertebral see ganglion, chain.

ganglion, petrosal visceral sensory ganglion of the glossopharyngeal nerve. It is located in a notch at the lower border of the jugular foramen, Syn: inferior ganglion of the glossopharyngeal nerve; petrous ganglion.

ganglion, petrous see ganglion, petrosal.

ganglion, prevertebral see ganglion, collateral.

ganglion, pterygopalatine parasympathetic ganglion of the facial nerve, from which postganglionic fibers supply the lacrimal, nasal, and palatine glands. Syn: sphenopalatine ganglion.

ganglion, Remak’s clusters of parasympathetic ganglion cells on the heart wall.

ganglion renal see ganglion, aorticorenal.

ganglion, Ribe’s tiny sympathetic ganglion sometimes occurring on the anterior communicating artery.

ganglion, Scarpa’s see ganglion, vestibular

ganglion, semilunar sensory ganglion of the trigeminal nerve, Syn; Gasserian ganglion; trigeminal ganglion.

ganglion solare see ganglion, celiac.

ganglion, sphenopalatine see ganglion, pterygopalatine.

ganglion, spinal see ganglion, dorsal root.

ganglion, spiral sensory ganglion of the cochlear nerve, located in the cochlea and composed of bipolar cell bodies. Syn: ganglion of Corti.

ganglion, stellate fused inferior cervical and first thoracic and occasionally second thoracic ganglia of the sympathetic trunk, or the inferior cervical ganglion alone. Syn: cervicodorsal ganglion; cervicothoracic ganglion.

ganglion, submandibular parasympathetic ganglion of the facial nerve, from which postganglionic fibers supply the sublingual glands. Syn: submaxillary ganglion.

ganglion, submaxillary see ganglion, submandibular.

ganglion, superior 1. see ganglion, superior petrosal. 2. see ganglion, jugular.

ganglion, superior cervical uppermost ganglion of the sympathetic chain from which postganglionic fibers are distributed to the dilator muscle of the pupil, the smooth muscle of the upper eyelid, the lacrimal and salivary glands, and the sweat glands, cutaneous blood vessels, and smooth muscle of the hair follicles of the face, neck, and upper shoulder. It also supplies the heart.

ganglion, superior mesenteric collateral ganglion near the origin of the superior mesenteric artery. It receives preganglionic fibers mostly from the greater splanchnic nerves and sends postganglionic fibers to the small intestine, and to the ascending and the transverse colon.

ganglion, superior petrosal somatic sensory ganglion of the glossopharyngeal nerve. Syn: superior ganglion of the glossopharyngeal nerve.

ganglion, terminal any parasympathetic ganglion located in or near the organ innervated.

ganglion, trigeminal see ganglion, semilunar.

ganglion of Valentin thickening in the superior dental plexus, above the root of the second premolar tooth at the junction of the middle and posterior superior alveolar nerves, and which is not a true ganglion since it consists of interlacing bundles of nerve fibers and contains no nerve cells.

ganglion, vertebral small sympathetic ganglion on or near the vertebral artery as it begins its ascent through the foramina of the cervical vertebrae. Usually regarded as a detached part of the middle cervical or stellate ganglion, it supplies postganglionic fibers for the vertebral artery and its branches.

ganglion, vestibular sensory ganglion containing bipolar cell bodies of the vestibular nerve and consisting of superior and inferior portions, located in the internal auditory meatus of the temporal bone. Syn: Scarpa's ganglion.

ganglion of Wrisberg see ganglion, cardiac.

ganglionic 1. pertaining to the cell bodies of neurons. 2. pertaining to sensory or autonomic ganglia of the peripheral nervous system.

Ganser, commissure of see decussation, dorsal supraoptic.

Gasser, Johann Laurentius [1723‑1765] Austrian anatomist for whom the sensory ganglion of the trigeminal nerve was named..

gemmule[s] short, spiny processes on the dendritic branches of some [or all] neurons within the central nervous system, including Purkinje cells and pyramidal cells of the cerebral cortex. Syn: dendritic spines.

general somatic afferent [GSA] pertaining to the nerve component consisting of fibers which conduct impulses to the central nervous system from muscles, tendons and joints [proprioceptive] and from somatic structures related to the skin, i.e. pain, temperature, and touch [exteroceptive.

general somatic efferent [GSE] pertaining to the nerve component consisting of fibers which conduct impulses from motor nuclei of the spinal cord to striated muscle of somatic origin.

general visceral afferent [GVA] pertaining to the nerve component consisting of fibers which conduct impulses to the central nervous system from structures derived from entoderm and splanchnic mesoderm, including thoracic, abdominal, pelvic, and certain head viscera but excluding the fibers carrying taste and smell.

general visceral efferent [GVE] pertaining to the nerve component consisting of fibers which supply the motor innervation of smooth muscle, cardiac muscle, and glands, and comprising the pre‑ and postganglionic fibers of the autonomic nervous system.

geniculate [L. geniculare—to bend the knee] see ganglion, geniculate; body and nucleus, lateral and medial geniculate.

geniculum point at which the facial nerve bends sharply backward in the facial canal. Syn: external genu of VIL

Gennari, Francesco [1750‑1796?] Italian physician who recognized the conspicuous stripe in the occipital lobe cortex as early as 1776 and described it in 1782.

Genu [L. knee]see also knee.

genu of the corpus callosum anterior portion of the corpus callosum; see also rostrum, body, splenium.

genu, external of the facial nerve sharp bend made by the facial nerve within the facial canal in the petrous bone.

genu of the Internal capsule that part of the internal capsule between the posterior part of the head of the caudate nucleus and anterior part of the thalamus medially and the lentiform nucleus laterally.

genu, internal of the facial nerve loop of the motor root of the facial nerve over the rostral end of the abducens nucleus in the pons,

Giacomini’s band see band, Giacomini's.

Glerke, H. P. [1847‑1886] German anatomist. Gierke's respiratory bundle is fasciculus solitarius.

gitter cell see cell, gitter.

gland, pineal see body, pineal.

glaucoma disorder characterized by excessive intraocular pressure.

glia [Gr. glue] a contraction used as a synonym for neuroglia.

glia limitans membrane composed of footplates of astrocytes on the surface of blood vessels within the central nervous system [the perivascular glia limitans] and at the surface of the central nervous system [the external glia limitans].

globus pallidus [L. globus—ball or globe; pallidus—pale; medial portion of the lentiform nucleus between the internal capsule and the putamen. Fibers from this nucleus enter the ansa lenticularis, lenticular fasciculus, and other tracts associated with the extrapyramidal system. Syn: pallidum; paleostriatum.

glomerulus, cerebellar [L. glomerulus—little ball] see island, cerebellar.

glomerulus, olfactory spherical structure in the superficial part of the olfactory bulb. It is composed of the terminal portions of olfactory nerve axons and the terminal portions of mitral cell dendrites with which they synapse.

glomus choroideum [L. glomus—ball] [N.A.] expanded portion of the choroid plexus in the atrium of the lateral ventricle,

Golgi, Camillo [1843‑1926] Italian anatomist who introduced the silver chromate technique for nerve cells [18731. He described many features of silver‑stained material including the Golgi [reticular] apparatus [1898], Golgi type I and type II cells [1886], the Golgi tendon organ [neurotendinous spindle] [1880] and the Golgi‑Mazzoni corpuscle. Shared Nobel prize with Cajal.

Goll, Friedrich [1829‑1903] Swiss anatomist. He described fasciculus gracilis [column of Goll] in 1860. Nucleus gracilis is also called the nucleus of Goll.

Gombault, Francçois Alexis Albert [1844‑1904] French physician who described the. sacral portion of the septomarginal fasciculus, which was also described by Philippe and known as the triangle of Gombault‑Phillippe.

Gowers, Sir William Richard [1845‑1915] English physician who published notable descriptions of many neurologic disorders. He also described the ventral spinocerebellar tract [tract of Gowers] in 1880. He was one of the first to recognize the usefulness of the ophthalmoscope and to describe retinal findings in a number of diseases.

granulations, arachnoid clusters of arachnoid villi, located mainly in lacunae of the superior longitudinal sinus, through which cerebrospinal fluid enters the venous system.

granule[s], Nissl cytoplasmic bodies which contain RNA and iron. They are of varying size and are present in nerve cell bodies [exclusive of the axon hillock]. Syn: chromidial substance, tigroid bodies or granules.

granule[s], tigroid see granules, Nissl.

Gratiolet, Louis Pierre [1815‑1865] French anatomist and zoologist who described the optic radiation [Gratiolet's optic radiation]. see also convolutions of Gratiolet.

gray, central cellular area around the cerebral aqueduct [periaqueductal gray], or around the central canal, especially that of the closed medulla.

gray, deep tegmental see nucleus mesencephalicus profundus.

gray, dorsal funicular area of the dorsal horn of the spinal cord, ventral and ventromedial to substantia gelatinosa. It consists of some fairly large and other small cells and is present at all spinal cord levels. It contains cells of origin for a number of ascending tracts. Syn: nucleus proprius, nucleus of Waldeyer. See also Waldeyer layer.

gray, dorsal visceral subdivision of nucleus solitarius located just dorsomedial to fasciculus solitarius and best developed at the level of the entering glossopharyngeal nerve fibers. It is a receptive nucleus for incoming gustatory fibers of the facial, glossopharyngeal, and vagal nerves. From it secondary fibers cross the midline, join the medial lemniscus, and terminate partly in the dorsal thalamus. Syn: dorsal nucleus of fasciculus solitarius; gustatory nucleus.

gray, parahypoglossal see nucleus, parahypoglossal.

gray, parasolitary see nucleus parasolitarius.

gray, periaqueductal cellular area surrounding the cerebral aqueduct of the midbrain gray, perihypoglossal see nucleus, parahypoglossal.

gray, pontine cells intermingled with the bundles of nerve fibers in the base of the pons. Their axons constitute the fibers of the pontocerebellar tract.

gray, secondary visceral dorsal horn nucleus located just dorsal to the lateral horn in cord segments T_I‑L₃, for relay of impulses from the viscera to nearby visceral motor nuclei and, by way of a bilateral multisynaptic ascending neuron chain [secondary ascending visceral tract], to higher centers.

gray, sublenticular see gray, substriatal.

gray, subrubral tegmental gray of the midbrain, located ventral to the red nucleus.

gray, substriatal cellular area ventral to the lentiform nucleus, consisting of the substantia innominata medially and nucleus subputaminalis laterally. Syn: sublenticular gray.

gray, trapezoid cells associated with the trapezoid fibers in the ventral and caudal part of the pontine tegmentum. They receive fibers from the ventral cochlear nucleus and their axons [trapezoid fibers] enter the lateral lemniscus.

groove, neural groove formed by the buckling of the neural plate. When the neural folds on either side thicken and their dorsal portions fuse, the neural groove becomes the neural tube.

ground bundle see fasciculus proprius.

GSA see general somatic afferent.

GSE see general somatic efferent.

Gudden, Bernhard Alloys von [1824‑1886] German neurologist who described the most ventral of the supraoptic decussations [Gudden's commissure] in 1848. He also described retrograde degeneration of the thalamus after cortical lesions Gudden’s atrophy]. see also Gudden's tract; nucleus of Gudden.

gustatory pertaining to the sense of taste.

GVA see general visceral afferent.

GVE see general visceral efferent.

gyrencephalic having a convoluted cerebrum.

gyrus [Gr. gyros‑circle] elevation or ridge on the surface of the cerebrum, separated from other gyri by sulci or fissures. see also convolution.

gyrus, angular subdivision of the inferior parietal lobule, it caps the posterior tip of the, superior temporal sulcus just posterior to the supramarginal gyrus. Syn: Brodmann's area 39.

gyrus, anterior central see gyrus, precentral.

gyrus, anterior parolfactory anterior portion of the parolfactory area, between the anterior and posterior parolfactory sulci, on the medial surface of the frontal lobe.

gyrus brevis one of the short gyri of the insula, anterior to the central sulcus of the insula.

gyrus, callosomarginal see gyrus, cingulate.

gyrus, cingulate gyrus on the medial surface of the cerebrum which adjoins and overlies the corpus callosum from the subcallosal region into the temporal lobe. Syn: supracallosal gyrus; callosomarginal gyrus.

gyrus, dentate narrow, scalloped band of cortex along the dorsal margin of the hippocampal fissure, A subdivision of the hippocampal formation, in cross section it is characterized by closely packed, deeply staining nerve cells in a folded layer, the free margins of which interlock with the edge of the cornu ammonis. Syn: dentate fascia; fascia dentata; Tarin's fascia.

gyrus fasciolaris [N.A.] see fasciola cinerea.

gyrus, first temporal see gyrus, superior temporal.

gyrus, fornicate fornicate lobe. see cerebrum, lobes.

gyrus, fusiform gyrus on the inferior surface of the cerebrum between the collateral sulcus and parahippocampal gyrus medially and the inferior temporal sulcus and gyrus laterally. Syn: [medial] occipitotemporal gyrus.

gyrus, hippocampal see gyrus, parahippocampal.

gyrus, inferior frontal gyrus on the lateral surface of the frontal lobe between the inferior frontal sulcus and the lateral fissure, and anterior to the precentral sulcus. It is divided by the anterior horizontal and anterior ascending rami of the lateral fissure into opercular, triangular, and orbital portions. see also convolution, Broca's.

gyrus, inferior temporal gyrus between the middle temporal sulcus on the lateral surface of the temporal lobe and the inferior temporal sulcus on the ventral surface. Syn: lateral occipitotemporal gyrus; third temporal gyrus.

gyrus intralimbic semidetached posterior tip of the uncus of the temporal lobe.

gyrus, lateral occipital any of several irregular and variable gyri on the lateral surface of the occipital lobe, usually separated into a superior and an inferior group by the lateral occipital sulcus.

gyrus, lateral occipitotemporal see gyrus, inferior temporal.

gyrus, lateral olfactory narrow band of gray matter along the lateral olfactory stria. Syn: prepyriform area.

gyrus, lingual gyrus on the medial surface of the cerebrum, located below the calcarine fissure in the occipital lobe and extending forward into the temporal lobe medial to the collateral sulcus to become continuous with the parahippocampal gyrus. Syn: lingula.

gyrus, long see gyrus longus.

gyrus longus long gyrus of the insula, posterior to the central sulcus of the insula.

gyrus, medial occipitotemporal see gyrus, fusiform.

gyrus, medial olfactory narrow cellular area along the medial olfactory stria.

gyrus, middle frontal gyrus on the lateral surface of the frontal lobe between the superior and inferior frontal sulci, and anterior to the precentral sulcus.

gyrus, middle temporal gyrus on the lateral surface of the temporal lobe between the superior and middle temporal sulci. Syn: second temporal gyrus.

gyrus, occipitotemporal see gyrus, fusiform.

gyrus, olfactory either of the narrow bands of gray matter along the medial and lateral olfactory striae.

gyrus, orbital any of the gyri on the ventral [orbital] surface of the frontal lobe, lateral to the olfactory sulcus.

gyrus, paracentral cortical area on the medial surface of the cerebrum around the dorsomedial tip of the central sulcus and bounded by the paracentral sulcus anteriorly, the cingulate sulcus ventrally and the marginal sulcus posteriorly. Syn: paracentral lobule.

gyrus, parahippocampal gyrus on the medial surface of the temporal lobe of the cerebrum, although sometimes it is considered separately as a part of the limbic lobe. It is separated from the fusiform gyrus laterally through most of its length by the collateral sulcus and anteriorly by the rhinal sulcus. It is continuous posteriorly with the lingual gyrus. Syn: hippocampal gyrus.

gyrus paraterminalis [L; N.A.1] see area, paraterminal.

gyrus, postcentral gyrus on the lateral surface of the parietal lobe extending from the lateral fissure to the dorsal border of the hemisphere and located between the central and postcentral sulci. Syn: ascending parietal convolution; posterior ascending convolution: posterior central gyrus.

gyrus, posterior central see gyrus, postcentral.

gyrus, posterior parolfactory posterior portion of the parolfactory area between the posterior parolfactory sulcus and the lamina terminalis on the medial surface of the frontal lobe.

gyrus, precentral gyrus on the lateral surface of the frontal lobe extending from the lateral fissure to the dorsal border of the hemisphere and located between the central and precentral sulci. Syn: anterior ascending convolution; anterior central gyrus; ascending frontal convolution.

gyrus rectus [N.A.] gyrus on the ventral surface of the frontal lobe, medial to the olfactory sulcus and extending onto the medial surface of the hemisphere. Syn: straight gyrus,

gyrus, second temporal see gyrus, middle temporal.

gyrus, short see gyrus brevis.

gyrus, straight see gyrus rectus.

gyrus, subcallosal small gyrus immediately ventral to the genu and rostrum of the corpus callosum and continuous anteriorly with the cingulate gyrus. Syn: peduncle of the corpus callosum; Zuckerkandl’s convolution.

gyrus, subrostral narrow strip of cortex between the subcallosal gyrus and the overlying corpus callosum.

gyrus, superior frontal gyrus anterior to the precentral and paracentral sulci and between the superior frontal sulcus on the lateral surface of the frontal lobe and the cingulate sulcus on the medial surface.

gyrus, superior temporal gyrus on the lateral surface of the temporal lobe between the superior temporal sulcus and the lateral fissure. Syn: first temporal gyrus.

gyrus, supracallosal 1. see gyrus, cingulate. 2. see induseum griseum.

gyrus, supramarginal a subdivision of the inferior parietal lobule, it caps the posterior tip of the lateral fissure, between the postcentral and angular gyri. Syn: Brodmann's area 40.

gyrus, third temporal see gyrus, inferior temporal.

gyrus, transverse temporal either of two small gyri on the opercular surface of the temporal lobe, within the lateral fissure, and comprising the auditory cortex. Syn: Brodmann's areas 41 and 42; Heschl’s convolutions.

gyrus, triangular triangular portion of the inferior frontal gyrus, bounded by the anterior ascending and anterior horizontal rami of the lateral fissure, the lateral fissure proper and the inferior frontal sulcus. Syn: Brodmann's area 45.

gyrus, uncinate see uncus.

h

habenula /ha‑been’ u“‑la/ [L. habena —bridle rein or strap] small protuberance at the dorsal and posterior edge of the third ventricle, adjacent to the pineal body. It consists of a medial and a lateral habenular nucleus and is part of the epithalamus.

habenula perforata row of small openings, called foramina nervosa, along the tympanic lip of the limbus laminae spiralis.

Hall, Marshall [1790‑1857] English physiologist whose experiments on spinal cord reflexes established the difference between reflex and voluntary movement.

Haller, A. [1708‑1777] Swiss anatomist and physiologist for whom the commissure of Haller [commissura infima] and Haller’s layer [vascular layer of the choroid of the eye] were named.

Hammond, William Alexander [1828‑1900] athetosis [Hammond’s disease].

hamulus of the spiral lamina tip of the spiral lamina at the apical end of the cochlea.

Head, Sir Henry [1861‑1940] English neurologist who studied cutaneous innervation and the changes in sensibility following section of his own peripheral nerves. During and after World War I his work with brain‑injured soldiers greatly advanced knowledge of aphasia and related disorders.

Held, Hans [1866-1942] German anatomist. see bundle; calices; commissure; fibers; and end bulb of Held.

helicotrema /hel‑i‑co“‑tre“'ma/ [Gr. helix—coil; trema—hole] the opening at the apex of the cochlea whereby the scala vestibuli communicates with the scala tympani,

Helmholtz, Hermann von [1821‑1894] German physician, physiologist and physicist who invented the ophthalmoscope [1851] and contributed greatly to knowledge of neurophysiology, particularly in relation to vision and hearing. According to the Helmholtz theory of accommdation, the eye is adapted for near vision when, upon contraction of the ciliary muscle, the suspensory ligament of the lens is relaxed and the lens, because of its elasticity, becomes more globular.

Helweg, Hans Kristian Saxtorph [1847‑1901] Danish physician who described the olivospinal tract [Helweg’s tract]

hemianopsia, [hemianopia] blindness in one half of the visual field.

hemianopsia, [hemianopia], bitemporal blindness in the temporal visual field of each eye, after destruction of the crossing fibers in the optic chiasm.

hemianopsia [hemianopsia], homonymous blindness in the same half of the visual field for both eyes.

hemiparesis weakness of the two extremities on one side.

hemiplegia paralysis of one half of the body.

hemiplegia, alternate lower motor neuron paralysis of the muscles supplied by one cranial nerve‑and an upper motor neuron paralysis of the muscles of the opposite side of the body, resulting from a brain stem lesion on the side of the cranial nerve paralysis. Syn: alternate paralysis.

hemiplegia, crossed 1. paralysis of one upper extremity and the opposite lower extremity due to a lesion in the pyramidal decussation on the side of the upper extremity paralysis. Syn: crossed paralysis. 2. see hemiplegia, alternate.

hemisphere, cerebral cerebral cortex, its underlying white matter and the basal ganglia of one half the brain. see also cerebrum.

hemispherectomy removal of one cerebral hemisphere.

Henle, Friedrich Gustav Jacob [1809‑1885] German anatomist who made many contributions in the field of microscopic anatomy, including a description of the debate connective tissue sheath of peripheral nerve fibers [Henle’s sheath].

Herbst, Ernst Friedrich Gustav [1803‑1893] German anatomist who described a specialized encapsulated nerve ending [Herbst’s corpuscles] in the tissue around the bill and in the tongue of birds, in 1948.

Hering‑Breuer reflexes see reflex[es], Hering‑Breuer.

Hering’s nerve see nerve, Hering.

Herophilus [335‑280 BC] physician of Alexandria. The confluence of the sinuses is also called the torcular Herophili.

Heschl, Richard [1824‑1881] Austrian anatomist who described the transverse temporal gyri [Heschl's convolutions] in 1855.

Heubner’s artery see artery, recurrent.

hillock, axon see axon hillock.

hindbrain the medulla, pons and cerebellum. see also rhombencephalon.

hippocampus [Gr. sea horse] 1. eminence first observed by Achillini but named by Arantius. It projects into the inferior horn of the lateral ventricle and consists of the body y of the dentate gyrus, cornu ammonis, subiculum, and their associated nerve fibers. 2. sometimes this term is used with reference only to the cornu ammonis. see also formation, hippocampal.

hippocampus major see cornu ammonis.

hippocampus minor see calcar avis.

hippus condition or state of pupillary hyperexcitability.

Hirschsprung’s disease disorder involving megacolon resulting from the failure of neural crest cells to migrate and form the autonomic ganglia of the caudal part of the sastr6intestinal tract; congenital aganglionic megacolon.

His, Wilhelm [1831‑1904] Swiss anatomist noted for his studies on the embryologic development of the nervous system.

hook bundle see fasciculus, uncinate.

hormones, neurosecretory two neurohypophysial hormones [vasopressin and oxytocin] produced by cells of the supraoptic and paraventricular nuclei, respectively, and transported along fibers of the hypothalamohypophysial tract to the neurohypophysis.

horn, Ammon's see cornu ammonis.

horn, anterior 1. see horn, ventral. 2. subdivsion of the lateral ventricle, anterior to the interventricular foramen and bounded by the head of the caudate nucleus, corpus callosum, septum pellucidum, and fornix. Syn: frontal horn.

horn, descending, of the lateral ventricle see horn, inferior.

horn, dorsal posterior gray column of the spinal cord, as seen in spinal cord cross section and containing such cell groups as substantia gelatinosa, nucleus proprius, dorsal nucleus of Clarke, and secondary visceral gray. Syn: posterior horn.

horn, frontal see horn, anterior.

horn, inferior subdivision of the lateral ventricle within the temporal lobe and containing a portion of the choroid plexus. Syn: temporal or descending horn.

horn, intermediate see horn, lateral.

horn, lateral lateral gray column of the spinal cord as seen in sections of T_l‑L₃ cord segments and containing the intermediolateral nucleus.

horn, posterior 1. see horn, dorsal. 2. subdivision of the lateral ventricle projecting posteriorly into the occipital lobe.

horn, temporal see horn, inferior.

horn, ventral anterior gray column of the spinal cord, as seen in spinal cord cross section, and containing such cell groups as the ventromedial, dorsomedial, ventrolateral, dorsolateral, retrodorsolateral, accessory, central and sacral parasympathetic nuclei. Syn: anterior horn.

Horner, Johann Friedrich [1831‑1886] Swiss ophthalmologist who described the syndrome of unilateral ptosis, miosis, and anhidrosis of the face, neck and shoulder [Horner’s syndrome] in 1869.

Horsley, Sir Victor [1857‑1916] English surgeon and neurologist. His publications include contributions in several medical fields but he is known mainly as the father of neurosurgery.

humor, aqueous thin, watery fluid which fills the anterior and posterior chambers of the eye.

humor, vitreous see body, vitreous,

Huntington, George [1850‑1916] American physician who first described hereditary [Huntington’s] chorea, a fatal ailment.

hydrencephalocele abnormality in which the herniated brain forms a tumor in part composed of fluid.

hydrocephalus abnormal condition in which the skull and sometimes the brain are enlarged because of interference with the circulation or drainage of cerebrospinal fluid.

hydrocephalus, communicating hydrocephalus in which the openings between the ventricular spaces and between the fourth ventricle and subarachnoid space are patent.

hydrocephalus, internal see hydrocephalus, noncommunicating.

hydrocephalus, noncommunicating hydrocephalus in which there is obstruction of the flow of cerebrospinal fluid through the cerebral aqueduct or floor of the fourth ventricle to the subarachnoid space. Syn: internal hydrocephalus, obstructive

hydrocephalus, obstructive see hydrocephalus, noncommunicating.

hydromeningocele meninges abnormality in which a cystic tumor is caused by herniated meninges

hypercusis hypersensitivity to auditory stimuli, after injury to the stapedial branch of the facial nerve.

hypesthesia partial loss of sensation.

hypoglossal [Gr. hypo—under; glossa—tongue] and nucleus, see the nouns.

hypoglossus see nerve, hypoglossal.

hypokinesia reduction in the initiation, implementation, and facility of execution of movement.

hypothalamus subdivision of the diencephalon located on either side of the third ventricle, just ventral to the hypothalamic sulcus. It is important in the regulation of various visceral functions.

i

incisure, anterior cerebellar [L. incisura—a cutting into; from caedere—to cut] shallow indentation on the anterior margin of the superior surface of the cerebellum.

incisure, posterior cerebellar narrow indentation on the posterior and inferior surface of the cerebellum, containing the falx cerebelli.

incisure of Schmidt‑Lantermann funnel‑shaped structure within the myelin sheath of a peripheral nerve fiber. Syn: cleft of Schmidt‑Lantermann.

incisure of tentorium opening anterior to the tentorium cerebelli and enclosing the midbrain. Syn: tentorial notch.

induseum griseum [N.A.] thin layer of gray matter on the upper surface of the corpus callosum, continuous posteriorly with the dentate gyrus. Syn: hippocampal rudiment; supracallosal gyrus.

infratentorial caudal to the tentorium cerebelli, within the posterior fossa of the cranial cavity.

infundibulum [L .funnel] ventral evagination of the wall of third ventricle of the developing brain from which the neurohypophysis is derived.

insula [L. island] part of the cerebral cortex overlying the putamen and claustrum and forming the floor of the lateral fissure. Syn: island; island of Reil, isle of Teil, central lobe.

insular pertaining to the insula or its cortex.

interbrain see diencephalon.

intercalated [L. intercalare—to insert] neuron, internuncial.

internal capsule see capsule, internal.

interneuron see neuron, internuncial.

internode segment of a nerve fiber between two nodes of Ranvier.

internuncial [L. inter—between; nuncius—messenger] placed between, serving as a connecting link. see neuron, internuncial.

interoception visceral sensibility.

interolivary between the two inferior olivary nuclei.

interpeduncular between the bases of the two cerebral peduncles; a nucleus involved in involuntary motor behavior.

interthalamic connexus see massa intermedia.

intima pia see pia mater.

intraaxial inside the brain.

intracranial within the cranial cavity.

intrafusal pertaining to the small muscle fibers within a neuromuscular spindle.

intramedullary within the central nervous system.

intrathecal within a sheath; in relation to the nervous system, within the spinal subarachnoid space.

intumescence, cervical cervical enlargement of the spinal cord.

intumescence, lumbar lumbar enlargement of the spinal cord.

involuntary nervous system see system, autonomic nervous.

island see insula.

island, cerebellar cell‑free area bounded by granule cells in the granular layer of the cerebellar cortex. It contains mossy fiber and Golgi cell axons and granule cell dendrites which form complex synapses. Astroglial processes are also present.

island, plasma see island, cerebellar.

island of Reil see insula.

isle of Teil see insula.

isocortex see cortex, homogenetic.

isthmus of the fornicate gyrus extension of the cingulate gyrus into the temporal lobe between the splenium of the corpus callosum and the lingual gyrus.

isthmus of the pons that part of the pons rostral to the attachments of the cerebellar peduncles.

isthmus, temporal zone between the lateral ventricle and the posterior part of the insula and containing the temporal loop of the optic radiation, the corticotectal tracts, the auditory radiation, and other fiber bundles.

iter [L. a way or street] see aqueduct, cerebral.

j

Jackson, John Hughlings [1835‑1911] English physician noted for his pioneering work in neurology. He published many now classic reports on epilepsy and many other neurologic disorders as well as on the structure and function of the nervous system.

Jacobson, Ludwig Levin [1783‑1843] Danish anatomist who described the tympanic branch of the glossopharyngeal nerve [Jacobson Is nerve] and the tympanic-plexus [Jacobson's plexus] in 1818. The vomeronasal organ [Jacobson's organ] was reported in 1809. The vomeronasal nerve also is called Jacobson’s nerve.

jerk see reflex.

jugular [L. jugulum—throat] pertaining to the jugular veins.

juxtarestiform body see body, juxtarestiform.

k

Kaes or Kaes‑Bechterew, stripe of see stripe of Kaes.

Keith, A. [1866‑1955] London anatomist. The node of Keith and Flack is the sinoatrial node.

kernicterus /ka“rn-ik’terus/ [Gr. kern—kernel, nucleus; ikteros—jaundice; pathologic condition in which certain regions of the central nervous system are stained yellow with bile pigments, particularly the subthalamic nucleus, hippocampus, and globus pallidus.

Kernig, Vladimir Michailovich [1840‑1917] Russian neurologist who described a sign [Kernig’s sign] indicative of meningitis in 1884.

Kernohan notch indentation and necrosis of the brain due to pressure of the brain against the free edge of the tentorium cerebelli, often associated with tentorial herniation.

Key, Ernst Axel Henrik [1832‑1901] Swedish physician who, with G. M. Retzius described the lateral apertures of the fourth ventricle [foramina of Key and Retzius] and several neuroanatomical structures. see also sheath, Henle’s.

kinocilium single protoplasmic filament in each hair process of the hair cells in the cupula of the crista ampullaris of each semicircular duct. Bending of the kinocilia stimulates the sensory nerve fibers when the deflection is toward the utricle in the horizontal duct and away from the utricle in the vertical ducts [Lowenstein and Wersall, 1959].

Klimoff‑Wallenberg fibers see tract, flocculooculomotor.

knee, anterior, of the optic chiasm optic nerve fibers from the inferior media] quadrant of each retina which deviate into the contralateral optic nerve as they cross through the optic chiasm to enter the opposite optic tract.

knee jerk see reflex, patellar.

knee, posterior of the optic chiasm optic nerve fibers from the superior media] quadrant of each retina which deviate into the homolateral optic tract before they cross in the optic chiasm to enter the contralateral optic tract.

Koch’s node see node, sinoatrial.

koniocortex [Gr. konis—dust; L. corte—bark, rind] cortex of a sensory projection area, in which the granular layers predominate.

koniocortex, auditory Brodmann's area 41 [area AI].

Krause, Wilhelm Johann Friedrich [1833‑1910] German anatomist who described the end bulbs [of Krause] in 1860. see also fasciculus solitarius; ventricle, terminal.

l

L‑DOPA abbreviation for L-dihyroxyphenylalanine, a precursor of dopamine.

Labbé, Leon [1832‑1916] French surgeon. see vein of Labbé.

labyrinth, bony space within the petrous part of the temporal bone. which contains the various portions of the internal ear. Syn: osseous labyrinth.

labyrinth, endolymphatic see labyrinth, membranous.

labyrinth, membranous system of epithelial ducts and chambers of the internal ear which contain endolymph and are suspended within the periotic space of the bony labyrinth. It comprises the cochlear duct, saccule, utricle, three semicircular ducts and their connecting channels. Syn: otic labyrinth.

labyrinth, osseous see labyrinth, bony.

labyrinth, otic see labyrinth,. membranous.

labyrinth, periotic space containing perilymph, located between the membranous labyrinth of the internal ear and the epithelial lining of the bony labyrinth. Syn: periotic: space.

lagena see cecum, cupular.

lakes, lateral, of Trolard lacunae extending outward from the superior longitudinal sinus.

lamina [L. plate or layer] see also layer; stratum.

lamina, accessory medullary layer of nerve fibers partially subdividing the inner segment of the globus pallidus.

lamina, affixa ependymal epithelium covering the dorsal surface of the thalamus between the attachment of the choroid plexus medially and the stria terminalis laterally and forming part of the floor of the body of the lateral ventricle.

lamina basalis see membrane, basilar.

lamina[e] of the cerebral cortex see cortex, cerebral.

lamina cribrosa 1. perforated part of the sclera through which the optic nerve fibers pass as they leave the retina. 2. see plate, cribriform, 1.

lamina dysfibrosa layer II [Vogt] of the cerebral cortex.

lamina, external medullary 1. layer of medullated nerve fibers between the putamen and globus pallidus. 2. layer of medullated nerve fibers in the dorsal thalamus which separates the ventral and lateral nuclear groups on the medial side from the reticular nucleus laterally, and which is continuous ventrally with the thalamic fasciculus.

lamina infrastriata layer VI [Vogt] of the cerebral cortex.

lamina, internal medullary 1. layer of medullated nerve fibers between the inner and outer segments of the globus pallidus. 2. layer of medullated nerve fibers in the dorsal thalamus which separates the medial nucleus on the medial side from the ventral and lateral nuclear groups laterally and through which the mammillothalamic tract passes to reach the anterior nucleus of the dorsal thalamus.

lamina limitans anterior [N.A.] see membrane, Bowman's.

lamina limitans posterior [N.A.] see membrane, Descemet's.

lamina, membranous spiral see membrane, basilar.

lamina multiformis layer VI [Brodmann] of the cerebral cortex.

lamina, osseous spiral bony ridge which spirals around the modiolus of the cochlea and to which the basilar membrane is attached. lamina quadrigemina see tectum.

lamina rostralis membrane extending from the rostrum of the corpus callosum to the anterior commissure, and forming an anteroventral wall for the cavum septi pellucidi. Syn:: copula. lamina, spiral see lamina, osseous spiral.

lamina suprastriata layer III [Vogt] of the cerebral cortex. lamina tangentialis layer I [Vogt] of the cerebral cortex. lamina terminalis anterior wall of the third ventricle, the most rostral median part of the central nervous system, between the anterior commissure and the optic chiasm. Syn: velum terminale.

Lancisi, Giovanni Maria [1654‑1720] Italian physician and anatomist. He described the longitudinal striae overlying the corpus callosum in 1711.

Langley, John Newport [1853‑1925] English physiologist noted for his investigations of the autonomic nervous system. see ganglion, Langley's.

Lantermann, A. J. [19th century; fl. ~1875] anatomist at Strassburg. see incisure of Schmidt‑Lantermann; sometimes spelled as Lanterman.

law, Bell‑Magendie the ventral roots of spinal nerves are motor in function and the dorsal roots are sensory.

layer see also lamina; stratum. layer, anterior elastic see membrane, Bowman's.

layer, anterior limiting see membrane, Bowman's. layer, Bergmann astrocytes in the Purkinje layer of the cerebellum, which hypertrophy with degeneration of Purkinje cells.

layer[s] of the cerebellar cortex see cortex, cerebellar.

layer[s] of the cerebral cortex see cortex, cerebral.

layer, ependymal inner layer of the neural tube composed of germinal cells which undergo active mitosis.

layer, granular see cortex, cerebellar and cerebral

layer[s], infragranular layers V and VI of the cerebral cortex.

layer, mantle middle layer of the neural tube, composed of nuclei of developing nerve cells.

layer, marginal outer layer of the neural tube composed of the processes of the developing nerve cells.

layer, medullary any layer of white matter in the central nervous system, particularly the white matter deep to the cerebellar cortex

layer, molecular a superficial cortical layer, composed largely of nerve cell processes and relatively few cell bodies, a synaptic zone. Syn: plexiform layer. See also cortex. cerebellar and cerebral.

layer, plexiform see layer. molecular. see also retina.

layer, posterior elastic see membrane. Descemet's.

layer, posterior limiting see membrane, Descemet's.

layer[s] of the retina see retina.

layer, Sattler's vascular lamina of the choroid of the eye.

layer[s], supragranular layers I, II, and III of the cerebral cortex.

lemniscus [G. lemniskos—band or ribbon] one of the fiber bundles composed of secondary sensory fibers which arise in sensory nuclei and terminate in the thalamus.

lemniscus, lateral tract composed of fibers from the ventral and dorsal cochlear nuclei, and, with or without synapses in course, carrying auditory impulses to the medial geniculate nucleus and inferior colliculus.

lemniscus, medial tract composed mostly of fibers from nucleus gracilis and nucleus cuneatus carrying impulses for sense of position, vibratory sensibility and tactile discrimination to nucleus ventralis posterolateralis of the thalamus. Other fibers incorporated in this bundle are secondary gustatory fibers from nucleus solitarius [dorsal, visceral gray] and descending aberrant pyramidal fibers.

lemniscus, spinal lateral and ventral spinothalamic tracts.

lemniscus, trigeminal dorsal and ventral secondary ascending tracts of V.

lemnocyte neurolemma sheath cell.

lens transparent biconvex structure located immediately behind the pupil and adjacent to the posterior surface of the iris.

lenticular [L. lens—shaped] see fasciculus, lenticular; nucleus, lentiform.

leptomeninges pia mater and arachnoid, the thin membranous coverings of the brain and spinal cord. Syn: arachnopia; pia‑arachnoid

leptomeninx one layer of the leptomeninges.

ligament, coccygeal see filum terminale externum.

ligament, dentate ligament formed by the reflection of the pia‑arachnoid, attached medially along the spinal cord midway between the dorsal and ventral roots and laterally to the arachnoid and dura mater at the base of the skull and at intervals between the emerging spinal nerve roots at successive levels. Syn: denticulate ligament, ligamentum denticulaturn.

ligament, denticulate see ligament, dentate.

ligament, spiral thickened periosteurn of the outer bony wall of the cochlear canal, which provides the peripheral supporting wall of the cochlear duct and to which the basilar membrane is attached.

ligamentum denticulatum see ligament, dentate.

limb, anterior see capsule, internal, anterior limb.

limb, posterior see capsule, internal, posterior limb.

limbic [L. limbus—border] pertaining to certain gyri which surround the rostral portions of the brain stem and adjoining forebrain. see lobes of the cerebrum

limbic lobe system, limbic.

limbus the transition zone between the conjunctiva and sclera on the one hand and the cornea on the other.

limbus corticalis see cornu ammonis.

limbus laminae spiralis see limbus, spiral.

limbus, spiral thickening of the periosteum on the osseous spiral lamina in the cochlear duct. The tectorial membrane is attached along its upper margin. Syn: limbus laminae spiralis.

limbus spiralis see limbus, spiral.

limen insulae anterior aspect of the insula.

line see stripe.

linea splendens thickening of the pia mater along the midventral surface of the spinal cord. It encloses the anterior spinal artery.

lingula [L. little tongue] 1. most rostral subdivision of the cerebellar vermis, in the anterior medullary velum. 2. see gyrus, lingual.

lip, rhombic thickening at the junction of the alar and roof plates on each side of the rhombencephalon from which the flocculonodular lobe of the cerebellum develops.

lip, tympanic lower margin of the spiral limbus to which the basilar membrane of the cochlea is attached.

lip, vestibular upper margin of the spiral limbus to which the tectorial membrane is attached.

lipochrome see lipofuscin.

lipofuscin a yellowish pigment occurring as granules in the cytoplasm of some nerve cell bodies, particularly those of sensory and autonomic ganglia, and increasing in amount with age.

liquor cerebrospinalis see fluid, cerebrospinal.

liquor cotunnii see perilymph.

Lissauer, Heinrich [1861‑1891] German neurologist. see fasciculus, dorsolateral [Lissauer's tract].

lissencephalic having a smooth cerebrum without sulci and gyri.

lobe one of the major subdivisions of the cerebrum or cerebellum.

lobes of the cerebellum see cerebellum, lobes.

lobes of the cerebrum see cerebrum. lobes.

lobotomy operation in which the white matter of a cerebral lobe is incised.

lobules [lobulae] of the cerebellum see cerebellum, lobules [hemisphere, vermis].

lobule, inferior parietal subdivision of the parietal lobe, posterior to the postcentral sulcus, inferior to the intraparietal sulcus, and superior to the lateral fissure.

lobule, paracentral see gyrus, paracentral.

lobule, quadrate see precuneus. Subdivision of the parietal lobe, posterior to the postcentral sulcus and superior to the intraparietal sulcus.

locus ceruleus [N.A.] [caeruleus, coeruleus] area in the rostral and lateral part of the floor of the fourth ventricle, overlying the nucleus of locus ceruleus, the cells of which contain pigment [probably melanin] in their cytoplasm. This nucleus is said to be related to the control of general bodily vegetative functions and of REM [rapid eye movement; paradoxical] sleep.

loop, Archambault’s see loop, temporal, of the optic radiation.

loop, Cushing’s see loop, temporal, of the optic radiation.

loop, Flechsig’s see loop, temporal, of the optic radiation,

loop, gamma a series of neurologic connections whereby normal muscle tone is maintained. It is a three-neuron chain. The first neuron, the gamma motor neuron [a small ventral horn cell] is stimulated by descending spinal cord fibers and causes small intrafusal fibers of a muscle spindle to contract. The second, with stretch receptors in the spindle, is an afferent neuron which synapses directly on the third, an alpha motor neuron [large ventral horn cell] which, in turn causes the extrafusal muscle fibers to develop force and contract the muscle.

loop, Meyer’s see loop, temporal, of the optic radiation.

loop, temporal, of the optic radiation fibers of the optic radiation which arise from the lateral half of the lateral geniculate nucleus and course around the anterior end of the inferior horn of the lateral ventricle before turning back to enter the occipital lobe. Syn: Archambault’s loop; Cushing’s loop; Flechsig’s loop; Meyer’s loop.

Ludwig, K.F.W. [1816‑1895] German physiologist. Ludwig’s ganglion is a ganglion associated with the cardiac plexus.

Lugaro, intermediate cell[s] of see cell[s], intermediate, of Lugaro.

Luschka, Hubert von [1820‑1875]German anatomist who described the lateral apertures of the fourth ventricle [foramina of Luschka about 1863. see also nerve.

Luys, Jules Bernard [1828‑1898] French physician for whom the subthalamic nucleus was named [body of Luys],

lyra of David hippocampal commissure and adjacent portions of the fornix. Syn: psalterium.

m

macroneuron neuron with a large cell body and a long axon which synapses in some other region of the brain.

macula acustica oval thickened area in the utricle [macula utriculi and in the saccule [macula saccule which constitutes the sensory end organ in each of these vesicles.

macula lutea oval, yellowish area in the posterior part of the retina about 2.5 mm lateral to the optic papilla. It is devoid of all but capillary‑size blood vessels and contains the fovea centralis.

macula sacculi sensory end organ of the saccule. It is an oval, thickened area in the anteromedial part of the wall of the saccule, lying in a sagittal plane. From its surface cilia project laterally into an otolithic membrane.

macula utriculi sensory end organ of the utricle. It is an oval, thickened area in the anterolateral part of the wall of the utricle, lying roughly in the plane of the base of the skull. From its surface cilia project vertically upward into an otolithic membrane.

Magendie, Francçois [1783‑1855] French physiologist. He confirmed Bell's earlier findings that the ventral roots are motor and determined that the dorsal roots are sensory [about 1820]. see law, Bell‑Magendie. He also described the cerebrospinal fluid and a median aperture of the fourth ventricle [foramen of Magendiel] in 1825.

magnocellular composed of large cells; refers to specific layers of the lateral geniculate body.

Magnus, Rudolph [1873‑1927] German pharmacologist noted for his investigations of postural mechanisms, described in 1924.

malformation, Arnold‑Chiari see Arnold‑Chiari malformation.

mammillary body [L. mamilla—little breast] see body, mammillary.

Marchi, Vittorio [1851‑1908] Italian physician and anatomist who developed a technique for staining degenerating nerve fibers and so contributed to the establishment of the neuron theory. see method, Marchi.

massa intermedia [B.N.A.] midline nuclear mass interconnecting the two dorsal thalami across the third ventricle. Syn: adhesio interthalamica; interthalamic connexus; middle commissure; soft commissure.

mater, dura see dura mater.

mater, pia see pia mater.

matter, gray that subdivision of the tissue of the central nervous system, composed largely of neuropil and the cell bodies of neurons.

matter, white that subdivision of the tissue of the central nervous system, composed largely of myelinated nerve fibers.

Mauthner, L. [1840‑1894] Austrian ophthalmologist. Mauthner cells are giant cells in the medulla oblongata of fishes.

meatus, internal auditory [L. meatus‑channel] opening on the posteromedial surface of the petrous part of the temporal bone, through which the facial and acoustic nerves pass, accompanied by an internal auditory artery.

Meckel, Johann Friedrich [1714‑1774] German anatomist who described the pterygopalatine ganglion [Meckel's ganglion] in 1748. He also described the submandibular ganglion [Meckel's lesser ganglion] and the space in the dura mater for the semilunar ganglion, cavum trigeminale [Meckel's cavity].

median eminence see eminence, median.

medulla [ L.—marrow] see medulla oblongata.

medulla, cerebellar white matter of the cerebellum, between the cerebellar cortex and the deep cerebellar nuclei.

medulla, closed caudal portion of the medulla oblongata containing the rostral part of the central canal.

medulla oblongata [L. oblongus—oblong] caudal subdivision of the hindbrain interposed between the spinal cord and the pons. Syn: bulb; medulla; myelencephalon.

medulla, open rostral portion of the medulla oblongata serving as a floor for the caudal part of the fourth ventricle.

medulla spinalis see cord, spinal.

medullary pertaining to the medulla oblongata.

medullary 1. pertaining to the myelin sheath of nerve fibers. 2. medullar.

medullated see myelinated.

medullation see myelination.

meiosis see miosis.

Meissner, Georg [1829‑1905] German anatomist and physiologist. He described tactile corpuscles [Meissner’s corpuscles and the submucosal plexus [Meissner’s plexus] in 1853.

membrana limitans gliae membrane formed by the foot processes of astrocytes on capillaries of the central nervous system. see also glia limitans.

membrane, arachnoid see arachnoid.

membrane, basilar membrane composed of auditory strings, suspended between the osseous spiral lamina and the spiral ligament and on which the organ of Corti is located. Syn: membranous spiral lamina.

membrane, Bowman's anterior elastic lamina between the anterior epithelium and the substantia propria of the cornea. Syn: anterior elastic or limiting layer; lamina limitans anterior.

membrane, Bruch's see membrane, glassy.

membrane, Descemet's posterior elastic membrane between the substantia propria of the cornea and the endothelium on its posterior surface. Syn: lamina limitans posterior.

membrane, external limiting see membrane, superficial glial.

membrane, glassy refractile, hyaline layer in the eye between the choriocapillary layer of the choroid and the pigment epithelium of the retina for which it constitutes a basement membrane. Syn: Bruch's membrane.

membrane, internal limiting membrane underlying the ependyma of the ventricular spaces of the central nervous system. It consists of astrocytes and their processes intermingled with the processes of the ependymal cells.

membrane, otolithic thick, gelatinous layer overlying each macula acustica, into which cilia project from the macular surface and which also contains otoliths.

membrane, pupillary membrane which covers the pupil in the embryo. It is continuous with the substantia propria of the iris. Normally, in man, it disappears before birth.

membrane, Reissner’s see membrane, vestibular.

membrane, secondary tympanic membrane which closes the round window of the ear between the scala tympani and the tympanic cavity.

membrane, superficial glial membrane at the surface of the brain and spinal cord consisting of foot plates of astrocytes which are attached to the pia mater. Syn: external glia limitans; external limiting membrane.

membrane, tectorial flexible, gelatinous membrane attached along the vestibular lip of the limbus laminae spiralis and which overlies the rest of the organ of Corti throughout the length of the cochlear duct.

membrane, vestibular membrane separating the cochlear duct from the scala vestibuli in the cochlea. Syn: Reissner's membrane.

meninges [Gr. meninx, pl. meninges—membrane] membranous coverings of the brain and spinal cord.

meningocele saclike protrusion of skin and meninges through a vertebral or cranial defect.

meningoencephalocele abnormality in which both the brain and its meninges are herniated through a defect in the skull.

meningomyelocele saclike protrusion of skin, meninges, and spinal cord through a vertebral defect,

meninx [Gr. membrane] one of the membranous coverings of the brain and spinal cord.

Merkel, F. S. [1845‑1919] German anatomist. Merkel’s tactile discs are specialized intraepithelial nerve endings consisting of small, cuplike nerve fiber terminations and the modified epithelial cells on which they end.

mesencephalon [Gr. inesos—middle; enkephalos—brain] middle segment of the three‑vesicle embryonic brain and its adult derivative, Syn: midbrain.

mesocele lumen of the developing mesencephalon.

mesoglia see microglia.

metathalamus that division of the dorsal thalamus related to vision and hearing, comprising the lateral and medial geniculate bodies.

metencephalon most rostral subdivision of the hindbrain, comprising the pons and cerebellum.

method, Marchi a technique whereby degenerating myelin in nerve fibers separated from their cell bodies is selectively stained black by osmic acid but normal or completely degenerated myelin is left uncolored.

Meyer's loop see loop, temporal, of the optic radiation.

Meynert, Theodor Hermann [1833‑1892] Austrian psychiatrist and neurologist of Vienna who made many contributions to the study of the nervous system. He described the dorsal tegmental decussation in 1869 [Meynert's decussation]. He also described association fibers of the cerebrum, one of the supraoptic decussations [commissure of Meynert], fasciculus retroflexus [Meynert’s bundle or fasciculus], and substantia innominata [Meynert's basal nucleus or ganglion].

microglia neuroglial cells of mesodermal origin which, in the resting state, have small elongated, triangular, or kidney‑shaped nuclei and scanty cytop!asm but which enlarge and become phagocytic in many pathologic conditions. Syn: Hortega cell; mesoglia; rod cell.

microneuron neuron with a small cell body and a short axon which terminates in the same substructure of the brain.

midbrain see mesencephalon.

miosis [meiosis, myosis] /mi“-o'sis/ [Gr. meiosis—lessening] marked pupillary constriction.

mitochondria granular or filamentous organoids found in the cell bodies and processes of neurons and in other cells.

mitral cell see cell, mitral.

modality /mo-da“l'i“-te“/// form of sensation, such as touch, pain, vision, hearing.

modiolus /mo“d-di“o‑lus/ [L. hub of a wheel] bony core of the cochlea through which the cochlear nerve passes.

Monakow, Constantin von [1853‑1930] Russian neurologist in Zurich. For nucleus of Monakow, see nucleus, lateral cuneate; for tract of Monakow, see tract, rubrospinal.

monoplegia paralysis of one limb.

Monro, Alexander [1733‑1817] the second of three Scottish anatomists of the same name. He described the interventricular foramen [foramen of Monro] in 1797.

monticulus /mo“n-ti“k'u“-lus/ [L. small eminence] segment of the cerebellar vermis consisting of the culmen, clivus, and folium vermis.

mossy fibers see fiber[s], mossy.

motoneuron see neuron, motor.

motor unit a motor neuron and the muscle fibers which it supplies.

muscle, Bowman's radial fibers of the ciliary muscle.

muscle, Brücke’s see Brücke, E.W.R.

mydriasis /mi“d-ri’“'-a-sis/ dilatation of the pupil.

myelencephalon see medulla oblongata.

myelin [Gr. myelos—marrow] white, fatty substance which forms a sheath round the neuraxis of some central and peripheral nerve fibers.

myelinated having a myelin or medullary sheath. Syn: medullated.

myelination process whereby a nerve fiber acquires its myelin sheath. Syn: medullation.

myelitis, transverse transection of the spinal cord.

myeloarchitectonic pertaining to the myeloarchitecture [fiber and myelin structure] of the central nervous system.

myeloarchitectonics see myeloarchitecture.

myeloarchitecture architecture of the central nervous system according to the pattern of its myelinated nerve fibers. Syn: myeloarchitectonics.

myelogram roentgenogram of the spinal subarachnoid space following introduction of air or radioopaque oil.

myelomere [Gr. myelos —marrow; meros—part]

myelon see cord, spinal.

myeloschisis advanced and ultimately fatal form of spina bifida in which the spinal cord is represented by a wide‑open exuding shiny mass which has protruded entirely through the vertebral defect.

myenteric plexus see plexus, myenteric.

myoclonus, palatal rhythmic contractions of the palate after a lesion of the inferior olivary nucleus or the pontine portion of the central tegmental tract or sometimes the dentate nucleus. Syn: palatal nystagmus.

myosis see miosis.

n

narcolepsy disorder characterized by paroxysmal and recurrent diurnal attacks of irresistible sloop and drowsiness.

neocerebellum cerebellar hemispheres exclusive of the flocculi. Syn: pontocerebellum.

neoolive lateral portion of the inferior olivary nucleus.

neopallium cerebral cortex and its underlying white matter, exclusive of the pyriform area [paleopallium] and of the hippocampal formation [archipallium]. It develops primarily through the elaboration of nonolfactory functions and, in humans, forms the major portion of the pallium.

neostriatum caudate nucleus and putamen. see also striatum.

nerve bundle of peripheral nerve fibers bound together into one or more fascicles by connective tissue investments.

nerve, abducens [abducent] cranial nerve VI which arises mainly from cells in the abducens nucleus in the pons. Its fibers emerge from the ventral surface of the brain stem at the junction of the pons and medulla. After leaving the posterior fossa the nerve traverses the cavernous sinus and enters the orbit through the superior orbital fissure to supply the lateral rectus muscle of the eye.

nerve, accessory cranial nerve ]a, composed of a spinal portion which arises from the cervical spinal cord and a bulbar portion, from the closed medulla.

nerve, acoustic cranial nerve VIII, composed of a cochlear and a vestibular division from the internal car. It passes through the internal auditory meatus and joins the brain stem just lateral to the facial nerve at the cerebellopontine angle. Syn: auditory nerve; nervus acusticus; statoacoustic nerve; vestibulocochlear; auditory-vestibular; vestibuloacoustic nerve.

nerve, Arnold's auricular branch of the vagus nerve.

nerve, auditory see nerve, acoustic.

nerve, axillary branch of the posterior cord of the brachial plexus, supplying the deltoid muscle and overlying skin. Syn: circumflex nerve.

nerve, Bells long thoracic nerve

nerve, bulbar accessory part of the cranial nerve XI which arises from visceral motor nuclei in the closed medulla and which joins the vagus nerve and supplements its motor components.

nerve, carotid sinus branch of the glossopharyngeal nerve carrying afferent fibers from the carotid sinus and carotid body. Syn: Hering's nerve.

nerve cell 1. see neuron: 2. see body. cell.

nerve, cervical any of eight spinal nerves on each side of the spinal cord. They are formed by the fusion of dorsal and ventral roots and emerge from the spinal column between the skull and first cervical vertebra [nerve C₁, between cervical vertebrae [nerves C₂‑C₇], and between the seventh cervical and the first thoracic vertebra [nerve C₈].

nerve, cervical sympathetic that portion of the sympathetic trunk between the superior cervical ganglion above, and the middle and inferior cervical ganglia below.

nerve, circumflex see nerve, axillary.

nerve, cochlear cochlear division of the acoustic nerve, composed of fibers arising in the organ of Corti and ending in the cochlear nuclei of the brain stem.

nerve component see component, nerve.

nerve, cranial any nerve which arises from or joins the brain. see nerve, first cranial, etc.

nerve, Cruveilhier's see nerve, vertebral.

nerve, deep petrosal branch of the internal carotid plexus which joins the greater superficial petrosal nerve to form the nerve of the pterygoid canal. It consists of postganglionic sympathetic fibers from the superior cervical ganglion to the lacrimal and nasopalatine glands and their blood vessels.

nerve, dorsal any thoracic nerve.

nerve, eighth cranial see nerve, acoustic.

nerve, eleventh cranial see nerve, accessory.

nerve ending see ending, nerve.

nerve, facial cranial nerve VII, it arises from the ventrolateral surface of the pons at its junction with the medulla. It enters the petrous bone through the internal auditory meatus and passes through the facial canal, and most of its fibers leave the skull through the stylohyoid foramen. It is composed mostly of fibers which supply the muscles of facial expression, preganglionic autonomic fibers for certain glands of the head and taste fibers from the anterior two‑thirds of the tongue.

nerve fiber see fiber, nerve.

nerve, fifth cranial see nerve, trigeminal.

nerve, first cranial see nerve, olfactory.

nerve, fourth cranial see nerve, trochlear.

nerve, glossopalatine see nerve, intermediate.

nerve, glossopharyngeal cranial nerve IX which emerges from the ventrolateral surface of the medulla just caudal to the attachment of the facial nerve and which leaves the cranial cavity by way of the jugular foramen. It contains visceral afferent nerve fibers important in the regulation of blood pressure and of respiration and others associated with sensation from the palate and pharynx, and with taste from the back of the tongue. It also supplies preganglionic parasympathetic fibers for the parotid gland and motor fibers for the stylopharyngeus muscle.

nerve, greater petrosal branch of the facial nerve which leaves the facial nerve at the geniculate ganglion, runs along a groove on the temporal bone then joins the deep petrosal nerve to form the nerve of the pterygoid canal. It consists partly of sensory fibers from a small area of the palate and mainly of preganglionic parasympathetic fibers which terminate in the pterygopalatine ganglion for relay to the lacrimal and nasopalatine glands. Syn: greater superficial petrosal nerve.

nerve, greater splanchnic. nerve composed primarily of preganglionic sympathetic fibers, usually from the fifth through the ninth thoracic cord levels [T₅‑T₉]. They pass through the chain ganglia without synapse, then through the diaphragm, and end in the celiac ganglion.

nerve, greater superficial petrosal see nerve, greater petrosal.

nerve, Hering's see nerve, carotid sinus.

nerve, hypoglossal cranial nerve XII which arises from cells in the hypoglossal nucleus in the medulla. Its fibers emerge from the medulla between the pyramid and the inferior olive, collect into a nerve trunk which leaves the posterior fossa through the hypoglossal canal. to supply the muscles of the tongue

nerve, intermediate visceral subdivision of the facial nerve which leaves the brain between the motor root of VII and the acoustic nerve, and which is composed of visceral afferent fibers, including taste, and preganglionic parasympathetic fibers. Syn: glossopalatine nerve; nerve of Sapolini; nerve of Wrisberg‑, nervus intermedius; thirteenth cranial nerve.

nerve, intrathoracic, of Kuntz variable nerve strand between the first and second [occasionally second and third] thoracic nerves, close to the sympathetic trunk, and which may bring sympathetic fibers from T₂ [or T₃] to the stellate ganglion.

nerve, Jacobson's 1. tympanic branch of the glossopharyngeal nerve. 2. see nerve, vomeronasal.

nerve of Kuntz see nerve, intrathoracic, of Kuntz.

nerve, least splanchnic nerve composed primarily of preganglionic sympathetic fibers, usually from the twelfth thoracic cord segment [T₁₂]. They pass through the chain ganglia without synapse, then through the diaphragm, and end in the aorticorenal ganglion.

nerve, lesser petrosal branch arising from the tympanic plexus of the glossopharyngeal nerve. It consists of preganglionic parasympathetic fibers from the inferior salivatory nucleus which terminate in the otic ganglion for relay to the parotid gland. Syn: lesser superficial petrosal nerve.

nerve, lesser splanchnic nerve composed primarily of preganglionic sympathetic fibers, usually from the tenth and eleventh thoracic cord segments [T₁₀, T₁₁]. They pass through the chain ganglia without synapse, then through the diaphragm, and end in the celiac and superior mesenteric ganglia and the adrenal medulla.

nerve, lesser superficial petrosal see nerve, lesser petrosal.

nerve, long ciliary any of several branches of the nasociliary nerve within the orbit. They are composed mainly of sensory fibers from the eyeball, but also contain postganglionic sympathetic fibers.

nerve, lumbar any of five spinal nerves formed by the fusion of dorsal and ventral roots on each side of the spinal cord. Each nerve emerges from the spinal column through the intervertebral foramen below the corresponding lumbar vertebra.

nerve, lumbar splanchnic nerve composed primarily of preganglionic sympathetic fibers, usually from the first three lumbar cord segments [L₁-L₃]. They pass through the chain ganglia without synapse, and end in the inferior mesenteric ganglion.

nerve, Luschka’s 1. posterior ethmoidal nerve. 2. meningeal branch of each spinal nerve which supplies structures within the spinal canal. Syn: sinuvertebral nerve.

nerve, musculospiral radial nerve.

nerve, musician's u1nar nerve, because it supplies muscles responsible for finer movements of the fingers.

nerve, ninth cranial see nerve, glossopharyngeal.

nerve, oculomotor cranial nerve III, composed primarily of nerve fibers which arise from the oculomotor and the Edinger‑Westphal nuclei in the midbrain. It emerges from the interpenduncular fossa of the midbrain, passes between the posterior cerebral and superior cerebellar arteries, traverses the cavernous sinus, and enters the orbit through the superior orbital fissure to supply most of the extraocular muscles and the parasympathetic innervation for the ciliary muscle and the constrictor muscle of the iris.

nerve, olfactory cranial nerve I, composed of fine unmyelinated nerve fibers which arise from the olfactory mucosa, pass through the perforations in the cribriform plate, and terminate in the olfactory bulb.

nerve of Oort efferent fibers of the acoustic nerve which leave the brain stem with the vestibular nerve and join the cochlear nerve to end in the organ of Corti.

nerve, optic cranial nerve II, composed of nerve fibers which arise in the retina. It leaves the orbit through the optic foramen and reaches as far as the optic chiasm where some of its fibers cross the midline.

nerve, pelvic preganglionic autonomic fibers from sacral spinal cord segments 2, 3, and 4 for parasympathetic innervation of the descending and sigmoid colon, pelvic viscera, and genitalia, but excluding the gonads. Syn: nervus erigens; pelvic splanchnic nerve.

nerve, phrenic [Gr. phren—diaphragm] nerve arising primarily from cervical spinal cord segments 4, 5, and 6. Its fibers are part of the cervical plexus, and traverse the thorax to supply the diaphragm.

nerve, pneumogastric [Gr. pneumon—lung; gaster—stomach] see nerve, vagus.

nerve of the pterygoid canal the branches of the greater petrosal and the deep petrosal nerves as they pass through the pterygoid canal. Syn: Vidian nerve.

nerve root fascicle of nerve fibers of a cranial or spinal nerve, either within the brain or spinal cord or in the subarachnoid space.

nerve, sacral any of five spinal nerves formed by the fusion of dorsal and ventral roots on each side within the sacrum, where they divide into anterior and posterior primary rami, which emerge through the anterior and posterior sacral foramina respectively.

nerve of Sapolini see nerve, intermediate.

nerve, Scarpa's nasopalatine nerve.

nerve, second cranial see nerve, optic.

nerve, seventh cranial see nerve, facial.

nerve, short ciliary any of six to ten small nerves which run from the ciliary ganglion to the eyeball. They are composed predominantly of postganglionic parasympathetic, postganglionic sympathetic, and sensory fibers.

nerve, sinuvertebral see nerve, Luschka's, 2.

nerve, sixth cranial see nerve, abducens.

nerve, spinal nerve formed the intervertebral foramen by the fusion of the dorsal and ventral roots of each spinal cord segment and consisting of the fibers which innervate structures that develop at the same segmental level.

nerve, spinal accessory part of cranial nerve XI, which arises from cells in the accessory nucleus of the cervical spinal cord. The axons of these cells emerge from the lateral surface of the cord between the dorsal roots and dentate ligament, then collect into a fascicle which turns rostrally and passes through the foramen magnum to enter the cranial cavity. With the bulbar portion of the accessory nerve and the vagus nerve, the spinal accessory nerve leaves the cranial cavity through the jugular foramen. Its fibers supply the trapezius and sternocleidomastoid muscles. Its long course through the subarachnoid space makes it especially susceptible to any irritants in the cerebrospinal fluid. Syn: nerve of Willis.

nerve, [Gr. splanchna—viscera] any of the nerves composed primarily of preganglionic sympathetic fibers which arise in the spinal cord, pass through sympathetic chain ganglia without synapse, and terminate in relation to postganglionic neurons of the collateral ganglia. There are four splanchnic nerves: the greater, lesser, least, and lumbar splanchnic nerves. Sometimes the pelvic nerve, consisting of parasympathetic fibers from the sacral spinal cord, is called the pelvic splanchnic nerve.

nerve, stapedius branch of the facial nerve which supplies the stapedial muscle of the middle ear.

nerve, statoacoustic see nerve, acoustic.

nerve, tenth cranial see nerve, vagus.

nerve, third cranial see nerve, oculornotor.

nerve, thirteenth cranial see nerve, intermediate.

nerve, thoracic any of 12 spinal nerves formed by the fusion of dorsal and ventral roots from the thoracic spinal cord. Each nerve emerges from the spinal column through the intervertebral foramen below the corresponding thoracic vertebra.

nerve, trifacial see nerve, trigeminal.

nerve, trigeminal cranial nerve V, it leaves the lateral surface of the pons and just peripheral to its ganglion, it divides into three branches which leave the cranial cavity by different routes. It is composed primarily of motor fibers which arise in the motor nucleus of V in the pons and supply the muscles of mastication and of fibers for cutaneous sensibility from the face and oral cavity which end in sensory nuclei in the pons, medulla, and spinal cord. Syn: trifacial nerve.

nerve, trochlear cranial nerve IV, a slender nerve fascicle whose fibers arise primarily from cells in the trochlear nucleus of the midbrain. It crosses the midline through the anterior medullary velum at the junction of the pons and midbrain, courses around the midbrain, traverses the cavernous sinus, and enters the orbit through the superior orbital fissure to supply the superior oblique muscle. Syn: nervus patheticus.

nerve, twelfth cranial see nerve, hypoglossal.

nerve, tympanic . parasympathetic and visceral afferent nerve fibers which leave the glossopharyngeal nerve just outside the jugular foramen, pass upward into the middle car cavity, and join the tympanic plexus.

neurocele [neurocoele] cavity extending through the neural tube. Syn: neural canal

nerve, vagus [L. vagus—wandering] cranial nerve X, it arises by fascicles from the ventrolateral surface of the medulla and passes through the jugular foramen. Its branches supply the musculature of the palate, pharynx, and larynx. It also contains taste fibers from the epiglottis, preganglionic parasympathetic fibers, and visceral afferent fibers for thoracic and most abdominal viscera. Syn: nerve, pneumogastric. see also ganglia, jugular and nodose.

nerve, vertebral strands of fibers, mostly postganglionic sympathetic, that arise from cells in the vertebral and stellate ganglia. It is located dorsal to the vertebral artery. Syn: Cruveilhier's nerve.

nerve, vestibular vestibular division of the acoustic nerve, consisting of a superior branch composed of fibers from the cristae ampullares of the horizontal and superior semicircular ducts, the macula utriculi and a small part of the macula sacculi, and an inferior branch from the crista ampullaris of the posterior semicircular duct and the major portion of the macula sacculi. The fibers end in the vestibular nuclei of the brain stem and in the cerebellum.

nerve, vestibulocochlear see nerve. acoustic,

nerve, Vidian see nerve of the pterygoid canal.

nerve, vomeronasal nerve composed of unmyelinated fibers arising from specialized epithelium of the nasal septum [vomeronasal organ] and terminating in an accessory olfactory bulb. It is present in many adult mammals and some human embryos. but not in adult man. Syn: nerve of Jacobson.

nerve of Willis see nerve, spinal accessory.

nerve of Wrisberg 1. see nerve, intermediate. 2. medial cutaneous nerve of the arm.

nervus acusticus see nerve, acoustic.

nervus erigens see nerve, pelvic.

nervus intermedius see nerve, intermediate.

nervus patheticus see nerve, trochlear.

nervus terminalis small nerve, presumably containing autonomic and sensory fibers, which arises from nasal epithelium [but not from olfactory epithelium or the vorneronasal organ] and enters the brain through the lamina terminalis just below the anterior commissure. It is present in many vertebrate forms including man.

net, neurokeratin see neurokeratin.

neural pertaining to the nervous system or nervous tissue. For neural canal; cavity, crest, fold, groove: plate; tube, see the nouns.

neuraxis 1. long cytoplasmic extension of a nerve cell body. Syn: axis cylinder; neuraxon; neurite. 2. see system, central nervous.

neuraxon see neuraxis, 1.

neurilemma see neurolemma.

neurite see neuraxis, 1.

neurobiotaxis the tendency of nerve cells to migrate during their development toward the principal source of their stimuli [Ariëns Kappers, 1914].

neuroblast [Gr. neuron—nerve; blastos—germ] primitive cell which is the forerunner of a neuron.

neurofibril one of the slender filaments within the cell body of a neuron and extending into all its processes.

neurofilament one of the slender, threadlike structures, about 100 Å in diameter, which am constituent parts of the neurofibrils.

neuroglia /nu“-ro“g’li-a/ [Gr. neuron—nerve; glia—glue] connective tissue of the central nervous system, including astrocytes, oligodendroglia, and microglia. Syn: glia; neuroglial cells.

neurohypophysis the pars nervosa or main portion of the posterior [neural] lobe of the pituitary gland. Hormones produced by neurosecretory cells of the hypothalamus are transported along fibers of the hypothalamohypophysial tract to the neurohypophysis, where they are released.

neurokeratin network visible in the myelin sheath of peripheral nerve fibers under certain conditions after removal of the lipid content of the myelin, It is a fraction of brain proteins isolated by Ewald and Kühne in 1877 and traditionally considered to be associated with the protein network of the myelin sheath.

neurolemma [neurilemma] [Gr. neuron—nerve; lemma—husk] outer ectodermal sheath of a peripheral nerve fiber. Syn: primitive sheath; sheath of Schwann.

neuromere transverse groove on the floor of the fourth ventricle of the embryonic hindbrain.

neuron [neurone] [Gr. nerve] the complete nerve cell, including the cell body and all its processes; the structural unit of the nervous system.

neuron, afferent neuron that conducts impulses toward the central nervous system.

neuron, alpha motor large motor neuron whose axon terminates on large extrafusal muscle fibers.

neuron, bipolar neuron with two processes, one axon and one dendrite.

neuron chain see chain, neuron.

neuron, efferent neuron which conducts impulses away from the central nervous system.

neuron gamma, motor small motor neuron whose axon, a gamma efferent fiber, terminates on the small intrafusal fibers of a muscle spindle.

neuron, intercalated see neuron., internuncial.

neuron, internuncial central nervous system neuron having a small cell body and short axon which ads as a short connecting link in a neuron chain. Syn: intercalated or intercalary neuron; interneuron; Golgi type II cell.

neuron, lower motor see neuron, motor.

neuron, motor neuron whose cell body is located in a motor nucleus in the central nervous system and which conducts impulses to motor end‑plates in skeletal muscle. Syn: lower motor neuron; motoneuron.

neuron, multipolar neuron having more than two processes, including one axon and more than one dendrite.

neuron, postganglionic . neuron of the autonomic nervous system whose cell body is located in an autonomic ganglion and which terminates in smooth or cardiac muscle or in glandular tissue.

neuron, preganglionic neuron of the autonomic nervous system whose cell body is located in a general visceral motor nucleus within the central nervous system and which terminates in an autonomic ganglion.

neuron, primary sensory sensory neuron which usually has its cell body in a ganglion outside the central nervous system. Its axon ends, without crossing the midline, in a central nervous system nucleus at the level, above the level, or below the level at which the fiber enters the central nervous system.

neuron, pseudounipolar see neuron, unipolar.

neuron, secondary sensory neuron having its cell body in a central nervous system nucleus. Its axon usually crosses the midline and ends in the dorsal thalamus.

neuron, sensory see neuron, primary sensory.

neuron, tertiary sensory sensory neuron having its cell body in a nucleus in the dorsal thalamus. Its axon ends in the homolateral cerebral cortex.

neuron, unipolar neuron having a single process which shortly divides into axon and dendrite. Syn: pseudounipolar neuron.

neuron, upper motor neuron of the pyramidal tract.

neuropil [Gr. neuron; pilos—felt] feltwork of the terminal processes of axons and dendrites interspersed among the nerve cells in the gray matter of the central nervous system.

neuroplasm cytoplasm of a neuron.

neuropodium [-podia] [Gr. neuron; podion—small foot] small, synaptic, bulblike nerve ending, applied to the surface of the cell body and dendrites of many neurons. Syn:. bouton[s] terminal [‑aux] ‑, end foot; end bulb of Held.

neuropore [Gr. neuron; poros—passage] opening at either end of the embryonic neural tube.

neurosecretory cells see cells, neurosecretory.

neurosecretory hormones see hormones, neurosecretory.

Neurotransmitter chemical substance released at the axonal termination of a neuron, and which functions in the transmission of an impulse across a synapse or at an effector organ. Neurotransmitters include such substances as acetylcholine, norepinephrine, serotonin, dopamine, and gamma‑aminobutyric acid [GABA]. Syn: transmitter substance.

neurotubules extremely fine filamentous structures, apparently tubular in form, visible within the cytoplasm of neurons by electron microscopy.

Nissl, Franz [1860‑1919] German neuropathologist and psychiatrist who discovered the cytoplasmic bodies [Nissl granules] in nerve cell bodies in 1884.

node, Aschoff‑Tawara see node, atrioventricular.

node, atrioventricular structure composed of specialized cardiac muscle fibers, located in the interatrial septum beneath the endocardium of the right atrium just above the opening of the coronary sinus. It is supplied by parasympathetic fibers mainly from the left vagus nerve which slow the ventricles, and sympathetic fibers from the cervical and upper 4 or 5 thoracic chain ganglia, mainly on the left side, which increase the rate and force of the ventricles. Syn: Aschoff‑Tawara node.

node, Flack's see node, sinoatrial.

node of Ranvier point along a peripheral nerve fiber at which the myelin sheath is discontinuous and at which the neurolemma dips in to the neuraxis.

node, sinoatrial structure composed of specialized cardiac muscle fibers, located in the upper part of the sulcus terminalis of the heart just anterior to the opening of the superior vena cava. It is the pacemaker of the heart and is supplied by parasympathetic fibers mainly from the right vagus nerve which slow the heart, and sympathetic fibers from the cervical and upper 4 or 5 thoracic chain ganglia mainly of the right side which increase the rate and force of the heart. Syn: Flack's node; Koch's node.

node of Tawara see node, atrioventricular.

nodule most caudal segment of the cerebellar vermis.

noradrenaline see norepinephrine.

norepinephrine neurotransmitter released at the termination of most postganglionic sympathetic fibers [not including the terminations on sweat glands]. Syn: noradrenaline.

notch, anterior cerebellar shallow anterior curve of the cerebellum overlying the fourth ventricle and the dorsal and dorsolateral portions of the pons and upper medulla.

notch, occipital slight concavity on the inferior surface of the cerebrum, between the occipital and temporal lobes.

notch, preoccipital see notch, occipital.

notch, posterior cerebellar marked indentation on the posterior surface of the cerebellum between the two cerebellar hemispheres, overlying the clivus, folium vermis, and tuber of the vermis and containing the falx cerebelli.

notch, tentorial see incisure of the tentorium.

notochord cord of mesodermal‑cells derived from the head process of the primitive streak. It induces the formation of the neural plate. Later it is replaced by the vertebral column, but a remnant of it becomes the nucleus pulposus. Syn: chorda dorsalis.

noyau centré médian of Luys see nucleus centromedianus [dorsal thalamus].

nucleolus, satellite small mass located within the nucleus of cells in females, usually applied to the, nuclear membrane and thought to be one heteropyknotic X chromosome. It was first described in nerve cells. Syn: Barr body.

nucleus 1. vesicular organoid which contains the chromatin material and in neurons a prominent nucleolus. 2. group of nerve cell bodies within the central nervous system.

nucleus, abducens group of somatic motor cells located in the dorsomedial part of the pontine tegmentum. its fibers pass ventrally and caudally to emerge lateral to the pyramidal tract between the pons and medulla and continue as the major portion of the abducens nerve to supply the lateral rectus muscle of the eye. Syn: external oculomotor nucleus; motor nucleus of VI.

nucleus, accessory [cord] special visceral motor nucleus located in the dorsolateral and lateral portions of the ventral horn of the cervical spinal cord at levels C₅ or C₆. Its fibers cross the lateral funiculus to emerge midway between the dorsal and ventral roots. They collect into fascicles which combine to form the spinal accessory nerve, which supplies the sternocleidomastoid and trapezius muscles.

nucleus, accessory abducens see nucleus, accessory facial.

nucleus, accessory cuneate see nucleus, lateral cuneate.

nucleus, accessory facial small cluster of cells in the pontine tegmentum between the main facial‑nucleus and the abducens nucleus, thought to supply the posterior belly of the digastric muscle, Syn: accessory abducens nucleus; dorsal facial nucleus.

nucleus accumbens ventromedial extension of the head of the caudate nucleus the base of the septum.

nucleus of ala centralis see nucleus, dorsal efferent.

nucleus alaris see nucleus, dorsal efferent.

nucleus alba old term for the decussation of the superior cerebellar peduncle in the tegmentum of the midbrain.

nucleus ambiguus column of special visceral motor cells in the ventrolateral portion of the medulla. It supplies motor fibers by way of the glossopharyngeal, vagus, and bulbar accessory nerves to skeletal musculature derived from the third and fourth visceral arches, i.e., the musculature of the pharynx, larynx and upper esophagus. Syn: ventral motor nucleus; ventral nucleus of the vagal nerve.

nucleus of ansa lenticularis see nucleus, entopeduncular.

nucleus, anterior [dorsal thalamus] group of nuclei subdivided into anterodorsal, anteroventral, and anteromedial nuclei and located within the anterior tubercle of the dorsal thalamus. Its main connections are afferent fibers from the mammillary body [mammillothalamic tract] and efferent fibers to the cingulate gyrus through the anterior thalamic radiation.

nucleus, anterior ventral [dorsal thalamus] see nucleus ventralis anterior [dorsal thalamus].

nucleus, anterodorsal [dorsal thalamus] see nucleus anterodorsalis.

nucleus anterodorsalis [dorsal thalamus] small nucleus belonging to the anterior nuclear group of the dorsal thalamus. It consists of darkly stained, closely packed cells dorsal to the anteroventral nucleus of the dorsal thalamus. Syn: anterodorsal nucleus. see also nucleus, anterior [dorsal thalamus].

nucleus, anterolateral [cord] see nucleus, ventrolateral [cord].

nucleus, anteromedial [cord] see nucleus, ventromedial [cord].

nucleus, anteromedial [dorsal thalamus] see nucleus anteromedialis [dorsal thalamus].

nucleus anteromedialis [dorsal thalamus] small nucleus of the anterior nuclear group of the dorsal thalamus. It is located ventral and medial to but is not sharply separated from the anteroventral nucleus of the dorsal thalamus. Syn: anteromedial nucleus. see also nucleus. anterior [dorsal thalamus].

nucleus anteroprincipalis [dorsal thalamus] combined nucleus anteromedialis and anteroventralis.

nucleus, anteroventral [dorsal thalamus] see nucleus anteroventralis.

nucleus, anteroventralis [dorsal thalamus]see nucleus anterodorsalis [dorsal thalamus] nucleus, anteroventralis [dorsal thalamus] largest of the three anterior nuclei of the dorsal thalamus, it makes up the greatest part of the anterior tubercle of the thalamus. Syn: anteroventral nucleus, see also nucleus anterior [do al thalamus].

nucleus, arcuate [dorsal thalamus] see nucleus ventralis posteromedialis [dorsal thalamus].

nucleus, arcuate [hypothalamus] small subependymal nucleus in the tuberal region of the hypothalamus. Fibers from this nucleus can be traced into the median eminence, where they terminate near sinusoids of the hypophysial portal system. Syn: infundibular nucleus.

nucleus, arcuate [medulla] nucleus adjacent to the pyramid in the medulla which sends its fibers to the cerebellum via the ventral superficial arcuate fibers and the stria medullares of the fourth ventricle. Syn: ventral arcuate nucleus. The rostral, larger part of this nucleus which becomes continuous with the pontine gray is also designated as nucleus precursorius pontis or nucleus conterminalis [dorsal to the pyramid].

nucleus, basal see ganglia, basal.

nucleus of Bechterew see nucleus, superior vestibular.

nucleus, Burdach’s see nucleus cuneatus.

nucleus, caudal red part of the deep tegmental gray of the midbrain, located at the level of the inferior colliculus, and consisting of cells resembling those of the large‑celled part of the red nucleus. Syn: nucleus mesencephalicus profundus, pars lateralis caudalis.

nucleus, caudate one of the basal ganglia, made up of a head which forms the lateral wall of the anterior horn of the lateral ventricle, a body overlying the lateral part of the dorsal thalamus, and a tail located above the inferior horn of the lateral ventricle.

nucleus, central [cord] cell group in the ventral horn of the cervical spinal cord [phrenic nucleus] and lumbosacral spinal cord [lumbosacral nucleus].

nucleus, central [dorsal thalamus] see nucleus centromedianus [dorsal thalamus].

nucleus, central inferior tegmental see nucleus, inferior central tegmental.

nucleus, central, of the oculornotor nerve midline cell group of the oculornotor complex, thought to subserve convergence and perhaps including cells which supply the medial rectus muscles. Syn: nucleus impar; nucleus medianus anterior; nucleus of Perlia.

nucleus, central superior tegmental see nucleus, superior central tegmental.

nucleus centralis [dorsal thalamus] see nucleus centromedianus.

nucleus centralis centralis see nucleus centromedianus [dorsal thalamus].

nucleus, centromédian [dorsal thalamus]see nucleus centromedianus [dorsal thalamus].

nucleus centromedianus [dorsal thalamus] largest of the intralaminar nuclei of the dorsal thalamus, it is located in the internal medullary lamina in the posterior part of the thalamus. It is connected mainly with other nuclei of the dorsal thalamus and with parts of the basal ganglia. Syn: central nucleus; centromedian nucleus; nucleus centralis; nucleus centrum medianum.

nucleus centrum medianum [dorsal thalamus] see nucleus centromedianus. nucleus, chief sensory, of V nucleus located lateral to the motor nucleus of V at the level of the incoming fibers of the trigeminal nerve. It receives tactile fibers from the face, by way of the trigeminal nerve. Axons from cells in this nucleus ascend bilaterally in the dorsal secondary ascending tract of V and contralaterally in the ventral secondary ascending tract of V, to terminate in nucleus ventralis posteromedialis of the dorsal thalamus. Syn: pontine trigeminal nucleus; superior sensory nucleus.

nucleus of Clarke see nucleus, dorsal, of Clarke.

nucleus, common oculornotor see nucleus, oculornotor.

nucleus conterminalis inconstant group of nerve cells between the inferior olivary nucleus and the pyramid in the medulla, separated from but probably related to the arcuate nucleus.

nucleus of corpus restiforme see nucleus, lateral cuneate.

nucleus cuneatus [N.A.] nucleus composed of medium and small cells in the lateral portion of the posterior column in the closed medulla. It receives tactile and proprioceptive fibers from the upper half of the body by way of fasciculus cuneatus. Axons from most of the cells in this nucleus cross the midline in the sensory decussation, ascend in the medial lemniscus, and terminate in nucleus ventralis posterolateralis of the dorsal thalamus. Syn: Burdach's nucleus.

nucleus of Darkschewitsch small nucleus located in the ventrolateral portion of the periaqueductal gray in the rostral part of the midbrain. Its main afferent connections are the lenticular fasciculus, from the globus pallidus via connections in the nucleus of the field of Forel, and ascending fibers of the medial longitudinal fasciculus from the vestibular nuclei. Its efferent connections enter the medial longitudinal fasciculus for discharge to motor nuclei of the brain stem and spinal cord. Syn: ventral nucleus of the posterior commissure.

nucleus, Deiters' see nucleus, lateral vestibular.

nucleus, deep cerebellar one of the nuclear masses located within the cerebellum from which most of the efferent fibers of the cerebellum arise. They are: the fastigial, globose, emboliform, and dentate nuclei.

nucleus, dentate largest and most lateral of the deep cerebellar nuclei, located in the cerebellar white matter. Syn: nucleus dentatus; lateral cerebellar nucleus.

nucleus of the descending tract of V see nucleus of the spinal tract of V.

nucleus, descending vestibular see nucleus, inferior vestibular.

nucleus, diffuse thalamic see nucleus, nonspecific thalamic [dorsal thalamus].

nucleus, dorsal accessory olivary nucleus located dorsal to the most medial part of the rostral portion of the inferior olivary nucleus. Its fibers terminate mainly in the contralateral anterior lobe vermis. Syn: lateral accessory olivary nucleus.

nucleus, dorsal, of Clarke large‑celled nucleus in the dorsal horn of the spinal cord at levels about C₈‑L₃. It discharges through the dorsal spinocerebellar tract to the cerebellum. Syn: nucleus of Clarke; nucleus dorsalis; thoracic nucleus.

nucleus, dorsal cochlear special somatic sensory nucleus located dorsal or dorsolateral to the inferior cerebellar peduncle in the rostral part of the medulla. It is composed of small cells and receives cochlear nerve fibers. Its axons pass medially under the floor of the fourth ventricle, deep to the stria medullaris. Some cross the midline and pass ventrolaterally to join the lateral lemniscus; others probably enter the homolateral lateral lemniscus. These fibers, with and without synapses in course, end mainly in the inferior colliculus, partly in the medial geniculate nucleus.

nucleus, dorsal efferent parasympathetic nucleus of the medulla, lateral or dorsolateral to the hypoglossal nucleus, composed of small cells supplying preganglionic fibers by way of the vagus [and bulbar accessory] nerves to terminal ganglia for relay to viscera of the thorax and abdomen. Syn: dorsal motor nucleus; dorsal vagal nucleus; nucleus of ala centralis; nucleus alaris.

nucleus, dorsal facial see nucleus, accessory facial.

nucleus, dorsal, of fasciculus solitarius see gray, dorsal visceral.

nucleus, dorsal lateral [dorsal thalamus]

nucleus. dorsal motor see nucleus. dorsal efferent.

nucleus, dorsal paramedian nucleus of the parahypoglossal gray composed of closely packed, small to medium‑sized cells in the medulla and caudal pons in a position medial or dorsomedial to the hypoglossal, prepositus. and caudal portion of the abducens nuclei. It is said to show retrograde degeneration with lesions of the cerebellum. Syn: nucleus paramedianus dorsalis.

nucleus, dorsal premammillary more or less discrete cell group rostral to the mammillary nuclei in many mammals but reduced to scattered cells in man.

nucleus, dorsal, of the raphe &A'W nucleus composed of closely packed, deeply staining cells in the ventral part of the periaqueductal gray throughout the level of the inferior colliculus and extending into the isthmus of the pons. It consists of lateral portions which fuse in the midline, giving the nucleus a butterfly shape in cross section. It is thought to receive some fibers from the cerebellum and others from the dorsal longitudinal fasciculus. Syn: supratrochlear nucleus.

nucleus, dorsal sensory see dorsal visceral gray.

nucleus, dorsal tegmental [of Marburg] nucleus located dorsal to the medial longitudinal fasciculus on the floor of the fourth ventricle in the isthmus and in the periaqueductal gray of the midbrain. It contributes fibers to the dorsal longitudinal fasciculus. Syn: nucleus of Gudden.

nucleus, dorsal, of the trapezoid body see nucleus, superior olivary.

nucleus, dorsal vagal see nucleus, dorsal efferent.

nucleus dorsalis [cord] see nucleus, dorsal, of Clarke.

nucleus dorsalis superficialis see nucleus lateralis dorsalis [dorsal thalamus]

nucleus dorsocaudalis [dorsal thalamus] see nucleus lateralis posterior.

nucleus dorsointermedius externus see nucleus lateralis posterior [dorsal thalamus].

nucleus, dorsolateral [cord] column of nerve cells in the lateral division of the ventral horn in a position indicated by its name, in the cervical and lumbosacral enlargements. Its fibers are thought to supply the muscles of the forearm and leg. Syn: posterolateral nucleus.

nucleus, dorsolateral tegmental see nucleus, laterodorsal tegmental.

nucleus dorsolateralis tegmenti see nucleus of locus ceruleus.

nucleus, dorsomedial [cord] column of nerve cells in the medial division of the ventral horn in a position indicated by its name, mostly at thoracic and upper lumbar spinal cord levels. Fibers from these cells are thought to supplement those from the ventromedial nucleus in the innervation of trunk musculature Syn: posteromedial nucleus.

nucleus, dorsomedial [dorsal thalamus] see nucleus dorsomedialis.

nucleus, dorsomedial [hypothalamus] nucleus located dorsal and somewhat rostral to the ventromedial hypothalamic nucleus, with which it functions in relation to emotional expression and food intake. It receives orbitohypothalamic and fimbria‑fornix fibers from the cerebral cortex and sends fibers to the cranial parasympathetic nuclei via the dorsal longitudinal fasciculus, nucleus dorsomedialis [dorsal thalamus] large nucleus located medial to the internal medullary lamina in the midregion of the dorsal thalamus. Its main afferent connections are from other diencephalic nuclei, probably for the integration [somatic and visceral impulses which it relays mainly to the prefrontal cortex by way of the anterior thalamic radiation. Syn: dorsomedial nucleus; nucleus dorsalis medialis; medial nucleus; nucleus medialis. see: nucleus lateralis dorsalis [dorsal

nucleus dorsooralis [dorsal thalamus] dorsal part of nucleus ventralis lateralis.

nucleus, Edinger‑Westphal parasympathetic nucleus of the oculomotor nerve, controls pupillary constriction and accommodation of the lens for near vision.

nucleus, emboliform cerebellar nucleus located close to the hilus of the dentate nucleus. Syn: nucleus emboliformis.

nucleus eminentiae teretis one of the parahypoglossal nuclei, located dorsomedial to the hypoglossal nucleus. Syn: nucleus funiculi teretis.

nucleus, entopeduncular strands of nerve cells within or adjoining the ansa lenticularis and which serve as a way station for fibers of that tract. Syn: nucleus of the ansa lenticularis.

nucleus, external cuneate see nucleus, lateral cuneate.

nucleus, external oculomotor see nucleus, abducens.

nucleus, facial group of specia.1 visceral motor cells in the caudal, ventrolateral part of the pontine tegmentum. Its fibers pass dorsomedially, then rostrally to hook over the abducens nucleus, then pass in a caudal, ventrolateral direction to leave the brain stem at the cerebellopontine angle, and continue as part of the facial nerve to supply the muscles of facial expression, derived from the second visceral arch. Syn: motor nucleus of VII.

nucleus fasciculosus [dorsal thalamus]medial part of nucleus ventralis anterior.

nucleus of fasciculus solitarius see nucleus solitarius.

nucleus, fastigial cerebellar nucleus underlying the vermis and located on either side of the fastigium of the fourth ventricle. Syn: nucleus fastigii; nucleus tecti; roof nucleus.

nucleus, filiform see nucleus, paraventricular [hypothalamus].

nucleus funiculi teretis see nucleus eminentiae teretis.

nucleus geniculatus lateralis see nucleus, lateral geniculate.

nucleus geniculatus medialis see nucleus, medial geniculate; the most beautiful nucleus in the brain.

nucleus, globose nucleus composed of several small groups of cells in the cerebellum, overlying the fourth ventricle and just lateral to the fastigial nucleus. Syn nucleus globosus.

nucleus of Goll see nucleus gracilis.

nucleus gracilis [N.A.] nucleus composed of medium and small cells in the medial portion of the posterior column in the closed medulla. It receives tactile and proprioceptive fibers from the lower half of the body by way of fasciculus gracilis. Axons from most of the cells in this nucleus cross the midline in the sensory decussation, ascend in the medial lemniscus, and terminate in the nucleus ventralis posterolateralis of the dorsal thalamus. Syn: nucleus of Gon.

nucleus of Gudden see nucleus, dorsal tegmental.

nucleus, gustatory see gray, dorsal visceral.

nucleus, hypoglossal cells of origin for motor fibers of the hypoglossal nerve supplying tongue muscle. It is located on either side of the midline in the medulla, on the floor of the fourth ventricle and ventrolateral to the central canal

nucleus impar see nucleus, central, of the oculomotor nerve.

nucleus, inferior central tegmental nucleus located on either side of the midline in the caudal portion of the pontine tegmentum. It may be a part of the respiratory area but its connections are unknown. nucleus, Inferior olivary nucleus in the ventrolateral portion of the medulla. It is shaped like a crumpled bag with its hilus directed medially or dorsomedially. Its fibers terminate mainly in the contralateral cerebellar hemisphere. Syn: principal olive; principal olivary nucleus. nucleus, Inferior salivatory parasympathetic nucleus of the medulla, rostral to the dorsal motor nucleus. It is composed of small cells supplying preganglionic fibers by way of the glossopharyngeal nerve to the otic ganglion for relay to the parotid

nucleus, inferior vestibular special somatic afferent [proprioceptive] nucleus located in the dorsolateral portion of the medulla, just medial to the inferior cerebellar peduncle. It receives mainly vestibular nerve fibers and fibers of' the spinovestibular tract. Axons from most of its cells enter the medial vestibulospinal tract bilaterally and terminate on cells of the accessory nucleus and to some extent other ventral horn cells in the cervical spinal cord. Syn: descending vestibular nucleus; spinal vestibular nucleus.

nucleus intercalatus [hypothalamus] dorsal division [Ingram] or ventral division [Le Gros Clark] of the lateral mammillary nucleus of Rose.

nucleus intercalatus [medulla] one of the parahypoglossal nuclei, it is composed mostly of small cells, interposed between the hypoglossal and dorsal efferent nuclei. Syn: nucleus of Staderini.

nucleus, latermediolateral column of small nerve cells which make up the lateral horn in the thoracic and upper three lumbar segments of the spinal cord. It consists of the cell bodies of preganglionic sympathetic nerve fibers.

nucleus, intermediomedial column of small nerve cells between the central canal and the lateral horn in the thoracic and upper three lumbar segments of the spinal cord. It consists of the cell bodies of preganglionic sympathetic nerve fibers.

nucleus intermedius see nucleus interpositus.

nucleus, internal medial mammillary nucleus. See nucleus, mammillary.

nucleus, interpeduncular midline nucleus in the ventral and caudal midbrain between the bases of the two cerebral peduncles. It receives fibers from the habenula and hypothalamus and sends fibers to the dorsal tegmental nucleus.

nucleus, interposed see nucleus interpositus.

nucleus interpositus nucleus located between the dentate and fastigial nuclei of the cerebellum in forms below primates and corresponding to the combined emboliform and globose nuclei of primates, including man. Syn: interposed nucleus, nucleus intermedius.

nucleus, interstitial, of Cajal see nucleus, interstitial, of the medial longitudinal fasciculus.

nucleus, interstitial, of the medial longitudinal fasciculus nucleus composed of fairly large cells interspersed among the fibers of the medial longitudinal fasciculus. Its main afferent connections are the lenticular fasciculus from the globus pallidus and ascending fibers of the medial longitudinal fasciculus from the vestibular nuclei. Its efferent fibers enter the medial longitudinal fasciculus for descending input to motor nuclei of the brain stem and spinal cord. Syn: interstitial nucleus, intralaminar [dorsal thalamus] any one of' the nuclei located along or within the internal medullary laminae of the dorsal thalamus, including nucleus centromedianus [the largest of the group], nucleus limitans, nucleus paracentralis, and nucleus centralis lateralis. Syn: nucleus intralamellaris.

nucleus intralamellaris [dorsal thalamus] see nucleus, intralaminar.

nucleus juxtasolitarius see nucleus parasolitarius.

nucleus, lacrimal scattered cells along the descending limb of the genu of the facial nerve in the caudal and lateral pontine tegmentum. It is a subdivision of the superior salivatory nucleus and supplies preganglionic parasympathetic fibers by way of the intermediate division of the facial nerve to the pterygopalatine ganglion, for relay to the lacrimal gland.

nucleus, lateral [dorsal thalamus] 1. group of nuclei whose main subdivisions are nucleus lateralis posterior, lateralis dorsalis, suprageniculatus, and the pulvinar. This group is present in all but the most anterior part of the dorsal thalamus. It is primarily interconnected with cortex of the parietal lobe. 2. see nucleus lateralis posterior [dorsal thalamus].

nucleus, lateral accessory olivary see nucleus, dorsal accessory olivary.

nucleus, lateral cerebellar see nucleus, dentate.

nucleus, lateral cervical [cord] nucleus present in cat but absent in man. It is located in the lateral funiculus of the spinal cord, lateral or ventrolateral to the dorsal horn, and may be a relay station to the cerebellum or to the thalamus.

nucleus, lateral cuneate large‑celled nucleus located dorsolateral and rostral to the cuneate nucleus. It receives fibers from fasciculus cuneatus. Dorsal superficial arcuate fibers arising from this nucleus enter the inferior cerebellar peduncle and terminate in the cerebellar vermis. Syn: accessory cuneate nucleus; external cuneate nucleus; nucleus of corpus restiforme; nucleus of Monakow.

nucleus, lateral geniculate [metathalamus] nucleus composed of alternating layers of cells and fibers and constituting a thalamic center for the visual system. Syn: nucleus geniculatus lateralis.

nucleus [ei] of the lateral lemniscus small groups of nerve cells adjacent to the lateral lemniscus and which receive fibers from and contribute fibers to it; contains three nuclei, specialized for monaural and binaural processing.

nucleus, lateral mammillary, of Le Gros Clark see nucleus lateralis of Le Gros Clark.

nucleus, lateral mammillary, of Rose small cell group located lateral to the medial mammillary nucleus and consisting of a ventral portion [nucleus lateralis of Ingram, nucleus intercalatus of Le Gros Clark] and a dorsal portion [nucleus intercalatus of Ingram, nucleus lateralis of Le Gros Clark]. see also nucleus, mammillary.

nucleus, lateral ventral [dorsal thalamus see nucleus, ventral lateral nucleus, lateral vestibular nucleus located in the dorsal part of the tegmentum lateral to the medial vestibular nucleus in the region of the pontomedullary junction. Its main afferent connections include vestibular nerve fibers from the horizontal semicircular duct and fibers from the fastigial nuclei of the cerebellum. Its main efferent connections consist of fibers of the ventrolateral vestibulospinal tract which arise from the large cells of this nucleus. Other efferent fibers enter the medial longitudinal fasciculus and supplement those from the medial vestibular nucleus. Syn: Deiter’s nucleus.

nucleus lateral posterior [dorsal thalamus] see nucleus lateralis posterior [dorsal thalamus] and nucleus, lateral [dorsal thalamus]

nucleus lateralis dorsalis [dorsal thalamus] most anterior of the lateral group, it is a small nucleus located on the superior surface of the dorsal thalamus dorsomedial to nucleus lateralis posterior and rostral to it. It appears to be related to the cortex in the inferior parietal area adjacent to the lateral fissure. Syn: dorsal lateral nucleus; nucleus dorsalis superficialis.

nucleus ventralis of Ingram [hypothalamus] ventral portion of the lateral mammillary nucleus of Rose. Syn: nucleus intercalatus of Le Gros Clark.

nucleus lateralis of Le Gros Clark [hypothalamus] dorsal portion of the lateral mammillary nucleus of Rose. Syn: nucleus intercalatus of Ingram.

nucleus lateralis posterior [dorsal thalamus] large nucleus of the lateral group, it is located lateral to the internal medullary lamina and extends from about the middle of the dorsal thalamus back to the pulvinar. It is interconnected mainly with the parietal lobe cortex behind the postcentral gyrus. Syn: lateral nucleus; nucleus dorsocaudalis; nucleus dorsointermedius externus; nucleus lateralis; posterior lateral nucleus.

nucleus, laterodorsal tegmental nucleus composed of nonpigmented cells in the laterodorsal tegmentum of the isthmus and caudal midbrain and in the adjoining midbrain periaqueductal gray. It sometimes is considered a part of the nucleus of the locus ceruleus with which its cells are intermingled. Syn: dorsolateral tegmental nucleus.

nucleus lateropolaris [dorsal thalamus] anterior.

nucleus, lateroventral tegmental cells located along the dorsal margin of the medial lemniscus in the pontine tegmentum, which are thought to send crossed and uncrossed fibers into the ventral reticulospinal tracts.

nucleus, lenticular see nucleus, lentiform.

nucleus, lentiform putamen and globus pallidus of the basal ganglia. Syn: lenticular nucleus.

nucleus of locus ceruleus [caeruleus] nucleus located beneath the floor of the fourth ventricle in the dorsolateral part of the tegmentum of the pontine isthmus. It is composed of medium‑sized cells with pigment granules [probably melanin] in their cytoplasm. See locus ceruleus. Syn: nucleus dorsolateralis tegmenti; nucleus pigmentosus.

nucleus, lumbosacral [cord] subdivision of the central nucleus in the lumbosacral enlargement [S₂], between the medial and lateral cell groups of the ventral horn. The peripheral distribution of its fibers is not known.

nucleus of Luys see nucleus, subthalamic.

nucleus magnocellularis basalis see nucleus, dorsal, of Clarke.

nucleus, mammillary nucleus consisting of two pans, a large medial mammillary nucleus and a small lateral mammillary nucleus, which together make up most of the mammillary body. Its main afferent connections include fibers of the fimbria fornix system and the mammillary peduncle [including the secondary ascending gustatory tract.]. Its main efferent connections include the mammillothalamic tract to the anterior nuclei of the dorsal thalamus, the mammillotegmental tract to the dorsal tegmental nucleus, and the mammillopeduncular tract to the interpeduncular nucleus, and lateral two‑thirds of nucleus ventralis

nucleus, medial [dorsal thalamus] 1. group of nuclei subdivided into the dorsomedial [or medial] nucleus, the nuclei of the habenulointerpeduncular tract, and the parafascicular nucleus. 2. see nucleus dorsomedialis [dorsal thalamus].

nucleus, medial accessory olivary nucleus located caudal and medial to the inferior olivary nucleus. Its fibers terminate mainly in the contralateral flocculus, vermis, and fastigial nucleus of the cerebellum. Syn: ventral accessory olivary nucleus.

nucleus, medial geniculate [metathalamus] nucleus located ventrolateral and rostral to the superior colliculus of the midbrain and constituting a thalamic center for the auditory system. The most beautiful nucleus in the brain. Syn:: nucleus geniculatus medialis.

nucleus, medial vestibular largest of the vestibular nuclei, located in the dorsal portion of the tegmentum in the area of the pontomedullary junction. Its main connections include vestibular nerve fibers from the horizontal semicircular duct, efferent fibers to the contralateral abducens and parabducens nuclei through the contralateral medial longitudinal fasciculus, vestibulocerebellar fibers to the flocculonodular lobe and the fastigial nuclei, and descending fibers by way of both medial longitudinal fasciculi to ventral horn cells in the cervical spinal cord. Syn: nucleus of Schwalbe; principal or triangular vestibular nucleus.

nucleus medialis [dorsal thalamus]see nucleus dorsomedialis [dorsal thalamus].

nucleus medialis dorsalis [dorsal thalamus] see nucleus dorsomedialis [dorsal thalamus].

nucleus medianus anterior see nucleus, central, of the oculornotor nerve.

nucleus, mesencephalic, of V large unipolar cells located mostly lateral to the periaqueductal gray of the midbrain, and ventrolateral to the fourth ventricle in the pons at trigeminal and isthmus levels. Peripheral processes [dendrites] from these cells carry proprioceptive impulses mostly from the muscles of mastication by way of the trigeminal nerve, but also from the extraocular muscles by way of the oculomotor and trochlear and perhaps the abducens nerves. Axons of these neurons terminate mainly in the motor nuclei of the corresponding nerves.

nucleus mesencephalicus profundus scattered cells and clusters of cells in the midbrain tegmentum, subdivided into parts according to their positions in relation to the red nucleus. Syn: deep tegmental gray.

nucleus, midline [dorsal thalamus] poorly differentiated [in man] group of nuclei that lie close to the third ventricle or which may fuse across the midline as a massa intermedia. It may be a link in an inhibitory path between cerebral cortex and lower centers.

nucleus minimus subdivision of the small‑celled portion of the red nucleus consisting of extremely small cells along the fiber bundles in the red nucleus. Their significance is unknown.

nucleus of Monakow see nucleus, lateral cuneate.

nucleus, motor, of III see nucleus, oculomotor.

nucleus, motor, of IV see nucleus, trochlear.

nucleus, motor, of V special visceral motor nucleus in the dorsolateral part of the pontine tegmentum. Its fibers pass ventrolaterally to emerge at a midpontine level and mark the lateral boundary of the pons. These fibers supply the muscles of mastication derived from the first visceral arch.

nucleus, motor, of VI see nucleus, abducens.

nucleus, motor, of VII see nucleus, facial.

nucleus, nonspecific thalamic [dorsal thalamus] usually any one of three groups of nuclei including the intralaminar, midline, and reticular nuclei. They are sometimes also called the unspecific, reticular, diffuse or recruiting nuclei of the dorsal thalamus.

nucleus, oculomotor somatic motor nucleus in the midbrain whose fibers enter the oculornotor nerve to supply the levator palpebrae muscle and all the extraocular eye muscles except the superior oblique and lateral rectus muscles. Syn: motor nucleus of III.

nucleus, olivary see nucleus, inferior olivary; dorsal accessory olivary; and medial accessory olivary.

nucleus papilliformis rostral continuation of the inferior central tegmental nucleus located next to the midline in the caudal pontine tegmentum. Its connections and function are unknown.

nucleus, parabducens small cells next to or intermingled with the cells of the abducens nucleus and concerned with horizontal conjugate eye movements. Its fibers enter the medial longitudinal fasciculus, probably of the opposite side, to end in the oculomotor nucleus for relay to the medial rectus muscle.

nucleus, parabigeminal nucleus superficial to the lateral lemniscus at the level of the inferior colliculus. Axons of some of its cells presumably terminate in the lateral nuclei of the pons.

nucleus, parahypoglossal any one of a group of nuclei which form a ring of cells around the hypoglossal nucleus, consisting primarily of the nucleus of Roller, the dorsal paramedian nucleus, nucleus eminentiae teretis, nucleus intercalatus, and nucleus prepositus. Syn: parahypoglossal gray; perihypoglossal gray or nucleus.

nucleus, paramedianus dorsalis see nucleus, dorsal paramedian.

nucleus paramedianus oralis subdivision of the dorsal paramedian nucleus in the rostral portion of the medulla where the nucleus is particularly well developed.

nucleus parasolitarius subdivision of nucleus solitarius located just ventral and lateral to fasciculus solitarius in the medulla. It is a receptive area for general visceral afferent fibers from fasciculus solitarius. Syn: nucleus juxtasolitarius; parasolitary gray; ventral nucleus of fasciculus solitarius; ventral sensory nucleus.

nucleus, paraventricular [hypothalamus] elongated column of large, deeply staining cells located close to the third ventricle in the region between the optic chiasm ventrally and the hypothalamic sulcus dorsally. It is the probable source of oxytocin which is carried to the neurohypophysis along the hypothalamohypophysial tract. Syn: filiform nucleus.

nucleus, per1hypoglossal see nucleus, parahypoglossal.

nucleus of Perlia see nucleus, central, of the oculomotor nerve.

nucleus, phrenic cervical portion of the central nucleus of the spinal cord. Its cells, centrally placed in the ventral horn mainly in segments C₄‑C₆, send fibers into the phrenic nerve to supply the diaphragm.

nucleus pigmentosus see nucleus of locus ceruleus.

nucleus, pontine trigeminal see nucleus, chief sensory, of V.

nucleus, posterior [hypothalamus] area in the posterior part of the hypothalamus between the mammillary body ventrally and the hypothalamic sulcus dorsally. Its afferent connections are, at least in part, from the posterior orbital and premotor cortices. Its main functions appear to be autonomic regulation [parasympathetic, through the dorsal longitudinal fasciculus; sympathetic, through nucleus, reticular [dorsal thalamus] [hypothalamotegmental and tegmentospinal paths] and regulation of body temperature against cold [through hypothalamotegmental connections].

nucleus of the posterior commissure cells located adjacent to the posterior commissure. It is sometimes subdivided into a dorsal portion or nucleus on either side of the midline at the dorsal edge of the periventricular gray, an interstitial nucleus intermingled with the fibers of the commissure and a ventral nucleus, the nucleus of Darkschewitsch.

nucleus, posterior lateral [dorsal thalamus] see nucleus lateralis posterior [dorsal thalamus].

nucleus, posterior marginal thin layer of large cells arranged tangentially on the apical surface of the dorsal horn of the spinal cord.

nucleus, posterior ventral [dorsal thalamus] see nucleus ventralis posterior [dorsal thalamus].

nucleus, posterolateral [cord] see nucleus, dorsolateral [cord].

nucleus, posterolateral ventral [dorsal thalamus] see nucleus ventralis posterolateralis [dorsal thalamus].

nucleus posterolateralis ventralis [dorsal thalamus] see nucleus ventralis posterolateralis [dorsal thalamus].

nucleus, posteromedial [cord] see nucleus, dorsomedial [cord].

nucleus, posteromedial ventral [dorsal thalamus] see nucleus ventralis posteromedialis [dorsal thalamus].

nucleus, posteromedialis ventralis [dorsal thalamus] see nucleus ventralis posteromedialis [dorsal thalamus].

nucleus, postposterolateral [cord] see nucleus, retrodorsolateral [cord].

nucleus praepositus see nucleus prepositus.

nucleus precursorius pontis [rostral], enlarged portion of the arcuate nucleus of the medulla.

nucleus, pregeniculate small, crescent‑shaped cell group dorsal to, and overlying the anterior portion of the lateral geniculate nucleus.

nucleus prepositus [praepositus] one of the parahypoglossal nuclei located on the floor of the fourth ventricle in the lateral part of the medial eminence between the hypoglossal nucleus caudally and the abducens nucleus rostrally.

nucleus, principal olivary see nucleus, inferior olivary.

nucleus, principal vestibular see nucleus, medial vestibular.

nucleus proprius see gray, dorsal funicular.

nucleus, recruiting see nucleus, nonspecific thalamic, stimulation of which engages large areas of the cerebral cortex.

nucleus, red large nucleus in the rostral portion of the midbrain tegmentum and caudal part of the diencephalon. It receives fibers mainly from the cerebellum and from the cerebral cortex, globus pallidus, and ventral thalamus, and superior colliculus. Its caudal, large‑celled portion discharges caudally into the brain stem and cervical spinal cord. Its rostral, small‑celled portion discharges rostrally to the thalamus, mainly to nucleus ventralis lateralis. Syn: nucleus ruber.

nucleus, reticular [dorsal thalamus] 1. narrow layer of cells between the external medullary lamina of the thalamus and the internal capsule. Its cells resemble those of adjoining thalamic nuclei and ventrally it is continuous with the zona incerta. Functionally it is related to other thalamic nuclei, particularly the intralaminar group. It has been considered a way station between the multisynaptic ascending reticular system and the diffuse thalamocortical projection system, but more recently this role has been questioned. 2. The nonspecific nuclei, including mainly the reticular nucleus [see def. 1], and the intralaminar and midline nuclei.

nucleus retroambigualis group of nerve cells intermediate in position between the accessory nucleus of the spinal cord and nucleus ambiguus of the medulla, sometimes considered the caudal end of nucleus ambiguus.

nucleus, retrodorsolateral [cord] cell group in the lateral division of the ventral horn, dorsal or dorsolateral to the dorsolateral nucleus in the cervical and lumbosacral enlargements. Its fibers supply intrinsic muscles of the hand and foot. Syn: postposterolateral nucleus.

nucleus, retrofacial cluster of nerve cells interposed between nucleus ambiguus caudally and the facial nucleus rostrally.

nucleus of Roller large cells located ventral to the hypoglossal nucleus. It is one of the parahypoglossal nuclei. Syn: sublingual nucleus.

nucleus, roof see nucleus, fastigial.

nucleus ruber see nucleus, red.

nucleus of Schwalbe see nucleus, medial vestibular.

nucleus, semilunar see nucleus ventralis posteromedialis [dorsal thalamus].

nucleus solitarius gray matter associated with fasciculus solitarius. It is subdivided into dorsal visceral gray and nucleus parasolitarius. Syn: nucleus of fasciculus solitarius.

nucleus, spinal, of V see nucleus of the spinal tract of V.

nucleus, spinal accessory see nucleus, accessory [cord].

nucleus, spinal reticular cells interspersed among the fibers along the lateral margin of the dorsal horn in the cervical spinal cord.

nucleus of the spinal tract of V nucleus of the dorsolateral part of the medulla and caudal portion of the pons. It is continuous rostrally with 'the chief sensory nucleus of V and caudally with the dorsal horn. It receives pain, temperature, and tactile fibers from the face by way of the spinal tract of V. Axons from cells in this nucleus cross the midline and ascend in the ventral secondary ascending tract of V to terminate in nucleus ventralis posteromedialis of the dorsal thalamus. Syn: nucleus of the descending tract of V; spinal nucleus of V.

nucleus, spinal trigeminal see nucleus of the spinal tract of V.

nucleus, spinal vestibular see nucleus, inferior vestibular.

nucleus spinothalamicus cells of origin for the lateral and ventral spinothalamic tracts, in the dorsal funicular gray of the dorsal horn of spinal cord.

nucleus of Staderini see nucleus intercalatus [medulla].

nucleus, Stilling's column of nerve cells rostral to [and sometimes caudal to] and continuous with the dorsal nucleus of Clarke.

nucleus, sublingual see nucleus of Roller.

nucleus subputaminal [of Ayala] lateral portion of the substriatal gray.

nucleus, subthalamic nucleus of the ventral thalamus of the diencephalon, and serving as an important way station in the extrapyramidal system. Syn: body of Luys; corpus Luysi; nucleus of Luys.

nucleus, superior central tegmental nucleus located on either side of the midline of the midportion of the tegmentum in the pontine isthmus. It may be a part of the respiratory area.

nucleus, superior olivary nucleus in the caudal and ventral portion of the pontine tegmentum. It is related to the auditory system. Syn: dorsal nucleus of the trapezoid body. nucleus, superior salivatory parasympathetic nucleus located in the caudal part of the pontine tegmentum, medial to fasciculus solitarius and rostral to the inferior salivatory nucleus. It is composed of small cells supplying preganglionic fibers by way of the intermediate division of the facial nerve to the pterygopalatine ganglion for relay to the nasal, palatine, and lacrimal glands and to the submandibular and Langley's ganglia for relay to the sublingual and submandibular glands.

nucleus, superior sensory see nucleus, chief sensory, of V.

nucleus, superior vestibular nucleus located in the dorsolateral tegmentum of the pons at the level of the abducens nucleus. Its main connections include afferent fibers from the superior and posterior semicircular ducts and efferent fibers to the oculomotor and trochlear nuclei through the homolateral medial longitudinal fasciculus, vestibulocerebellar connections to the flocculonodular lobe, and both fastigial nuclei. Syn: nucleus of Bechterew.

nucleus, supraoptic [hypothalamus] nucleus consisting of large, deeply staining cells located over the lateral border of the optic tract. The cells elaborate neurosecretory material, particularly vasopressin, an antidiuretic hormone which is carried to the neurohypophysis along the hypothalamohypophysial [supraopticohypophysial] tract.

nucleus, supraspinal rostral extension of the ventromedial nucleus from the spinal cord into the caudal portion of the medulla,

nucleus, supratrochlear dorsal nucleus of the raphe in the periaqueductal gray at the level of the inferior colliculus.

nucleus tangentialis scattered nerve cells along the lateral border of the lateral vestibular nucleus and rostral end of the inferior vestibular nucleus.

nucleus tecti see nucleus, fastigial.

nucleus tegmenti any one of various nuclei in the tegmentum of the brain stem, sometimes particularly the red nucleus.

nucleus, thoracic see nucleus, dorsal, of Clarke.

nucleus, triangular vestibular see nucleus, medial vestibular.

nucleus, trochlear group of somatic motor cells in the dorsal, caudal part of the midbrain tegmentum. Its fibers spiral dorsally and caudally around the periaqueductal gray, cross the midline, and emerge from the dorsal surface of the brain stem at the junction of pons and midbrain as the major portion of the trochlear nerve, to supply the superior oblique muscle of the eye. Syn: motor nucleus of IV.

nucleus, unspecific thalamic see nucleus, nonspecific thalamic.

nucleus of the vagal nerve, dorsal see nucleus, dorsal efferent.

nucleus of the vagal nerve, ventral see nucleus ambiguus.

nucleus, ventral [dorsal thalamus] group of nuclei of the dorsal thalamus whose main subdivisions are nucleus ventralis anterior, nucleus ventralis lateralis, and nucleus ventralis posterior. They lie between the internal and external medullary laminae and extend almost the entire length of the dorsal thalamus ventral to the lateral thalamic nuclear group.

nucleus, ventral accessory olivary see nucleus, medial accessory olivary nucleus, ventral arcuate see nucleus, arcuate [medulla].

nucleus, ventral cochlear special somatic sensory nucleus located ventral or ventrolateral to the inferior cerebellar peduncle in the region of the pontomedullary junction. Its cells, larger than those in the dorsal cochlear nucleus, receive cochlear nerve fibers and send their axons mostly across the midline as trapezoid fibers to enter the lateral lemniscus and to end mainly in the inferior colliculus and partly in the medial geniculate nucleus.

nucleus, ventral, of fasciculus solitarius see nucleus parasolitarius.

nucleus, ventral motor see nucleus ambiguus.

nucleus, ventral, of the posterior commissure see nucleus of Darkschewitsch.

nucleus, ventral sensory see nucleus parasolitarius.

nucleus ventralis anterior [dorsal thalamus] nucleus of the ventral group located in the anterior part of the diencephalon lateral to the anterior nuclear group. Its main afferent fibers, from the globus pallidus by way of the thalamic fasciculus, convey impulses from the cerebral cortex [area 4s] and from other subcortical nuclei [e.g., subthalamic nucleus, substantia nigra]. It is concerned with the stabilization of cortically initiated movement through thalamocortical connections to area 4 and particularly to area 6. It may also serve as a relay center for diffuse thalamocortical projection. Syn: anterior ventral nucleus.

nucleus ventralis lateralis [dorsal thalamus] nucleus of the ventral group located in the dorsolateral pan of the dorsal thalamus between the internal and external medullary laminae. Its anterior portion is bounded rostrally and medially by nucleus ventralis anterior. More caudally it is lateral to the dorsomedial nucleus and dorsal to nucleus ventralis posterior. Posteriorly it is replaced by nucleus lateralis posterior. Its main afferent connections are from the contralateral cerebellum by way of dentothalamic and rubrothalamic fibers. Thalamocortical fibers from this nucleus go mainly to area 4 but also to area 6. Syn: lateral ventral nucleus.

nucleus ventralis posterior [dorsal thalamus] largest nucleus of the ventral group, it occupies the caudal half of the dorsal thalamus. It is located lateral to the dorsomedial and centromedian nuclei, ventral to nuclei ventralis lateralis and lateralis dorsalis, and posteriorly it is replaced by the pulvinar. It is divided into two portions, nucleus ventralis posteromedialis and nucleus ventralis posterolateralis. Syn: posterior ventral nucleus; ventrobasal nucleus.

nucleus ventralis posterior pars lateralis see nucleus ventralis posterolateralis.

nucleus ventralis posterior pars medialis see nucleus ventralis posteromedialis.

nucleus ventralis posterolateralis [dorsal thalamus] larger division of nucleus ventralis posterior located between the medial portion, nucleus ventralis posteromedialis, and the external medullary lamina. Fibers of the medial lemniscus and the lateral and ventral spinothalamic tracts terminate in this nucleus, from which thalamocortical fibers [sensory radiations] carry sensory impulses to the postcentral gyrus. Syn: nucleus ventralis posterior pars lateralis; posterolateral ventral nucleus.

nucleus ventralis posteromedialis [dorsal thalamus] subdivision of nucleus ventralis posterior. located between nucleus ventralis posterolateralis laterally and the dorsomedial and centromedian nuclei medially. The dorsal and ventral secondary ascending tracts of V and taste fibers of the medial lemniscus end in this nucleus for relay of sensory impulses by way of sensory radiations to the face area of the postcentral gyrus, just above the lateral fissure. Syn: nucleus ventralis pars medialis; nucleus posteromedialis ventralis; arcuate nucleus; posteromedial ventral nucleus; semilunar nucleus.

nucleus, ventrobasal [dorsal thalamus] see nucleus ventralis posterior.

nucleus ventrocaudalis [dorsal thalamus] posterior part of nucleus ventralis posterior.

nucleus ventrocaudalis externus [dorsal thalamus] posterior part of nucleus ventralis posterolateralis.

nucleus ventrocaudalis internus [dorsal thalamus] posterior part of nucleus ventralis posteromedialis.

nucleus ventrointermedius [dorsal thalamus] anterior part of posterior part of nucleus ventralis posterior

nucleus, ventrolateral [cord] column of nerve cells in the ventral part of the lateral division of the ventral horn in the cervical and lumbosacral enlargements. Fibers from these cells are thought to innervate the muscles of the shoulder girdle and upper arm and the hip and thigh. Syn: anterolateral nucleus.

nucleus, ventrolateral tegmental see nucleus, lateroventral tegmental.

nucleus, ventromedial [cord] column of nerve cells in the medial division of the ventral horn at most levels of the spinal cord. Fibers from these cell bodies are thought to supply neck, trunk, intercostal, and abdominal muscles. Syn: anteromedial nucleus.

nucleus, ventromedial [hypothalamus] nucleus located rostral and dorsal to the mammillary body. Its main afferent connections are from the septal area and anterior perforated substance [medial forebrain bundle], orbital cortex [orbitohypothalamic fibers], temporal lobe [stria terminalis and perhaps fornix], and globus pallidus [pallidohypothalamic fibers]. It discharges mainly through hypothalamotegmental fibers to the midbrain and appears to be related to food intake, regulation of autonomic nervous system and emotional expression.

nucleus ventrooralis externus [dorsal thalamus] ventrolateral part of nucleus ventralis lateralis.

nucleus ventrooralis internus [dorsal thalamus] ventromedial part of nucleus ventralis lateralis.

nucleus vestibularis magnocellularis see nucleus, lateral vestibular.

nucleus of Waldeyer see gray, dorsal funicular.

Nuel, J. P. [1847‑1920] Belgian physiologist and otologist. Nuel’s space is located between the outer pillar and the outer hair cells of the organ of Corti.

nystagmus oscillating movements of the eye, usually involuntary, and which may be normal or abnormal.

nystagmus, cerebellar nystagmus resulting from a cerebellar lesion, usually involving the pyramids or the fastigial nucleus.

nystagmus, horizontal nystagmus in which the eyes move in a horizontal plane.

nystagmus, jerk nystagmus in which there is a slow movement of the eyes in one direction and a quick return.

nystagmus, miner's nystagmus which is thought to be induced by poor illumination or poor vision.

Nystagmus, optokinetic nystagmus induced by viewing a succession of moving objects. Syn: railroad nystagmus.

nystagmus, palatal see myoclonus, palatal.

nystagmus, pendular nystagmus in which the oscillatory movements of the eyes are approximately equal in rate for the two directions.

nystagmus, railroad see nystagmus, optokinetic.

nystagmus, vertical nystagmus in which the eyes move in a vertical plane.

nystagmus, vestibular nystagmus resulting from stimulation or irritation of the vestibular portion of the internal ear, the vestibular nuclei or their related tracts.

o

Obersteiner-Redlich space or area segment of a nerve root in the subarachnoid space between the brain or spinal cord and the place of transition from glia to neurolemma.

obex [L. bolt, barrier] point on the mid‑dorsal surface of the medulla ovelying the caudal tip of the fourth ventricle where the teniae choroideae of the fourth ventricle meet.

oblongata see medulla oblongata.

oblongatal see medullar.

occipital pertaining to the occipital lobe or its cortex.

oculomotor [L. oculus—eye] see nerve and nucleus, oculomotor. olfactory [L. o1facere—to smell] pertaining to the sense of smell. Oligodendria see oligodendroglia.

oligodendroglia [Gr. oligos—scanty; dendron—tree; glia—glue] neuroglial cells of ectodermal origin, with small oval nuclei and fine cytoplasmic processes, located near nerve cell bodies and along nerve fibers throughout the central nervous system. They are thought to correspond to the satellite cells and neurolemma of the peripheral nervous system. Syn: oligoglia; oligodendria.

oligoglia see oligodendroglia.

oliva [N.A.] see olive.

olive protuberance on the ventrolateral surface of the medulla overlying the inferior olivary nucleus. Syn: oliva; inferior olive.

olive, dorsal accessory see nucleus, dorsal accessory olivary. olive, inferior see olive; nucleus, inferior olivary.

olive, medial accessory see nucleus, medial accessory olivary.

olive, principal see nucleus, inferior olivary.

olive, superior see nucleus, superior olivary.

onion‑skin pattern see pattern, onion‑skin.

Opalski cell see cell, Opalski.

operculum /o“per’ku“-lum/ [L. lid] part of the cerebrum which overlies the insula and which forms the lateral fissure.

operculum, frontal part of the frontal lobe which overlies the insula.

operculum, parietal part of the parietal lobe which overlies the insula.

operculum, temporal part of the temporal lobe which overlies the insula.

ophthalmoplegia external paralysis of the extraocular eye muscles.

ophthalmoplegia, internal paralysis of the ciliary muscle and constrictor muscle of the pupil of the eye.

ophthalmoplegia internuclear inability to turn the eye medially past the midposition of the eye on horizontal conjugate gaze. It occurs with a lesion of the medial longitudinal fasciculus between the levels of the motor nuclei of VI and III.

optic pertaining to the eye. For optic canal; chiasm; disc; foramen; papilla; nerve; radiation; tectum; thalamus; tract, see the nouns.

ora serrata scalloped outer edge of the ciliary body, marking its junction with the retina.

organ of Corti end organ for hearing, located on the basilar membrane in the cochlear duct of the internal ear. Syn: papilla or pars basilaris; spiral organ.

organ, Golgi tendon see spindle, neurotendinous.

organ, pineal see body, pineal.

organ, spiral see organ of Corti.

organ, subcommissural plate of modified ependyma, consisting of tall, columnar, ciliated cells, neurosecretory in function, in the cerebral aqueduct just caudal to the posterior commissure. It appears to play a significant role in water intake.

organ, vomeronasal specialized epithelial cells lining a pocket in the nasal septum, from which the vorneronasal nerve arises.

orthodromic [Gr. orthos—straight; dromus—running conducting in the normal or conventional direction.

orthosympathetic see sympathetic, 1.

ossicles three small bones present in the middle ear and which convey vibrations set up in the tympanic membrane to the oval window of the inner ear, viz., malleus, incus, and stapes.

otic pertaining to the car. For otic duct; fluid; ganglion; sac; and vesicle, see the nouns.

otoconia see otolith[s].

otocyst see vesicle, otic.

otolite see otolith[s].

otolith[s] small calcareous bodies embedded in the gelatinous otolithic membrane overlying the macula utriculi and macula sacculi in the internal ear. Syn: ear dust; statoconia; statolith.

oxytocin neurohypophysial hormone which acts on smooth muscle. Under certain conditions it stimulates contraction of uterine muscle and of the myoepithelial cells of the mammary gland. It is produced by cells of the paraventricular nucleus of the hypothalamus, transported by axoplasmic flow along the fibers of the paraventriculohypophysial tract to the neurohypophysis, where it is released. Syn: pitocin.

p

Pacchioni, Antonio [1665‑1726] Italian anatomist who described the enlarged arachnoid granulations in the superior sagittal sinus [Pacchionian bodies] in 1705. Pacchioni’s foramen is the incisure of the tentorium.

pachymeninx see dura mater.

Pacini, Filippo [1812‑1883] Italian anatomist. Pacinian corpuscles were first described by Vater, and later [1830] rediscovered and described by Pacini. see corpuscle, Pacinian,

pain, referred pain originating in a visceral organ but felt in a somatic area innervated by the same segment of the central nervous system.

paleocerebellum old portion of the cerebellum, comprising the vermis and the flocculi.

paleoolive dorsal and medial accessory olivary nuclei and the medial portion of the inferior olivary nucleus.

paleopallium pyriform lobe cortex and its underlying white matter; uncus and adjacent part of the parahippocampal gyrus.

paleostriatum see globus pallidus.

pallidum [L. pallidus—pale] see globus pallidus.

pallium [L. cloak] cerebral cortex and its underlying white matter.

palsy, Bell's idiopathic facial paralysis, often occurring after exposure to cold and thought to result from ischemia of the facial nerve.

palsy, bulbar weakness or paralysis of muscles supplied by a cranial nerve, after injury to the cell bodies or fibers of the lower motor neurons which supply them.

palsy, cerebral any type of neurologic disorder resulting from damage to the nervous system in utero, at birth, or early in life.

palsy, ocular paralysis or weakness of one or more of the extrinsic muscles of the eyeball.

palsy, pseudobulbar weakness or paralysis of muscles supplied by a cranial nerve after injury to the pyramidal tract fibers [upper motor neuron] which supply the cranial nerve motor nucleus of the involved muscles.

papilla basilaris see organ of Corti.

papilla, optic slight elevation on the retina where the optic nerve fibers leave the eye.

paraflocculus, dorsal [Gr. para—beside] biventer of the cerebellum [Larsell].

paraflocculus, ventral homologue in subprimate brains for the tonsil of the cerebellum [Larsell].

paraganglia see bodies, chromaffin.

parakoniocortex Brodmann's areas 42 and probably 52.

parallel fiber see fiber, parallel.

paralysis, alternate see hemiplegia, alternate.

paralysis, crossed see hemiplegia, crossed.

paralysis, flaccid paralysis in which the affected muscles receive too few nervous impulses and are atonic, as following injury to a motor nerve.

paralysis, spastic paralysis resulting from injury to the pyramidal and other associated tracts, and accompanied by spasticity of the affected muscles.

paraphysis cerebri midline telencephalic structure arising from the roof of the third ventricle at the junction of the telencephalon and diencephalon. It is well developed in some submammalian forms. It is present in the human embryo but normally disappears by 3.5 months prenatal age. Occasionally it persists and develops into a cystic tumor.

paraplegia paralysis of both lower extremities or, rarely, paralysis of both upper extremities.

parasolitary pertaining to the cellular area adjacent to fasciculus solitarius, i.e., to nucleus parasolitarius or parasolitary gray.

parastriate pertaining to occipital lobe cortex area 18, adjacent to the visual or striate cortex.

parasympathetic pertaining to that division of the autonomic nervous system, whose preganglionic neurons arise in the brain and in the sacral portion of the spinal cord. It is concerned with the maintenance of the body; the craniosacral subdivision of the autonomic nervous system.

parasympathetic afferent pertaining to the general visceral afferent fibers which accompany the fibers of the parasympathetic [motor] division of the autonomic nervous system.

parasympathetic, spinal postulated two‑neuron chain for peripheral vasodilatation. The first neuron has; its cell body in the spinal cord and its axon leaves the cord through the dorsal root to synapse in the dorsal root ganglion. The second neuron has its cell body in the dorsal root ganglion and its axon goes to blood vessels at the periphery of the body.

paraterminal area or body see area, paraterminal.

paresthesia abnormal spontaneous sensation, such as tingling.

parietal pertaining to the parietal lobe or its cortex.

Parkinson, James [1755‑1824] English physician who first described the syndrome of paralysis agitans [Parkinson's disease] in 1817.

parolfactory area see area, parolfactory.

pars basilaris see organ of Corti.

parvocellular composed of small cells.

pathway, final common motor neuron which receives impulses from multiple sources and carries impulses to voluntary, striated muscle; lower motor neuron.

pattern, onion‑skin pattern by which fibers carrying pain from the face descend in the spinal tract of V and end in the nucleus of the spinal tract of V, so that those from the region around the lips end in the closed medulla and those from the outer parts of the face end at successively caudal levels as far as the fourth cervical spinal cord segment.

Pavlov, Ivan Petrovich [1849‑1936] Russian physiologist noted for his experiments on conditioned reflexes.

peduncle [L. little foot] large band of nerve fibers in the brain, usually composed of more than one tract. Syn: brachium.

peduncle, anterior thalamic anterior thalamic radiations as they pass through the anterior limb of the internal capsule and corona radiata.

peduncle, cerebral 1. ventral portion of each half of the midbrain, consisting of rnidbrain tegmentum dorsally and basis pedunculi ventrally. 2. sometimes loosely used as a synonym for pes pedunculi.

peduncle of the corpus callosum see gyrus, subcallosal.

peduncle of the flocculus band of nerve fibers connecting the flocculus and the nodule of the cerebellum.

peduncle, inferior cerebellar bundle of nerve fibers joining the medulla and cerebellum and interconnecting the cerebellum with the vestibular complex, inferior olive, and reticular gray, and also containing fibers of the dorsal spinocerebellar, cuneatocerebellar, arcuatocerebellar, and cerebellomotorius tracts. Syn: restiform body; corpus restiforme.

peduncle of the inferior colliculus see brachium of the inferior colliculus.

peduncle, inferior thalamic 1. fibers in the sublenticular pan of the internal capsule and in the corona radiata, connecting the medial geniculate nucleus and possibly inferior colliculus with the temporal lobe cortex. 2. fibers in the anterior limb of the internal capsule and corona radiata connecting the dorsomedial thalamic nucleus and the orbital cortex and amygdala.

peduncle, middle cerebellar bundle of nerve fibers joining the pons and cerebellum and composed mostly of fibers of the pontocerebellar tract. Syn: brachium pontis.

peduncle, posterior thalamic fibers in the posterior part of the internal capsule and corona radiata which interconnect the cortex of the parietal and occipital lobes with the lateral thalamic nuclei, pulvinar, and superior colliculus.

peduncle, superior cerebellar bundle of nerve fibers joining the cerebellum and midbrain and composed mostly of fibers of the dentorubral and dentothalamic tracts. Syn: brachium conjunctivum.

peduncle, superior olivary fibers which arise from cells in the superior olive or the adjoining gray and which pass dorsomedially toward the abducens nucleus. Some fibers may continue as efferent fibers into the cochlear nerve,

peduncle, superior thalamic sensory radiations in the internal capsule and corona radiata connecting the ventral nuclear complex of the dorsal thalamus with the cortex of the frontal and parietal lobes.

pedunculus corporis callosi see gyrus, subcallosal.

periaqueductal [Gr. peri—around] around the cerebral aqueduct.

perilymph fluid contained in the spaces of the periotic labyrinth, surrounding the membranous labyrinth of the internal ear. Syn: liquor cotunnii, periotic fluid.

perikaryon [Gr. kary—nucleus] cytoplasm of a nerve cell body; sometimes used as a synonym for nerve cell body.

periotic fluid see perilymph.

perineurium the dense connective tissue which surrounds each fascicle of a nerve.

peripheral nervous system the nerves and ganglia.

peristriate pertaining to occipital lobe cortex area 19, anterior and adjacent to the parastriate area.

Perlia, R. [19th century] German ophthalmologist. The nucleus of Perlia is the central nucleus of the oculomotor nerve.

perseveration repetition of a word or other response, at first correctly, then in such a way that it is no longer relevant or appropriate.

pes hippocampi [L. pes—foot] anterior part of the hippocampus, marked on its ventricular surface by shallow grooves which give it the appearance of a paw.

pes pedunculi fibrous portion of the basis pedunculi of the midbrain, composed of pyramidal and corticopontine tracts.

‑petal suffix denoting afferent conduction to the region indicated.

photoreceptor light‑sensitive [rod] or color‑sensitive [cone] cell of the retina.

phrenic [Gr. phren—‑diaphragm] see nerve and nucleus, phrenic.

pia‑arachnoid [L. pius—tender] see leptomeninges.

pia mater [L. pius—tender; mater—mother] layer of the leptomeninges, which adheres to the surface of the brain and spinal cord and conforms to all the irregularities on their surfaces. Syn: intima pia.

PICA see artery, posterior inferior cerebellar.

Piccolomini, Archangelo [1526‑1605] Italian anatomist. see fiber[s] of Piccolomini.

Pick, Arnold [1851‑1924] Czechoslovakian psychiatrist. see bundle, Pick's.

pillar of the fornix, anterior portion of the fornix extending from the body of the fornix, anterior to the interventricular foramen and posterior to the anterior commissure, into the diencephalon to end mainly in the mammillary body. Syn: postcommissural fornix. Syn: column of the fornix.

pillar of the fornix, posterior posterior portion of the fornix between and continuous with the fimbria of the hippocampus and the body of the fornix. Syn: pillar of the fornix.

pineal body [L. pinea—pine cone] see body, pineal.

pinealocyte parenchymatous cell of the pineal body. These cells have long processes and knoblike endings, and are arranged in cords or clusters in a bed of neuroglia.

piriform [L. pear‑shaped] see area, pyriform.

pitocin see oxytocin.

planum temporale triangular area on the superior surface of the temporal lobe within the lateral fissure, located between the transverse temporal gyri [of Heschl] and the posterior margin of the Sylvian fossa.

plate, alar that portion of the mantle layer of the neural tube dorsal or dorsolateral to the sulcus lirnitans. Syn: dorsal plate.

plate, basal that portion of the mantle layer of the neural tube ventral or medial to the sulcus limitans. Syn: ventral plate.

plate, cribriform 1. thin, horizontal plate of the ethmoid bone through the perforations of which [olfactory foramina] the olfactory fila enter the cranial cavity. 2. see lamina cribrosa, 1.

plate, dorsal see plate, alar.

plate, Goor thin ventral wall of the neural tube.

plate, lateral thickened side‑wall of the neural tube, the mantle layer of which consists of an alar and a basal plate.

plate, neural thickening of the ectoderm along the mid‑dorsal surface of

embryo from which the neural tube is derived. plate, quadrigeminal see tectum.

plate, roof thin, mid‑dorsal membrane of the neural tube, from which the tela choroidea of the third ventricle and the anterior and posterior medullary velum of the fourth ventricle develop.

plate, ventral see plate, basal. plexus [L. something woven, a braid] 1. a network of nerve fibers or nerve filaments. Bundles of the peripheral nervous system. 2. a network of blood vessels.

plexus, Auerbach's see plexus, myenteric.

plexus, brachial nerve plexus derived from the ventral primary rami of spinal nerves C₅‑T₁, from which the nerves that supply the upper extremity arise

plexus, cervical plexus derived from the ventral primary rami of spinal nerves C₁-C₄. Its main branches include the phrenic nerve, motor branches to prevertebral and infrahyoid muscles of the neck, and cutaneous branches to part of the neck and head.

plexus, choroid [chorioid] 1. the secretory epithelium and associated blood vessels of the lateral, third, and fourth ventricles, which produce cerebrospinal fluid. The blood vessels associated with the secretory epithelium of the ventricles.

plexus, Cruveilhier’s plexus formed by the dorsal rami of the first three cervical spinal nerves.

plexus, Jacobson’s see plexus, tympanic.

plexus, Meissner’s see plexus, submucosal.

plexus, myenteric plexus of visceral afferent and efferent nerve fibers and bodies of parasympathetic postganglionic neurons between the circular and longitudinal layers of smooth muscle in the gastrointestinal tract. Syn: Auerbach's plexus.

plexus, solar [L. sol—sun] celiac plexus.

plexus, submucosal plexus of visceral afferent and efferent nerve fibers and bodies of parasympathetic postganglionic neurons in the submucosal layer of gastrointestinal tract. Syn: Meissner's plexus.

plexus, tympanic plexus of sensory fibers from the mucosal fining of the middle, and preganglionic parasympathetic fibers of the glossopharyngeal nerve, which enter the lesser petrosal nerve.

pocket, Rathke’s see Rathke, M. H.

point, Sylvian posterior point of the Sylvian triangle, at the posterior limit of lateral fissure. [Taveras and Wood, 1964]

point, upper Rolandic upper tip of the central sulcus on the medial surface of the cerebrum.

pole, frontal anterior tip of the frontal lobe of the cerebrum.

pole, occipital posterior tip of the occipital lobe of the cerebrum.

pole, temporal anterior tip of the temporal lobe of the cerebrum,

pons [L. bridge] 1. metencephalic subdivision of the brain stem, between

midbrain and the open medulla. 2. transverse fiber bundles visible on the ventral surface of the pontine portion of the brain stem, which connect this region and the contralateral cerebellar hemisphere.

pontile see pontine.

pontine pertaining to the pons.

pontocerebellum portion of the cerebellum which receives impulses derived mainly from the cerebral cortex and relayed to the cerebellum from the pons by way of the pontocerebellar fibers. Syn: neocerebellum.

porus acusticus externus opening of the external auditory meatus on the outside of the skull.

porus acusticus internus opening of the internal auditory meatus in the posterior cranial fossa.

postcentral posterior to 1. the central sulcus of the cerebrum; 2. the central lobule of the cerebellar vermis.

postcommissural posterior to the anterior commissure.

posterior commissure see commissure, posterior,

postganglionic pertaining to a neuron or part of a neuron whose cell body is located in an autonomic ganglion and whose axon terminates in relation to smooth muscle, cardiac muscle, or a gland.

postroland posterior to the central sulcus of the cerebrum. Syn: postcentral.

pouch, Rathke’s see Rathke, M. H.

precentral anterior to 1. the central sulcus of the cerebrum; 2. the central lobule of the cerebellar vermis.

precommissural /pre-com-mish’u'-ral/ anterior to the anterior commissure.

preculmen subdivision of the cerebellar vermis between the lingula and the culmen. Syn: central.

precuneus segment of the parietal lobe on the medial surface of the cerebrum, anterior to the parietooccipital fissure. Syn: quadrate lobule.

prefrontal pertaining to the prefrontal area of the frontal lobe.

preganglionic pertaining to a neuron or part of a neuron whose cell body is located within the central nervous system and whose axon synapses in an autonomic ganglion.

premotor pertaining to the premotor area of the frontal lobe.

preoccipital cortex see area, peristriate.

preoptic pertaining to the region immediately anterior to the optic chiasm. see area and recess, preoptic.

prepyriform see area, prepyriform.

prerolandic anterior to the central sulcus of the cerebrum. Syn: precentral.

presubiculum area of transition between the subiculum and the entorhinal cortex; Brodmann's area 27.

pretectum see area, pretectal.

pretrigeminal pertaining to the region rostral to the motor and chief sensory nuclei of V, particularly the pontine isthmus.

Probst see bundle and tract of Probst. For commissure of Probst, see commissure of the lateral lemniscus.

process filamentous extension of a nerve cell body, which may be either an axon or a dendrite.

process, protoplasmic thick, short, rough process of a multipolar nerve cell body; a dendrite, similar in structure to the cytoplasm of the cell body.

projection fibers see fibers, projection.

prominence, spiral ridge on the spiral ligament in the cochlear duct, between the stria vascularis and the cells of Claudius of the organ of Corti.

proprioceptive pertaining to impulses originating within the body, especially from muscles, tendons, and joints, and the vestibular portions of the internal ear.

propriospinal limited to or contained within the spinal cord.

prosencephalon most rostral subdivision of the three‑vesicle brain and its derivatives; anlage of the forebrain.

prothalamus rostral one third of the preopticohypothalamic area, containing the preoptic and anterior hypothalamic area and separated from the remainder of the hypothalamus by the fornix.

protoneuron first neuron in a reflex arc.

protopathic pertaining to the appreciation of gross pain, tactile, and temperature sensations.

psalterium see lyra [of David].

pseudounipolar neuron see neuron, unipolar.

pterygopalatine ganglion see ganglion, pterygopalatine.

ptosis /to“'' sis/ drooping of the upper eyelid.

pulvinar [L. pulvinus—pillow] posterior portion of the dorsal thalamus, which projects into the subarachnoid space.

pupil circular aperture in the center of the iris, which by changes in its diameter regulates the amount of light admitted to the eye.

pupil, Argyll Robertson miotic pupil that does not react to light but constricts upon convergence‑accommodation.

Purkinje, Johannes Evangelista [1787‑1869] Bohemian physiologist. He described the Purkinje cells of the cerebellum in 1837 and also named the fibers in the sinoatrial node.

putamen /pu“-ta’men/ [L. shell] lateral portion of the lentiform nucleus, compose mostly of small and medium‑sized cells. One of the basal ganglia, it underlies the insula, and is continuous anteriorly with the head of the caudate nucleus.

pyramid 1. protuberance on the ventral surface of the medulla, through which run the pyramidal tract. 2. see pyraramis. 3. pyramidal cell. 4. petrous portion of the temporal bone.

pyramid, Ammon's double pyramid of the cornu ammonis.

pyramid, double elongated neuron of the cornu ammonis having a rich dendritic process at each end. Its axon arises from the cell body or one dendrite and enter the alveus and fimbria.

pyramid, posterior old term for fasciculus gracilis.

pyramis lobule of the posterior lobe of the cerebellar vermis, between the uvula and the tuber. Syn: pyramid.

pyriform [piriform] [L. pear—shaped] see area, pyriform.

q

quadrangular lobule anterior or posterior crescentic lobule of the cerebellar hemisphere.

quadrantanopsis [quadrantanopsia] blindness in one quarter of the visual field.

quadrate lobule see precuneus.

quadrigeminal body see colliculus, superior and inferior.

quadrigeminal plate see tectum.

r

radiation, acoustic see radiation, auditory radiation

radiation, anterior thalamic nerve fibers which pass through the anterior limb of the internal capsule, interconnecting the anterior and dorsomedial nucleus of the dorsal thalamus with the cingulate and prefrontal cortices.

radiation, auditory nerve fibers which pass through the sublenticular portion of the posterior limb of the internal capsule, carrying auditory impulses from the medial geniculate nucleus to the transverse temporal gyri. Syn: geniculotemporal tract. radiation, frontal see forceps, anterior. radiation, occipital see forceps, posterior. radiation, olfactory, of Zuckerkandl see band, diagonal, of Broca.

radiation, optic nerve fibers of the visual system from the lateral geniculate nucleus through the posterior limb of the internal capsule to the visual cortex in the occipital lobe. Syn: geniculocalcarine tract.

radiation, posterior thalamic nerve fibers in the postlenticular portion of the posterior limb of the internal capsule including fibers of the corticotectal, corticotegmental, corticorubral, and corticonigral tracts from the occipital lobe cortex to the pulvinar and to various brain stem nuclei.

radiation, sensory nerve fibers which pass through the thalamolenticular portion of the internal capsule from the ventral nucleus of the dorsal thalamus, mostly to areas 3, 1, and 2 of the postcentral gyrus, but also to certain other areas including area 4 of the precentral gyrus.

radiation, tegmental fibers which extend upward on the lateral surface of the red nucleus. radiation, thalamic thalamocortical and corticothalamic fibers in the internal capsule and corona radiata.

Ramón y Cajal, Santiago [1852‑1934] Spanish histologist and Nobel co-laureate with C. Golgi [1906] noted for his contributions to the histology and pathology of the nervous system.

ramus anastomoticus [L. ramus—branch] [B.N.A.] see ramus communicans.

ramus, anterior ascending branch of the lateral fissure which separates the triangular from the opercular portion of the inferior frontal gyrus.

ramus, anterior horizontal branch of the lateral fissure which separates the orbital from the triangular portion of the inferior frontal gyrus.

ramus communicans [N.A.] small branch interconnecting the ventral primary ramus of a spinal nerve with the sympathetic trunk of the same side. Syn: ramus anastomoticus.

ramus, dorsal primary dorsal division of the spinal nerve, innervating the genuine muscles of the back and the overlying cutaneous area.

ramus, fizz a handy libation for those evenings spent poring over neuroanatomy texts.

ramus, gray ramus communicans composed largely of unmyelinated postganglionic fibers whose cell bodies are located in the ganglia of the sympathetic trunk and which terminate in visceral structures underlying or associated with the skin.

ramus, ventral primary ventral division of a spinal nerve innervating the musculature of the extremities and of the trunk [other than the genuine muscles of the back] and the associated cutaneous areas.

ramus, white ramus communicans composed mostly of myelinated preganglionic fibers whose cell bodies are located in the thoracolumbar spinal cord and which terminate in chain or collateral sympathetic ganglia.

Ranvier, Louis Antoine [1835‑1922] French histologist who described the nodes of Ranvier in 1878.

raphé /ra“’’fe/ [Gr. rhaphe—seam] intersection of fibers along the midline of the pons and medulla.

Rathke, M.H. [1793‑1860] anatomist of Konigsberg. Rathke's pouch is a dorsal, midline epithelial pocket in the stomodeal ectoderm, from which the anterior lobe of the pituitary gland develops. It forms a closed, double‑layered sac which loses its connection with the stomodeum. The thin posterior wall of the sac fuses with the infundibulum and becomes the pars intermedia of the anterior lobe. The anterior wall thickens to form the pars distalis. Extensions upward onto the infundibular stalk become the pars tuberalis. Although the lumen of the sac is retained in some forms, it nearly or completely disappears in man.

recess, fastigium see fastigium.

recess, infrapineal that portion of the superior subarachnoid cistern between the pineal body and the superior colliculi.

recess, infundibular extension of the third ventricle ventrally into the infundibular stalk between the optic chiasm and the mammillary bodies.

recess, lateral lateral conical portion of the fourth ventricle.

recess, optic see recess, preoptic.

recess, pineal posterior portion of the third ventricle, just anterior to the pineal body and between the habenular and posterior commissures.

recess, preoptic that portion of the third ventricle superior and anterior to the optic chiasm. Syn: optic recess; supraoptic recess.

recess, supraoptic see recess, preoptic.

recess, suprapineal posterior extension of the third ventricle above the pineal body and between the two habenulae.

recessus tecti see fastigium.

referred pain see pain, referred.

reflex automatic stereotyped response to a stimulus dependent upon an intact connection between a sensory and a motor neuron.

reflex, Achilles plantar flexion of the foot by contraction of the muscles of the calf of the leg, on percussion of the Achilles tendon just above the calcaneus. It is dependent on afferent and efferent connections of the first and second sacral and possibly the fifth lumbar spinal cord segments, mainly S1. Syn: triceps surae reflex; gastrocnemius reflex; ankle jerk.

reflex, axon local vasodilatation restricted to an area of cutaneous stimulation, a reflex thought to be dependent on the terminal portions of peripheral nerve fibers.

reflex, Babinski extension of the great toe in response to stroking the sole of the foot, after injury to the pyramidal tract,

reflex, biceps flexion at the elbow by contraction of the biceps muscle on percussion of the biceps tendon, dependent on afferent and efferent connections of the fifth and sixth cervical spinal cord segments.

reflex, blink closure of the eyes in response to a bright light or sudden visual stimulus. It is dependent on afferent connections from the retina through the optic nerve with relay to the visual cortex, then to the pons for efferent connections through the facial nerve.

reflex, brachioradialis flexion at the elbow and supination of the hand by contraction of the brachioradialis muscle on percussion of the tendon of insertion of the brachioradialis, or of its tendon of origin, or along the lower one‑third of the lateral surface of the radius. It is dependent on afferent and efferent connections of the fifth and sixth cervical spinal cord segments. Syn: radial periosteal reflex.

reflex bundle see fasciculus proprius.

reflex, ciliospinal dilation of the pupils in response to pain, usually from the region of the head or upper part of the body, mediated through connections involving the superior colliculus, lateral tectotegmentospinal tract, preganglionic sympathetic fibers from the upper thoracic cord, and postganglionic fibers from the superior cervical ganglion.

reflex, consensual light constriction of the pupil in response to stimulation by light of the retina of the opposite eye.

reflex, corneal closure of the eyes on stimulation of the cornea. It is dependent on afferent connections through the ophthalmic division of the trigeminal nerve and efferent connections through the facial nerve in the pons.

reflex, cremasteric elevation of the scrotum on stroking the skin on the inner side of the thigh, dependent on afferent and efferent connections of the first and second lumbar spinal cord segments.

reflex, crossed reflex in which a stimulus applied to one side of the body produces a contralateral response,

reflex, deep motor response to stimulation of sensory endings in muscle, tendon and joints.

reflex, deltoid abduction of the upper arm by contraction of the deltoid muscle on percussion of the insertion of the deltoid muscle, dependent on afferent and efferent connections of the fifth and sixth cervical spinal cord segments.

reflex, direct light light reflex in which the response occurs in the same eye as stimulated.

reflex, gag contraction of the pharyngeal musculature in response to stimulation of the pharyngeal mucosa or of the fauces. It is dependent on afferent connections through the glossopharyngeal nerve and efferent connections through the vagus nerve in the medulla. Syn: pharyngeal reflex.

reflex, gastrocnemius see reflex, Achilles.

reflex[es], Hering‑Breuer reflexes increasing the rate and decreasing the depth of breathing and arising from pulmonary vagal receptors activated by inflation and/or deflation of the lungs.

reflex, light constriction of the pupil in response to light striking the retina.

reflex, myotatic see reflex, stretch.

reflex, oculocardiac slowing of the heart, lowering of the blood pressure, and modification of the respiratory rhythm in response to compression of the eyeballs. It is dependent on afferent [pain] fibers in the trigeminal nerve and efferent fibers in the vagus nerve.

reflex, patella stretch reflex involving extension at the knee by contraction of the quadriceps femoris muscle on percussion of the patellar tendon. It is dependent on afferent and efferent connections of the second through fourth lumbar spinal cord segments. Syn: knee jerk; quadriceps reflex.

reflex, pharyngeal see reflex, gag.

reflex, quadriceps see reflex, patellar.

reflex, radial periosteal see reflex, brachioradialis.

reflex, segmental reflex in which a stimulus, applied in the region of the sensory distribution of a spinal nerve, produces a response in muscles innervated by the same spinal cord segment.

reflex, stapedial contraction of the stapedial muscle of the middle ear by way of facial nerve fibers, in response to excessive auditory impulses transmitted by the cochlear nerve. It serves to dampen the effects of loud sounds.

reflex, stretch contraction of a muscle in response to its being stretched. It involves a two‑neuron chain in which the afferent neuron, whose peripheral termination is in a muscle spindle, synapses directly on a motor neuron. Syn: myotatic reflex. See also reflex, tendon.

reflex, superficial motor response to stimulation of sensory endings in the skin.

reflex, tendon reflex contraction of a muscle, elicited by a sharp tap on its tendon; the receptor on the afferent limb of the reflex is, however, in the muscle itself and not in the tendon proper.

reflex, triceps extension at the elbow by contraction of the triceps muscle on percussion of the biceps tendon, dependent on afferent and efferent connections of the sixth through the eighth cervical spinal cord segments [C₆‑C₈].

reflex, biceps surae see reflex, Achilles.

Reff, Johann Christian [1759‑1813] German physician. He first noted the insula [island of Red] in 1796 and described it in 1809. Reil's ansa is the ansa peduncularis. The ribbon of Reil is the medial lemniscus.

Reissner, Ernst [1824‑1878] German anatomist who described the vestibular membrane of the cochlea [Reissner's membrane] in 1851.

releasing factors—substances produced in the median eminence and tuberal region of the hypothalamus. They are conveyed by nerve fibers and released into the hypophysial portal sinusoids for activation of anterior pituitary hormones.

Remak, Robert [1815‑1865] German neurologist who wrote the first account of the myelin sheath [ 1836] and identified unmyelinated nerve fibers [fibers of Remak] in 1838.

reservoir see cistern.

restiform body see peduncle, inferior cerebellar.

reticular formation see formation, reticular.

retina inner layer of the eyeball, between the choroid on its outer surface and the vitreous body which it encloses. It develops from the optic cup and contains the sensory portion of the eye. Its layers, beginning with the outermost, next to the choroid, are as follows:

layer 1 pigment layer‑single layer of pigmented, cuboidal cells which develops from the outer layer of the optic cup.

nervous layer all the layers of the retina, exclusive of the pigment layer, which develop from the inner layer of the optic cup.

layer 2 Layer of rods and cones‑layer comprising the rod‑shaped and cone-shaped dendritic processes of the photoreceptors. Syn: bacillary layer.

layer 3 outer limiting membrane‑layer composed of the terminal processes of the Müller cells, through which the rods and cones are connected to their cell bodies. Syn: external limiting membrane.

layer 4 outer nuclear layer‑layer comprising the cell bodies of the rod and cone cells. Syn: external nuclear layer; outer granular layer.

layer 5 outer plexiform layer‑synaptic layer containing the axons of the rods and cones and the dendrites of the bipolar cells, as well as the dendrites of the horizontal cells. Syn: outer molecular or reticular layer.

layer 6 inner nuclear layer‑layer containing the cell bodies of the bipolar cells, the second link in the chain of retinal connections; also the nuclei of the Müller cells, which are supporting cells and neuroglial in type, and the cell bodies of horizontal and amacrine cells, which are retinal association neurons. Syn: inner granular layer; outer ganglionic layer.

layer 7 Inner plexiform layer‑synaptic layer containing the axons of the bipolar cells and dendrites of the ganglion cells, as well as the axons of the amacrine cells. Syn: * inner molecular or reticular layer.

layer 8 ganglion cell layer‑layer containing the large cell bodies, the third link in the chain of retinal connections, whose axons compose the optic nerve.

layer 9 optic nerve fiber layer‑layer composed of the axons of the ganglion cells which turn and run under the inner surface of the retina to the optic disc, where they leave the eyeball as the optic nerve. Retinal arteries and veins are also in this layer. Syn: stratum opticum.

layer 10 inner limiting membrane‑delicate membrane composed of terminal processes of Müller’s cells, on the inner surface of the retina.

retrosubicular posterior to the subiculum of the hippocampal formation.

Rexed layers subdivisions of the gray matter of the spinal cord, described for cat but characteristic of other forms as well [Rexed, 1964]. There are ten layers arranged roughly, from dorsal to ventral, as follows:

lamina I layer of cells of various sizes applied to the surface of substantia gelatinosa. Syn: layer of marginal cells; Waldeyer’s layer.

lamina II layer of closely packed cells, which caps the dorsal horn. Syn: substantia gelatinosa.

lamina III layer of cells somewhat larger and less densely arranged than those in lamina II. It lies ventral to and within the concavity of lamina II. It corresponds to the dorsal portion of nucleus proprius.

lamina IV layer of cells of various sizes, loosely arranged in the dorsal horn, ventral to lamina III. This layer contains many myelinated fibers. It corresponds to the ventral portion of nucleus proprius. Lamina I‑IV correspond to the head of the dorsal horn.

lamina V relatively thick layer in the neck of the dorsal horn. The medial two‑thirds is paler than the lateral third and contains more cells of smaller size. The lateral portion, cut through by fiber bundles, is the reticular area of the spinal cord.

lamina VI fairly broad layer at the base of the dorsal horn, prominent only in the enlargements. Its smaller medial portion contains smaller, more closely packed cells than the lateral part. The medial and lateral divisions of this layer correspond approximately to Cajal’s internal and external basal nuclei.

lamina VII layer that occupies most of the intermediate zone between the dorsal and ventral horns and, at appropriate levels, includes the dorsal nucleus of Clarke, the intermediolateral nucleus [lateral horn] and intermediomedial nucleus. In the enlargements it extends ventrally into the lateral part of the ventral horn, where it surrounds the lateral cell groups of lamina IX.

lamina VIII layer that extends across the base and maid‑portion of the thoracic ventral horn, but in the enlargements it is confined to the medial half. It surrounds the medial cell groups of lamina IX.

lamina IX ventral horn cell groups, the axons from which enter the ventral roots.

lamina X small area of gray matter around the central canal, consisting mainly of the dorsal and ventral gray commissures. Syn: central gray.

rheobase minimum current intensity necessary to excite when allowed to flow for an indefinitely long period.

rhinenphalon certain parts of the cerebrum, mainly on its basal surface, including the olfactory bulb and stalk, anterior olfactory nucleus, anterior perforated substance, olfactory gyri, parolfactory area, diagonal band and its nucleus, hippocampus. parahippocampal gyrus, and uncus. It corresponds to the limbic lobe, but usually excluding the cingulate gyrus and isthmus of the fornicate gyrus.

rhinal lobe see rhinencephalon.

rhodopsin purple‑red pigment present in rods and important in maintaining the sensitivity of the rod system in twilight or night vision. It consists of retinine [an aldehyde form of vitamin A] and opsin, a protein. It is broken down by fight and restored in the dark. Syn: visual purple.

rhombencephalon [Gr. rhombus‑rhomb or lozenge; enkephalos—brain] most caudal subdivision of the three‑vesicle embryonic brain; the anlage of the hindbrain, from which the medulla, pons, and cerebellum develop.

rhombic lip see lip, rhombic.

rhomboid fossa floor of the fourth ventricle.

rigidity, decerebrate extensor posture in which all four limbs are stiffly extended. The arms are internally rotated at the shoulders, extended at the elbows, and hyperpronated. The fingers are extended at the interphalangeal joints all [flexed at the interphalangeal joints]. The legs are extended at the hips, knees and ankles, and the toes are plantar flexed.

rigidity, extrapyramidal increased resistance to passive movement, usually with cogwheel jerks but without the clasp‑knife phenomenon characteristic o spasticity.

Robertson, Argyll see Argyll Robertson, Douglas; pupil, Argyll Robertson.

Robin, C. P. [1821‑1885] physician and histologist in Paris. He described in greater detail the spaces around brain blood vessels, previously noted by Virchow.

rod light‑sensitive photoreceptor of the retina. see also cone.

rodlet elongated straight or crescent‑shaped intranuclear organoid of nerve cells visible in fixed and in living material.

Rolando, Luigi [1773‑1831] Italian anatomist. He described the central sulcus o the cerebrum in his lectures at the University of Turin and in 1839 Francçois Leuret named it the fissure of Rolando in his honor. Rolando’s lobe is the operculum. see also substantia gelatinosa [of Rolando]; vein, Rolandic.

Roller, Christian Friedrich Wilhelm [1802‑1878] German neurologist. see nucleus of Roller.

Romberg, Moritz Heinrich [1795‑1873] German neurologist. Romberg’s sign described in 1840, consists of increased difficulty in balancing while standing after closing the eyes, due to a loss of position sensibility.

roof nucleus see nucleus, fastigial,

root, anterior see root, ventral.

root, dorsal bundle of afferent nerve fibers whose cell bodies are located in a spinal ganglion and which enter the dorsolateral surface of the spinal cord. Syn: posterior root.

root, mesencephalic, of V bundle of nerve fibers located in the pontine isthmus ventrolateral to the fourth ventricle and in the midbrain lateral to the periaqueductal gray. It consists of the single processes of unipolar cells in the mesencephalic nucleus of V. These fibers bifurcate as they leave the root. One branch, a dendrite, carries impulses from proprioceptive endings mainly in the muscles of mastication, partly in some or all of the extraocular eye muscles. The other branch, an axon, terminates mainly in the motor nucleus of V, or motor nuclei of the nerves supplying the extraocular eye muscles. Syn: mesencephalic tract of V.

root, nerve intramedullary portion of a cranial nerve.

root, posterior see root, dorsal.

root of Roller descending fibers of the vestibular root.

root, ventral bundle of efferent nerve fibers arising from the ventrolateral portion of the spinal cord and joining a dorsal root to form a spinal nerve. Syn: anterior root.

rootlet, dorsal one of the fascicles which combine to form the dorsal root of a spinal nerve.

rootlet, ventral spinal nerve one of the fascicles which combine to form the ventral root of a nerve.

Rosenthal, Friedrich Christian [1780‑1829] German anatomist who described the basal vein [Rosenthal's vein].

rosette, cerebellar axonal termination of a mossy fiber in contact with the clawlike dendritic terminate on of granule cells in a cerebellar island of the granular layer of the cerebellar cortex.

rostrum, corpus callosum portion of the corpus callosum between the genu and the lamina rostralis.

rudiment, hippocampal see induseum griseum.

Ruffini, Angelo [1874‑1929] Italian anatomist who described certain sensory nerve endings [Ruffini endings or corpuscles] in 1898.

Russell's fasciculus see fasciculus, uncinate, 1.

sac, endolymphatic dilated terminal portion of the endolymphatic duct, located within the dura mater on the posterior surface of the petrous part of the temporal bone.

sac, otic see sac, endolymphatic.

saccule somewhat spherical subdivision of the membranous labyrinth, located in front of the utricle in the vestibule of the bony labyrinth. It is connected with the utricle by the utriculosaccular duct and with the cochlear duct by the ductus reuniens.

sagulum, nucleus group of elongated triangular auditory cells, irregularly distributed along the external surface of the lateral lemniscus at levels between the trochlear nucleus and trochlear decussation.

saltatory conduction see conduction, saltatory.

sand, brain calcareous bodies in the pineal body. Syn: acervulus.

satellite cell see cell[s], satellite.

satellite nucleolus see nucleolus, satellite.

Sattler's layer vascular lamina of the choroid of the eye.

scala media see duct, cochlear.

scala tympani perilymphatic space of the bony labyrinth of the cochlea, separated from the cochlear duct by the basilar membrane and organ of Corti.

scala vestibuli perilymphatic space of the bony labyrinth of the cochlea, separated from the cochlear duct by the vestibular membrane.

Scarpa, Antonio [1747‑1832] Italian anatomist who described the vestibular ganglion [Scarpa's ganglion] in 1779. Scarpa's nerve is the nasopalatine nerve.

Schlemm, Friedrich [1795‑1858] German anatomist who described the canal of Schlemm in 1830, although it had been noted by Fontana in 1778.

Schmidt, Henry D. [1823‑1888] American anatomist. see incisure of Schmidt-Lantermann.

Schultze, Maximillian Johann Sigismund [1825‑1874] German anatomist who described fasciculus interfascicularis [tract of Schultze].

Schütz, fasciculus of see fasciculus, dorsal longitudinal.

Schwalbe, Gustav A. [1844‑19161 German anatomist who described the medial vestibular nucleus [nucleus of Schwalbe].

Schwann, F. Theodor [1810‑1882] German anatomist who described the neurolemma [sheath of Schwann] in 1839

sclera dense, white, fibrous, connective tissue which constitutes the external tunic of the eyeball.

sector, Sommer’s subdivision of the cornu ammonis, beneath the ventricular surface and opposite the hippocampal fissure, in which the pyramidal cells appear to be especially sensitive to oxygen deficiency. ‑

segment, internodal portion of a myelinated nerve fiber between two nodes of Ranvier.

segment, spinal cord block of spinal cord from which all the root fibers of a given pair of spinal nerves arise.

segment, sympathetic that point of the sympathetic trunk from which a specific gray ramus arises, whether or not this point is marked by a ganglion.

sella turcica [L. sella—saddle; turcica—Turkish] saddle‑shaped depression in the sphenoid bone, which contains the pituitary gland.

sensory decussation see decussation, sensory.

septum, dorsal median [L. septum—fence] connective tissue septum extending ventrally between the two dorsal funiculi, from the mid‑dorsal surface of the spinal cord and closed medulla to the gray matter.

septum lucidum see septum pellucidum.

septum pellucidum [pellucidum from L. peer—through; lucere—to shine] thin sheet of tissue between the corpus callosum and the fornix and forming most of the medial wall of the anterior horn of the lateral ventricle.

septum, postcommissural see septum pellucidum.

septum posticum see septum, subarachnoid.

septum, precommissural see area, parolfactory.

septum, subarachnoid incomplete membranous attachment of the pia mater to the arachnoid along the mid‑dorsal line of the spinal cord. Syn: septum posticum.

serotonin [5‑dihydroxytryptaminel a neurotransmitter occurring in the raphé nuclei of the brain stem. Although regarded as a synaptic transmitter, its exact role is obscure.

sheath, axial inner layer of the double‑layered connective tissue capsule of neuromuscular and neurotendinous spindles.

sheath, Henle’s delicate mesodermal connective tissue investment of individual peripheral nerve fibers. Syn: endoneurium; epilemma; sheath of Key and Retzius; Ruffini’s subsidiary sheath.

sheath of Key and Retzius see Henle's sheath.

sheath, Mauthner’s see axolemma.

sheath, myelin white, fatty sheath surrounding the neuraxis of many central and peripheral nerve fibers.

sheath, neurolemmal see neurolemma.

sheath, nucleated see neurolemma.

sheath, primitive see neurolemma.

sheath, Ruffini’s subsidiary see endoneurium.

sheath of Schwann see neurolemma,

shepherd’s crook see crook. shepherd's.

Sherrington, Sir Charles Scott [1857‑1952] English physiologist and Nobel laureate who made many contributions in the field of neurophysiology.

sign, Babinski see reflex, Babinski.

sign, Bárány’s nystagmus following injection of warm or cold water into the external auditory meatus and varying with pathology of the internal ear.

sign, segmental clinical manifestation indicative of a lesion at a particular level the central nervous system.

sign, tract clinical manifestation indicative of injury to a central nervous system tract.

sinus, cavernous paired dural sinus located on the lateral surface of the body of sphenoid bone. It consists of many venous channels which receive blood primarily from the ophthalmic vein, sphenoparietal sinus, the superficial middle cerebral vein, and several emissary veins. It is connected with its contralateral counterpart by way of the intercavernous sinuses, and is drained by the superior and inferior petrosal sinuses.

sinus, circular anterior and posterior intercavernous sinuses.

sinus, dural any of the valveless venous channels located along the attachments of the dural folds or in the free edges of the folds.

sinus, endolymphatic expanded portion of the endolymphatic: duct with which the utricular and saccular ducts communicate.

sinus of Gibbs see sinus, tentorial.

sinus, inferior longitudinal see sinus, inferior sagittal.

sinus, inferior petrosal paired dural venous sinus which connects the cavernous sinus with the internal jugular vein along the junction of the petrous portion the temporal bone and the basal portion of the occipital bone to the jugular foramen.

sinus, inferior sagittal dural sinus within the free edge of the falx cerebri, extending backward to the junction of the falx and tentorium cerebelli, to empty into the straight sinus. Syn: inferior longitudinal sinus.

sinus, jugular see bulb, jugular.

sinus, lateral see sinus, transverse.

sinus, occipital small dural sinus along the midline in the attachment of the falx cerebelli and connecting veins of the internal vertebral plexus and the confluence sinuum.

sinus, sigmoid paired dural venous sinus which, as a continuation of the transverse sinus, forms an S‑curve from the occipitopetrosal junction down to the jugular foramen.

sinus, sphenoparietal paired dural sinus located along the posterior edge of the lesser wing of the sphenoid bone. It empties into the cavernous sinus.

sinus, straight midline dural sinus along the attachment of the falx cerebri to the tentorium cerebelli. It is formed by the union of the inferior sagittal sinus and the great cerebral vein and empties usually into the left transverse sinus.

sinus, superior longitudinal see sinus, superior sagittal.

sinus, superior petrosal dural sinus along the anterior attachment of the tentorium cerebelli on the crest of the petrous portion of the temporal bone. It connects the cavernous sinus and the junction of the transverse and sigmoid sinuses.

sinus, superior sagittal dural sinus in the midline extending from the foramen cecum along the attachment of the falx cerebri to the internal occipital protuberance . It receives blood mainly from the superior cerebral veins, and usually empties into the right transverse sinus. Syn: superior longitudinal sinus.

sinus tentorial one relatively constant channel in a venous plexus in the tentorium cerebelli. It empties into the junction of the straight sinus and the transverse

sinus, transverse paired dural sinus along the bony attachment of the tentorium cerebelli from the inferior occipital protuberance to the posterolateral tip of the petrous portion of the temporal bone, The right sinus usually drains the superior sagittal sinus and the left the straight sinus. Each sinus also receives blood from the superficial veins of the occipital lobe and from the superior petrosal sinus and empties into the sigmoid sinus. Syn: lateral sinus.

sinus venous sclerae [N.A.] see canal of Schlemm.

siphon [syphon, carotid] series of bends in which the internal carotid artery runs forward in the cavernous sinus, turns upward on the inner side of the anterior clinoid, proms, pierces the dura, and enters the subarachnoid space, then courses backward below the optic nerve and turns upward lateral to the optic chiasm.

sleep paralysis disorder characterized by inability to move or cry out, taking place on going to sleep or awakening.

sieve, dural dural investment of each spinal nerve within the intervertebral space.

Soemmering’s substance see substantia nigra.

solar plexus celiac plexus.

soma [Gr. body] see body, cell.

somatic efferent pertaining to the nerve component consisting of fibers that conduct impulses from motor nuclei of the brain or spinal cord to striated muscles of somite origin. 11ow fibers from the brain are sometimes designated as special, and those from the spinal cord as general.

somesthetic pertaining to the general somatic senses, viz., somatic pain, temperature, tactile, vibratory, and position sensibility.

Sommer's sector see sector, Sommer's.

space, anterior perforated see substance, anterior perforated.

space, epidural space external to the dura mater of the spinal cord, containing many thin‑walled blood vessels and, particularly in its caudal portion, adipose tissue.

space[s] of Fontana spaces separated by fibers of the pectinate ligament at the corneoscleral junction. It is located between the anterior chamber of the eye and the canal of Schlemm and transports aqueous humor from the anterior chamber to the canal.

space of His space, perhaps a shrinkage artifact, between the external surface of vessels less Å and the footplates of the astrocytes in the brain and spinal cord. It surrounds vessels of smaller caliber than does the Virchow‑Robin space.

space, Meckel’s see cavern trigeminale.

space, periotic see labyrinth, periotic.

space, posterior perforated see substance, posterior perforated.

space, subarachnoid space between the arachnoid and the pia mater, containing cerebrospinal fluid, and through which pass the nerve roots and the blood vessels supplying the central nervous system.

space, subdural potential space between the dura mater and the arachnoid.

space[s], Virchow‑Robin perivascular spaces, around blood vessels entering the central nervous system in fixed sections of tissue.

spasmus nutans disorder of infants characterized by nystagmus, head movements and torticollis.

spasticity increased resistance to passive movement, with clasp‑knife character and overactive reflexes, due to an exaggeration of stretch reflexes. There is increased muscle tone in antigravity muscles [the extensor muscles of the lower extremities, and the flexor muscles of the upper extremities].

spatia anguli iridocornealis [N.A.] see spaces of Fontana.

special somatic afferent [SSA] pertaining to the nerve component consisting of fibers which conduct visual and auditory impulses from the retina and cochlea, respectively, [exteroceptive] and from the vestibular apparatus [proprioceptive] to the brain.

special somatic efferent [SSE] pertaining to the nerve component consisting of fibers which conduct impulses from motor nuclei of the bruin stem to the extraocular muscles of the eye and the muscles of the tongue, which in lower forms are derived from somites.

special visceral afferent [SVA] pertaining to the nerve component consisting of fibers which conduct olfactory and gustatory impulses from their sensory epithelium to the brain.

special visceral efferent [SVE] pertaining to the nerve component consisting of fibers which conduct impulses from motor nuclei to striated muscle of branchiomeric [visceral arch] origin.

spider cell old term for astrocyte.

spina bifida disorder characterized by failure in the closure of the spinal column due to a defect in the development of vertebrae, with or without an associated defect of the spinal meninges and spinal cord.

spina bifida occultis spina bifida which is limited to defective closure of the vertebra.

spinal parasympathetic see parasympathetic, spinal.

spindle, muscle sensory nerve ending in skeletal muscle, having a double‑walled connective tissue capsule and containing small muscle fibers, nerve fibers, and capillaries. It is thought to be stimulated when the muscle fibers are stretched, and to function partly in stretch reflexes.

spindle, neuromuscular see spindle, muscle.

spindle, neurotendinous sensory nerve ending in tendons, having a double‑walled connective tissue capsule and containing small tendon fibers. Syn: Golgi ending; Golgi tendon organ; Ib receptor.

spindle, tendon see spindle, neurotendinous.

spine[s], dendritic see gemmule[s].

spinocerebellum portion of the cerebellum which receives impulses predominantly from the spinal cord, mainly by way of the spinocerebellar and cuneatocerebellar tracts. Syn: paleocerebellum.

splanchic [Gr. splanchic—visceral] see nerve, splanchnic.

splenium [Gr. splenion—bandage] posterior portion of the corpus callosum.

split brain see brain, split.

spongioblast [Gr. spongio—sponge; blastos—germ] forerunner of a neuroglial cell.

SSA see special somatic afferent.

SSE see special somatic efferent.

Staderini, Rudolfo Italian anatomist who described nucleus intercalatus [nucleus of Staderini].

stalk, olfactory bundle of nerve fibers arising from the olfactory bulb and extending posteriorly across the ventral surface of the frontal lobe to divide into medial and lateral olfactory striae as it joins the overlying hemisphere. Syn: olfactory tract.

statoconia see otolithi[s].

statolith see otolith[s].

stem, brain axial portion of the brain exclusive of the cerebellum and the forebrain; the medulla, pons, and midbrain.

Stilling, Benedict [1810‑1879] German anatomist who described many features of the spinal cord. see nucleus, Stilling’s.

strabismus condition resulting from impaired function of an extraocular nerve or muscle so that one eye deviates and the two eyes do not focus on a single point. Syn: squint.

strabismus, external strabismus in which the affected eye deviates laterally.

strabismus, internal strabismus in which the affected eye deviates medially.

stratum [L. layer or blanket] see also lamina; layer. For the layers [strata] of the superior colliculus, see colliculus, superior.

stratum album one of the fibrous layers of the superior colliculus. see colliculus, superior.

stratum cinereum see colliculus, superior [stratum griseurn superficiale].

stratum, external sagittal see fasciculus, inferior longitudinal.

stratum griseum see colliculus, superior.

stratum lemnisci see colliculus, superior.

stratum opticum 1. see colliculus, superior. 2. optic nerve fiber layer of the retina.

stratum zonale see colliculus, superior.

stria [L. furrow] see also stripe; lamina.

stria Baillarger externa layer of nerve fibers in layer IV of the cerebral cortex.

stria Baillarger interna layer of nerve fibers in layer V of the cerebral cortex.

stria, cerebellar see stria medullaris of the fourth ventricle.

stria cornea see stria terminalis.

stria habenularis see stria. medullaris thalami.

stria, lateral olfactory olfactory tract fibers which arise from mitral cells in the olfactory bulb, course through the olfactory stalk, then turn laterally to end in the lateral olfactory area. Syn: lateral olfactory tract.

stria[e], longitudinal fiber strands continuous with the fimbria which accompany the induseum griseum over the corpus callosum, in the depth of the sulcus of the corpus callosum. Syn: medial and lateral white stripes of Lancisi.

stria, medial olfactory olfactory tract fibers which arise from mitral cells in the olfactory bulb, course through the olfactory stalk, then turn medially to end mostly in the medial olfactory area. Syn: medial olfactory tract.

stria medullaris acustici see stria medullaris of the fourth ventricle. stria medullaris of the fourth ventricle band of medullated fibers which crosses the floor of the fourth ventricle. The fibers arise mainly from cells in the arcuate nuclei adjacent to the pyramids, pass along the raphe of the medulla to the floor of the fourth ventricle. The fibers enter the inferior cerebellar peduncle to end in the cerebellum. Syn: cerebellar stria.

stria medullaris thalami bundle of fibers which runs from the interventricular foramen posteriorly along the dorsal and medial border of the thalamus to the habenula. It is composed, in part, of fibers from the fornix, stria terminalis, and medial forebrain bundle. Syn: stria habenularis; stria pinealis; stria pinealis see stria medullaris thalami.

stria terminalis nerve fiber bundle of the forebrain, which extends along the tail and body of the caudate nucleus, with connections primarily between two amygdala, and from the amygdala to the diencephalon. Syn: tenia semicircularis; stria cornea.

stria vascularis layer of epithelium which secretes endolymph in the cochlear duct on the side away from the modiolus.

stria, visual see stripe of Gennari.

striate marked with striae, especially pertaining to the visual cortex of the occipital lobe, which contains the stripe of Gennari.

striatum [L. striatus—furrowed] usually the caudate nucleus and putamen, sometimes including the globus pallidus.

strings, auditory component filaments of the basilar membrane which are tightly stretched between the tympanic lip of the limbus laminae spiralis and the crest the spiral ligament of the cochlea. Syn: basilar fibers.

stripe see also stria.

stripe of Gennari macroscopic layer of nerve fibers in layer IV of the visual cortex. It constitutes a well developed outer stripe of Baillarger in this region. Its fibers are the terminal portions of the optic radiations. Syn: visual stria.

stripe of Kaes layer of nerve fibers in layer II of the cerebral cortex. Syn: stripe Vicq d’Azyr, stripe of Kaes‑Bechterew.

stripe[s] of Lancisi see stria[e], longitudinal.

stripe, lateral white of Lancisi lateral strand of the longitudinal striae.

stripe, medial white of Lancisi medial strand of the longitudinal striae.

subcommissural organ see organ, subcommissural.

subdural between the dura mater and the arachnoid; often a site of hemorrhage.

subiculum four‑layered cortex of the hippocampal formation, continuous with the cornu ammonis. It is located in the dorsal portion of the parahippocampal gyrus adjoining the hippocampal fissure.

submucosal plexus see plexus, submucosal.

subnucleus caudalis caudalmost subdivision of the nucleus of the spinal tract of V. It resembles the dorsal horn in appearance.

subnucleus interpolaris middle subdivision of the nucleus of the spinal tract of V, located approximately at the level of the middle third of the inferior olive.

subnucleus rostralis most rostral subdivision of the nucleus of the spinal tract of V at upper medullar and pontine levels.

substance, anterior perforated area between the medial and lateral olfactory striae, posterior to the olfactory trigone, and lateral to the optic tract. Syn: anterior perforated space, or area olfactoria; olfactory area.

substance, chromidial see granules, Nissl.

substance, Nissl see granules, Nissl

substance, posterior perforated area between the two bases pedunculorum of the midbrain and posterior to the mammillary bodies, through which many small blood vessels, including the thalamoperforating arteries and the median arteries of the brain stem, enter the midbrain tegmentum. Syn: posterior perforated space.

substance, Rolando's gelatinous see substantia gelatinosa.

substance, transmitter see neurotransmitter.

substantia alba [N.A.] white matter of the central nervous system.

substantia ferriginea pigmented cells of locus ceruleus.

substantia gelatinosa [N.A.] [of Rolandi] nucleus composed of small, closely packed cells in the outer portion of the dorsal horn throughout the spinal cord and continuous with the nucleus of the spinal tract of V of the medulla.

substantia grisea gray matter of the central nervous system.

substantia innominata [of Reichert] medial portion of the substriatal gray , ventral to the globus pallidus. Its connections are similar to those of the globus pallidus. Syn: ganglion or basal nucleus of Meynert.

substantia intermedia centralis [N.A.] gray matter surrounding‑the central canal of the spinal cord.

substantia intermedia lateralis [N.A.] gray matter of the spinal cord, continuous medially with the substantia intermedia centralis, and extending laterally between the ventral and dorsal horns. Syn: lateral horn.

substantia nigra nucleus of pigmented nerve cells in the basis pedunculi of the midbrain and in the caudal part of the ventral thalamus. Syn: Soemmering's substance.

subthalamus see thalamus, ventral.

sulcomarginal fasciculus see fasciculus, sulcomarginal.

sulcus [L. groove or furrow] also fissure. Groove on the surface of the brain or spinal cord.

sulcus, anterior parolfactory small sulcus on the medial surface of the frontal lobe, marking the anterior boundary of the parolfactory area.

sulcus, anterolateral see sulcus, ventrolateral.

sulcus, basilar midline groove on the ventral surface of the pons, for the basilar artery.

sulcus, calcarine see fissure, calcarine.

sulcus, callosal see sulcus of the corpus callosum.

sulcus, callosomarginal see sulcus, cingulate.

sulcus, central 1. sulcus about midway between the frontal and occipital poles and which separates the frontal and parietal lobes. Its upper end extends a short distance onto the medial surface of the hemisphere. On the lateral surface it extends anteriorly and inferiorly to a point just above, but not joining, the lateral fissure. Syn: fissure of Rolando. 2. sulcus on the surface of the insula which separates the short gyri anterosuperiorly from the long gyri posteroinferiorly.

sulcus, cingulate sulcus on the medial surface of the cerebrum, separating the cingulate from the superior frontal gyrus and from the paracentral and the superior parietal lobules. Syn: callosomarginal or subfrontal sulcus.

sulcus, circular sulcus at the margin of the insula, at the line of reflection between the insula and the overlying opercula. Syn: sulcus limitans insulae.

sulcus, collateral sulcus between the parahippocampal and the fusiform gyri. Syn: fourth temporal sulcus.

sulcus of the corpus callosum sulcus separating the corpus callosum from the adjoining cingulate gyrus.

sulcus, dorsal intermediate sulcus on each side of the dorsal surface of the closed medulla and upper spinal cord and separating the gracile fasciculus and tubercle from the cuneate fasciculus and tubercle.

sulcus, dorsal median shallow sulcus on the mid‑dorsal surface of the closed medulla and spinal cord. Syn: posteromedian sulcus.

sulcus, dorsolateral shallow sulcus on the dorsolateral surface of the spinal cord along the line of attachments of the dorsal roots, and extending rostrally onto the medulla. Syn: posterolateral sulcus.

sulcus, external spiral groove in the cochlear duct between the spiral prominence and the organ of Corti.

sulcus, fourth temporal see sulcus, collateral.

sulcus, hemispheric shallow circular furrow which separates the telencephalon from the diencephalon of the developing brain.

sulcus, hypothalamic sulcus on the wall of the third ventricle extending from the interventricular foramen to the cerebral aqueduct and separating the dorsal thalamus dorsally from the hypothalamus ventrally.

sulcus, inferior frontal sulcus on the lateral surface of the frontal lobe, which separates the middle frontal gyrus above it from the inferior frontal gyrus below it.

sulcus, inferior pontine sulcus on the ventral surface of the brain stem under the lowest crossing fibers of the pons, marking the boundary between the medulla oblongata and the pons.

sulcus, inferior temporal sulcus on the ventral [inferior] surface of the temporal lobe, which separates the inferior temporal gyrus lateral to it from the fusiform gyrus medial to it. Syn: occipitotemporal sulcus; third temporal sulcus.

sulcus, internal spiral groove in the cochlear duct between the vestibular and tympanic lips of the limbus laminae spiralis.

sulcus, intraparietal sulcus on the lateral surface of the parietal lobe, which separates the superior parietal lobule above it from the inferior parietal lobule below it. Syn: Turner's sulcus.

sulcus, lateral mesencephalic sulcus on the lateral surface of the midbrain, which separates the tegmentum from the base of the cerebral peduncle.

sulcus, lateral occipital horizontally placed sulcus on the lateral surface of the occipital lobe. It separates the somewhat variable lateral occipital gyri into a superior and an inferior group.

sulcus limitans shallow groove on the lateral wall on either side of the neural canal, indicating the boundary between the alar and basal plates. This sulcus is retained in the adult brain as a groove on the floor of the fourth ventricle marking the medial border of the vestibular area.

sulcus limitans insulae see sulcus, circular.

sulcus, marginal branch of the cingulate sulcus separating the paracentral from the superior parietal lobule on the medial surface of the cerebrum.

sulcus, median midline sulcus on the floor of the fourth ventricle separating the two halves of the rhomboid fossa.

sulcus, middle frontal inconstant sulcus which, in some brains, subdivides the middle frontal gyrus into superior and inferior portions.

sulcus, middle temporal sulcus on the lateral surface of the temporal lobe, which separates the middle temporal gyrus above it from the inferior temporal gyrus below it. Syn: second temporal sulcus.

sulcus, occipitoparietal see fissure, parietooccipital.

sulcus, occipitotemporal see sulcus, inferior temporal.

sulcus, oculomotor sulcus medial to the base of the cerebral peduncle, from which the oculomotor nerve leaves the midbrain.

sulcus, olfactory sulcus on the ventral surface of the frontal lobe which separates the gyrus rectus medial to it from the orbital gyri lateral to it and along which the olfactory bulb and stalk are located.

sulcus, orbital several sulci in the form of an H or X on the ventral surface of the frontal lobe, which divide the orbital gyri into anterior, medial, posterior, and lateral portions.

sulcus, paracentral sulcus on the medial surface of the frontal lobe, separating the paracentral and superior frontal gyri.

sulcus, postcentral sulcus on the lateral surface of the parietal lobe, which roughly parallels the central sulcus and which separates the postcentral gyrus anterior to it from the superior and inferior parietal lobules posterior to it. Syn: postcentral fissure.

sulcus, posterior parolfactory sulcus separating the anterior and posterior paraolfactory gyri.

sulcus, posterolateral see sulcus, dorsolateral.

sulcus, posteromedian see sulcus, dorsal median.

sulcus, postolivary sulcus dorsal to the olive on the surface of the medulla.

sulcus, precentral sulcus on the lateral surface of the frontal lobe, which roughly parallels the central sulcus and which separates the precentral gyrus posterior to it from the superior, middle, and inferior frontal gyri anterior to it. Syn: precentral fissure.

sulcus, preolvary sulcus separating the olive and pyramid on the surface of the medulla and through which the rootlets of the hypoglossal nerve emerge.

sulcus, primary see fissure preclival.

sulcus, rhinal sulcus between the uncus and the anterior portion of the temporal lobe, and sometimes continuous with the collateral sulcus.

sulcus, scleral slight furrow around the cornea at the corneoscleral junction of the eye. Syn: sulcus sclerae.

sulcus scleral see sulcus, scleral.

sulcus, second temporal see sulcus, middle temporal.

sulcus, semicircular sulcus along the dorsolateral ventricular surface of the thalamus, separating the thalamus from the caudate nucleus lateral to it. The terminal vein and stria terminalis are located along this sulcus. Syn: terminal sulcus.

sulcus, subfrontal see sulcus, cingulate.

sulcus, superior frontal sulcus on the lateral surface of the temporal lobe, which separates the superior frontal gyrus above it from the middle frontal gyrus below it.

sulcus, superior pontine sulcus on the ventral surface of the brain stem above the uppermost crossing fibers of the pons, marking the boundary between the pons and midbrain.

sulcus, superior temporal sulcus on the lateral surface of the temporal lobe, which separates the superior temporal gyrus above it from the middle temporal gyrus below it.

sulcus, terminal see sulcus. semicircular.

sulcus, transverse temporal sulcus separating the two transverse temporal gyri of the superior surface of the temporal lobe, within the lateral fissure.

sulcus, Turner’s see sulcus, intraparietal.

sulcus, ventral median deep sulcus on the mid‑ventral surface of the medulla and spinal cord. Syn: ventral median fissure.

sulcus, ventrolateral sulcus on the surface of the medulla caudal to the olive, and continuous as a shallow and somewhat indistinct groove on the surface of the spinal cord along the line of emerging ventral roots. Syn: anterolateral sulcus.

superior colliculus see colliculus, superior.

suprasellar above the sella turcica.

supratentorial above the tentoriurn cerebelli.

SVA see special visceral afferent.

SVE see special visceral efferent.

Sydenham, Thomas [1624‑1689] English physician who first described many diseases including a chorea of children [Sydenham’s chorea].

Sylvian for Sylvian aqueduct, fissure; fossa; point; and triangle, see the nouns.

Sylvius, Francis de la Boe [1614‑1672] French anatomist who described the lateral fissure of the cerebrum in 1641 [fissure of Sylvius].

Sylvius, Jacobus [Jacques Dubois] [1478‑1555] French anatomist who described the cerebral aqueduct in 1555 [aqueduct of Sylvius].

sympathetic [Gr. syn—with; pathos—suffering] 1. pertaining to that division of the autonomic nervous system, whose preganglionic neurons arise in the thoracic and upper lumbar segments of the spinal cord; the thoracolurnbar subdivision of the autonomic nervous system. Syn: orthosympathetic. 2. old term for autonomic.

sympathetic afferent pertaining to the general visceral afferent fibers which accompany the fibers of the sympathetic [motor] division of the autonomic nervous system.

synapse [Gr. to clasp] region of communication between neurons, the point at which an impulse passes from the axon of one neuron to the dendrite or cell body of another; term coined by C.S. Sherrington.

syphon, carotid see siphon, carotid.

syringobulbia [Gr. syrinx—a tube] malformation in which there is cavitation usually slitlike rather than tubular] of the medulla and frequently associated with syringomyelia.

syringocele see canal, central.

syringomyelia [Gr. syrinx—a tube; myelos—marrow; hence spinal cord] malformation in which there is tubular cavitation of the spinal cord extending over many segments.

system, autonomic nervous that portion of the peripheral nervous system which provides the motor innervation for smooth muscle, cardiac muscle and glands, as they are concerned in metabolic activity. Syn: involuntary nervous system.

system, central nervous brain and spinal cord.

system, centrencepalic central core of brain tissue extending from the spinal cord through the reticular and tegmental portions of the brain stem to the diencephalon, and consisting of multisynaptic ascending and descending neuron chains. It is regarded by some as an integrating system related to arousal, facilitation, and suppression. Syn: reticular formation.

system, extrapyramidal a system of neurons, or a neuron chain, beginning in the cerebral cortex and terminating in motor nuclei of the brain stem and spinal cord, usually with synapses in the basal ganglia.

system, limbic limbic lobe and the subcortical nuclei, including parts of the hypothalamus, epithalamus, thalamus, and possibly midbrain, with which it is related anatomically and functionally.

system, peripheral the nerves and ganglia.

t

tactile pertaining to the sense of touch.

taenia [B.N.A.] see tenia.

tapetum [L. tapete—carpet or tapestry] fibers of the corpus callosum as they spread laterally, forming a roof over the inferior horn of the lateral ventricle.

Tarin, Pierre [ca. 1725‑1761] French anatomist who described the dentate gyrus [Tarin's fascia] and the interpeduncular fossa [fossa of Tarin].

Tawara, K. S. [1873‑1938] Japanese pathologist. The node of Tawara is the atrioventricular node.

tears, crocodile excess lacrimal secretion which occurs when salivary glands are stimulated during eating, in patients with faulty recovery from facial paralysis.

technique, Marchi see method, Marchi.

tectum [L. roof] roof of the midbrain, composed of the superior and inferior colliculi. Syn: quadrigeminal plate. see also corpora quadrigemina.

tectum, optic see colliculus, superior.

teeth, auditory, of Huschke small ridges on the surface of the limbus laminae spiralis overlying the vestibular lip.

tegmentum [L. cover] dorsal portion of the cerebral peduncle of the midbrain between the cerebral aqueduct and tectum dorsally and the basis pedunculi ventrally, and the dorsal portion of the pons between the fourth ventricle dorsally and the basis pontis ventrally.

Teil, isle of see insula.

tela choroidea [ L. teia—web] pia mater [and sometimes the ependyma with which it is fused, and the associated blood vessels] which forms a roof over the third and the caudal part of the fourth ventricle.

telencephalon [Gr. telos—end; enkephalos—brain] most rostral subdivision of the five‑vesicle embryonic brain; also the adult derivative of this subdivision. see also cerebrum.

telencephalon impar see telencephalon medium,

telencephalon medium that part of the telencephalon anterior to a plane from the base of the interventricular foramen to the upper border of the optic chiasm and adjacent to the anterior part of the third ventricle. It includes the preoptic area, lamina terminalis, and, where present, the paraphysis. Syn: telencephalon impar.

telodendron [G. telos—end; dendron—tree] terminal branching of a dendrite.

temporal pertaining to the temporal lobe or its cortex.

tendon organ, Golgi see spindle, neurotendinous.

tenia [N.A.] taenia [Gr. tainia—band or tape] 1. fine of attachment of the choroid plexus where a thin membrane merges with the substance of the brain. 2. band of nerve fibers.

tenia acustica see stria medullaris.

tenia choroidea [N.A.] line of attachment of the choroid plexus along the thalamus and stria, terminalis in the body and inferior horn of the lateral ventricle and along the junction of the posterior medullary velum with the medulla in the caudal part of the fourth ventricle.

tenia fimbriae [N.A.] line of attachment of the choroid plexus along the fimbria, in the inferior horn of the lateral ventricle.

tenia fornicis [N.A.] line of attachment of the choroid plexus along the fornix in the body of the lateral ventricle.

tenia semicircularis see stria terminalis.

tenia tectae see stripe of Lancisi.

tenia thalami [N.A.] line of attachment of the choroid plexus of the third ventricle along the stria medullaris of the thalamus.

Tenon's capsule fascia bulbi of the eye.

tentorium cerebelli [L. tentorium—tent] dural fold interposed between the cerebrum and the cerebellum and forming a roof over the posterior cranial fossa.

tetraplegia paralysis of all four extremities.

thalamencephal see diencephalon.

thalamencephalon see diencephalon.

thalamectomy operation in which a part of the dorsal thalamus is excised Syn: thalamotomy.

thalamocele [thalamocoele] third ventricle.

thalamus [Gr. thalamous—inner chamber] [B.N.A.] see thalamus, dorsal.

thalamus, dorsal subdivision of the diencephalon located on either side of the third ventricle, just dorsal to the hypothalamic sulcus. Some of its nuclei constitute important centers for the sensory systems.

thalamus optic see dorsal thalamus.

thalamus, ventral that part of the diencephalon located ventral to the dorsal thalamus and caudolateral to the hypothalamus, and consisting of the zona incerta and nucleus of the field of Forel, the entopeduncular nucleus, subthalamic nucleus, and the rostral continuations of the red nucleus and substantia nigra, which nuclei are way stations in the extrapyramidal system. Syn: subthalamus. The ventral thalamus is not to be confused with the ventral nuclei of the dorsal thalamus.

theca lenticularis [L. theca—a case or sheath] innermost layer of fine fibers of the external capsule, on the outer surface of the putamen.

tigroid granule [body] see granule, Nissl.

tinnitus ringing in the ears; head noises.

torcular Herophili [L. wine‑press of Herophilus] sinuses.

trabecula[-ae], arachnoid thin, filamentous strands interconnecting the arachnoid and the pia mater across the subarachnoid space.

tract bundle of nerve fibers within the central nervous system, usually having a common origin and a common termination. see also bundle; column; fasciculus; fibers.

tract, aberrant pyramidal see fiber[s], aberrant pyramidal.

tract, acousticooptic tract from the inferior colliculus top the superior colliculus.

tract, anterior corticospinal see tract, ventral corticospinal.

tract, anterior spinocerebellar see tract, ventral spinocerebellar.

tract, anuloolivary see tract, central tegmental.

tract, arcuatocerebellar fibers arising from cells in the arcuate nucleus of the medulla which pass by way of ventral superficial arcuate or stria medullaris fibers through the inferior cerebellar peduncle to the cerebellum.

tract, Arnold’s see tract, frontal corticopontine.

tract of Barnes uncrossed descending tract, in the superficial ventrolateral portion of the spinal cord, including olivospinal and pyramidal tract fibers.

tract, Burdach’s see fasciculus cuneatus.

tract, central tegmental fiber bundle located in the tegmentum of the brain stem. It consists of a descending chain of neurons from the basal ganglia [pallido-incerto-tegmento-rubro-olivary fibers] and connections from the cerebellum [dentato-olivary fibers] which end mainly in the inferior olivary nucleus, but it also includes fibers that end in the reticular gray, nucleus ambiguus, and, to some extent, the spinal cord [Bebin, 1956]. Syn: anulo-olivary or thalamo-olivary tract: medial tract of the tegmentum.

tract, central trigeminal see tract, ventral or dorsal secondary ascending, of V.

tract, cerebellomotorius see fibers, cerebellormotorius.

tract, cerebellospinal spinal portion of the uncinate fasciculus arising in the fastigial nucleus of the cerebellum and terminating in the cervical spinal cord.

tract, cerebrospinal see tract, corticospinal.

tract, comma see fasciculus interfascicularis.

tract, corticobulbar that part of the pyramidal tract which descends into and terminates in motor nuclei of the brain stem. Syn: corticonuclear tract.

tract, corticonuclear see tract. corticobulbar.

tract, corticorubral tract arising from cells mostly in the frontal cortex. The fibers descend through the posterior limb of the internal capsule and end, without crossing the midline, in the large‑celled portion of the red nucleus.

tract, corticospinal [direct] that part of the pyramidal tract which descends into and terminates in the spinal cord monosynaptically. Syn: cerebrospinal tract; present only in higher primates.

tract, corticospinal [indirect] that part of the pyramidal tract which descends into and terminates in the spinal cord disynaptically or through spinal interneurons; the only pathway to spinal motoneurons in rodents.

tract, crossed pyramidal see tract, lateral corticospinal.

tract, cuneatocerebellar tract arising from cells in the lateral cuneate nucleus, which passes by way of dorsal superficial arcuate fibers through the inferior cerebellar peduncle and terminates in the cerebellar vermis. Its fibers carry proprioceptive and tactile impulses from the homolateral upper extremity and neck.

tract, cuneocerebellar see tract, cuneatocerebellar.

tract, Deiterospinal see tract, ventrolateral vestibulospinal.

tract of Dejerine see tract, ventral spinothalamic.

tract, descending, of V see tract, spinal, of V.

tract, direct Cerebellar see tract, dorsal spinocerebellar.

tract, direct cerebrospinal see tract, ventral corticospinal.

tract, dorsal central trigeminal see tract, dorsal secondary ascending, of V.

tract, dorsal secondary ascending, of V tract arising from cells in the chief sensory

nucleus of V. Its fibers, some of which cross the midline in the pons, end bilaterally in nucleus ventralis posteromedialis of the dorsal thalamus. The tract carries impulses for fine tactile discrimination from the face. Syn: dorsal trigeminal lemniscus; dorsal central trigeminal tract.

tract, dorsal spinocerebellar uncrossed tract arising from the dorsal nucleus of Clarke and carrying proprioceptive and tactile impulses primarily from lower extremities to the cerebellar vermis, primarily to central, culmen, clivus, pyramis, and uvula. Syn: direct or posterior spinocerebellar tract; tract of Flechsig.

tract, dorsal tegmental dorsal longitudinal fasciculus.

tract of Flechsig see tract, dorsal spinocerebellar. 2. see fasciculus, septomarginal.

tract, flocculooculomotor tract arising from Purkinje cells in the flocculus of the cerebellum and terminating in the oculomotor nucleus of the midbrain, and concerned with the maintenance of tone in the ocular muscles.

tract, frontal corticopontine tract arising from cells in the cortex of the frontal lobe and terminating in the rostral and medial portions of the pontine gray. Syn: Arnold's tract; frontopontine tract.

tract, frontopontine see tract, frontal corticopontine.

tract, geniculocalcarine see radiation, optic.

tract geniculotemporal see radiation, auditory.

tract of Goll see fasciculus gracilis.

tract of Gowers see tract, ventral spinocerebellar.

tract, Gudden’s mammillotegmental tract.

tract, habenulointerpeduncular bundle of nerve fibers arising from the habenular nucleus of the epithalamus and terminating in the interpeduncular nucleus of the midbrain. Syn: fasciculus or tract of Meynert; fasciculus retroflexus; habenulointerpeduncular tract.

tract, Helweg’s see tract, olivospinal.

tract, hypothalamohypophysial tract consisting of supraopticohypophysial and paraventriculohypophysial fibers, which carry certain neurohypophysial hormones from cell bodies in the hypothalamic nuclei into the neurohypophysis where they are released.

tract, indirect cerebellar see tract, ventral spinocerebellar.

tract, lateral corticospinal that part of the corticospinal tract which crosses the midline in the motor decussation and descends in the lateral funiculus of the spinal cord. Syn: crossed or lateral pyramidal tract.

tract, lateral olfactory see stria, lateral olfactory.

tract, lateral pyramidal see tract, lateral corticospinal.

tract, lateral reticulospinal tract arising in the lateral and medial reticular gray of the medulla and perhaps other brain stem levels. It descends into the spinal cord in the lateral funiculus next to the gray matter between the dorsal and ventral horns. Some fibers end in the lateral horn [T₁ and T₂] and carry impulses for sweating of the homolateral side of the face, neck, and upper shoulder.

tract, lateral spinothalamic crossed tract composed of secondary neurons carrying pain and temperature from one side of the body to the nucleus ventralis posterolateralis of the contralateral dorsal thalamus.

tract, lateral vestibulospinal see tract, ventrolateral vestibulospinal.

tract, Lissauer’s see fasciculus, dorsolateral.

tract, medial olfactory see stria. medial olfactory.

tract, medial tectospinal tract composed of fibers which arise in the superior colliculus, enter the stratum album profundum, and curve around the periaqueductal gray. It crosses the midline in the dorsal tegmental decussation and turns caudalward in a position just ventrolateral to the medial longitudinal fasciculus to reach the cervical spinal cord. Its fibers end by way of intercalated neurons mainly on ventral horn cells which supply neck muscles, but also on cells which supply upper extremity muscles. Syn: predorsal fasciculus or bundle of Edinger.

tract, medial, of the tegmentum see tract, central tegmental.

tract, medial vestibular tract composed of fibers arising from cells in the homolateral and contralateral inferior, medial, and lateral vestibular nuclei; its fibers descend as a part of the medial longitudinal fasciculus into the dorsal part of the ventral funiculus of the spinal cord and end mainly on cells in the accessory nucleus of the cervical spinal cord, for positioning of the head.

tract, mesencephalic, of V see root, mesencephalic, of V.

tract of Meynert see tract, habenulointerpeduncular.

tract, Monakow’s see tract, rubrospinal.

tract, nigrostriate [-al] tract arising from cells in the substantia nigra. Its fibers pass rostralward and lateralward, interdigitate with fibers of the internal capsule, and release dopamine in the lentiform nucleus. Syn: comb bundle.

tract, occipital corticopontine tract said to arise from cells in the cortex of the occipital lobe and terminating in the pontine gray.

tract, occipitopontine see tract, occipital corticopontine.

tract, olfactory the olfactory stalk, or the fibers of the medial and lateral olfactory tracts [striae] which it contains.

tract, olivospinal tract composed of fibers which arise in the inferior olivary nucleus. Most fibers cross the midline at the level of their origin and descend along the ventrolateral border of the spinal cord to end on motor cells of the cervical spinal cord. Syn: Helweg's tract.

tract, optic bundle of nerve fibers of the visual system from the optic chiasm to the lateral geniculate nucleus.

tract, pallidohypothalamic tract said to arise from cells of the globus pallidus, mainly the medial segment, and end chiefly in the ventromedial nucleus of the hypothalamus, and to be a part of the discharge path for emotional expression.

tract, paraventriculohypophysial tract composed of fibers arising in the paraventricular nucleus of the hypothalamus and terminating in the neurohypophysis. Oxytocin, a hormone, is carried by these fibers from the hypothalamus, where it is produced, into the neurohypophysis, where it is released.

tract, parietal corticopontine tract arising from cells in the parietal cortex and terminating in the pontine gray. In the monkey it is a large tract but in man its presence has been questioned.

tract, parietopontine see tract, parietal corticopontine.

tract, posterior spinocerebellar see tract, dorsal spinocerebellar.

tract of Probst fiber bundle continuous with the mesencephalic tract of V, at levels caudal to the motor and chief sensory nuclei of V. see also bundle of Probst.

tract, propriospinal see fasciculus proprius.

tract, pyramidal tract whose cell bodies are located in the cerebral cortex and whose axons terminate directly or indirectly in motor nuclei of the brain stem and spinal cord.

tract, quintothalamic see tract, ventral or dorsal secondary ascending, of V.

tracti rubrospinal tract beginning in the red nucleus of the midbrain and terminating in the spinal cord, in man at cervical levels. Syn: Monakow's tract.

tract of Schultze see fasciculus interfascicularis.

tract of Schütz see funiculus, dorsal longitudinal.

tract, secondary ascending visceral multisynaptic ascending neuron chain located in the lateral funiculus of the spinal cord just lateral to the ventral horn, arising from the secondary visceral gray of both sides and carrying impulses from the viscera, including visceral pain, to higher centers.

tract, solitariospinal, of Cajal fibers in the medial reticulospinal tract which carry impulses from nucleus parasolitarius directly or after synapse in reticular gray.

tract, spinal, of V tract composed of descending tactile, pain, and temperature fibers mostly from the face by way of the trigeminal nerve. It is located in the dorsolateral part of the caudal pons and the medulla, overlapping the dorsolateral fasciculus of the spinal cord. Its fibers terminate in the nucleus of the spinal tract of V in the pons, medulla, and upper three or four cervical cord segments. Syn: descending tract of V.

tract, spinoolivary tract composed of fibers arising apparently from cells of the dorsal funicular gray, in man at cervical spinal cord levels. The fibers cross the midline through the ventral white commissure and ascend to the inferior olive along the ventrolateral border of the spinal cord. They are thought to carry proprioceptive and tactile impulses. Syn: Bechterew's bundle.

tract, spinospinal see fasciculus proprius.

tract, spinotectal tract carrying impulses, set off by various kinds of stimuli, from the spinal cord to the superior colliculus.

tract, spinovestibular tract composed of fibers which arise from cells of the dorsal funicular gray in the dorsal horn of upper cervical, and perhaps other spinal cord segments, cross the midline in the ventral white commissure, ascend in the ventral funiculus of the spinal cord, and end in the inferior vestibular nucleus. It carries proprioceptive impulses from nerve endings in the neck and is a link for certain neck reflexes and eye movements.

tract, supraopticohypophysial tract composed of fibers arising in the supraoptic nucleus of the hypothalamus and terminating in the neurohypophysis. It carries vasopressin an aritidiuretic hormone, from the hypothalamus, where it is produced, into the neurohypophysis, where it is released.

tract, tectobulbar tract which arises with and accompanies the fibers of the medial tectospinal tract but which supplies motor nuclei in the brain stem.

tract, tectocerebellar tract arising largely from the nucleus of the inferior colliculus which passes through the anterior medullary velum and ends in the vermis. Probably carries auditory impulses to the cerebellum.

tract, tectopontine tract from the superior colliculus to the base of the pons, probably carrying visual impulses for relay to the cerebellum.

tract, temporal corticopontine tract arising mainly from cells in the superior, middle, and inferior temporal gyri and terminating in the lateral pontine gray.

tract, temporopontine see tract, temporal corticopontine.

tract, thalamobulbar misnomer for the central tegmental tract.

tract, thalamoolivary old term for the central tegmental tract, which does not arise from the thalamus.

tract, trigeminospinal see tract, spinal, of V.

tract of Türck see tract, temporal corticopontine.

tract of Türck, anterior see tract, ventral corticospinal.

tract, uncrossed pyramidal see tract, ventral corticospinal.

tract, uveal see uvea.

tract, ventral central trigeminal see tract, ventral secondary ascending, of V.

tract, ventral corticospinal pyramidal tract fibers which do not cross in the motor decussation but descend into the ventral funiculus of the spinal cord and terminate in the ventral horn at cervical and thoracic cord levels, most fibers crossing in the ventral white commissure. Syn: anterior or direct corticospinal tract; anterior tract of Türck; uncrossed pyramidal tract.

tract, ventral pyramidal see tract, ventral corticospinal.

tract, ventral secondary ascending, of V tract arising from cells in the chief sensory nucleus of V and spinal nucleus of V. Its fibers cross the midline and end in nucleus ventralis posteromedialis of the dorsal thalamus. The tract carries impulses for pain and temperature from the face from the spinal nucleus of V in the closed medulla and spinal cord [C₁‑C₄] and nondiscriminatory [general tactile sensibility from the chief sensory and spinal nuclei of V. Syn: ventral or central trigeminal or quintothalamic tract; ventral trigeminal lemniscus.

tract, ventral spinocerebellar tract which arises bilaterally from dorsal funicular cells [nucleus proprius] in the spinal cord. It loops over the superior cerebella peduncle and ends bilaterally in the cerebellum. Presumably the fibers which cross in the cord cross again in the cerebellum. The tract carries impulses from neurotendinous and tactile endings of the body and terminates as mossy fibers in the vermis [central and culmen] and adjoining part of the hemisphere of the anterior lobe, in the posterior lobe vermis [pyramis and uvula] and in nucleus fastigii. Syn: anterior or indirect spinocerebellar tract; fasciculus or tract of Gowers: superficial anterolateral fasciculus.

tract, ventral spinothalamic crossed tract composed of secondary neurons arising from dorsal funicular cells of the spinal cord and carrying general tactile sensibility from one side of the body to the ventral nucleus of the contralateral dorsal thalamus. Syn: tract of Dejerine.

tract, ventrolateral vestibulospinal tract whose fibers arise from large cells in the lateral vestibular nucleus, descend without decussation into the spinal cord in a position ventral to the ventral horn, and end on ventral horn cells throughout the cord, especially those that supply the lower extremity. The tract is concerned mainly with postural adjustments. Syn: Deiterospinal tract; lateral vestibulospinal tract.

tract, vestibulospinal see tract, ventrolateral vestibulospinal.

tract of Vicq d’Azyr mammillothalamic tract.

tractotomy cutting of a central nervous system tract, especially for the relief of pain.

transcallosal across or through the corpus callosum.

transmitter, neurohumoral see neurotransmitter.

transmitter substance see neurotransmitter.

trapezoid body see body, trapezoid.

triangle see also trigone.

triangle of Gombault and Philippe sacral portion of the septomarginal fasciculus, at the dorsomedial angle of the posterior funiculus.

triangle of the lateral ventricle see atrium of the lateral ventricle.

triangle, Sylvian space indicated in cerebral angiography by the position of branches of the middle cerebral artery on the surface of the insula within the lateral fissure. The anterior superior aspect of the triangle is marked by the first identifiable opercular branch; the anterior inferior aspect is indicated by the most anterior portion of the trunk of the middle cerebral artery or the inferior part of the first opercular branch. The triangle extends posteriorly to the Sylvian point at the posterior limit of the lateral fissure where the last branches of the middle cerebral artery emerge from the lateral fissure. [Taveras and Wood, 1964].

trigone, collateral see atrium of the lateral ventricle.

trigone, hypoglossal elevation on the floor of the fourth ventricle, medial to the vagal trigone, and overlying‑the nucleus of the hypoglossal nerve. Syn: hypoglossal triangle; trigonum hypoglossi.

trigone of the lateral ventricle see atrium of the lateral ventricle

trigone, olfactory triangular area between the diverging medial and lateral olfactory striae.

trigone, vagal elevation on the floor of the fourth ventricle, lateral to the hypoglossal trigone and overlying the dorsal efferent nucleus of the vagus nerve. Syn: ala cinerea; Arnold’s area; trigonum vagi; vagal triangle.

trigonum hypoglossi see trigone, hypoglossal.

trigonum vagi see trigone, vagal.

Trolard, Paulin [1842‑1910] French anatomist. see lakes and vein of Trolard.

truncus corporis callosi [N.A.] see body of the corpus callosum.

tube, neural embryonic tube derived from the neural plate and from which the central nervous system develops.

tuber [L. knot or swelling] subdivision of the cerebellar vermis between the folium vermis and the pyramis.

tuber cinereum elevation on the ventral surface of the diencephalon, between the mammillary bodies posteriorly and the optic chiasm anteriorly.

tubercle, acoustic small swelling on the dorsolateral surface of the medulla, at the attachment of the cochlear nerve, and overlying the cochlear nuclei.

tubercle, anterior elevation on the dorsal, anterior wall of the third ventricle, overlying the anterior nucleus of the dorsal thalamus.

tubercle, cuneate elevation on the dorsolateral surface of the medulla overlying nucleus cuneatus. Syn: tuberculum cuneatum.

tubercle, gracile see clava.

tubercle, olfactory eminence in animals which have a large olfactory system, in the region designated anterior perforated substance in man. Syn: tuberculum olfactorium.

tubercles, quadrigeminal colliculi.

tuberculum acusticum see tubercle, acoustic.

tuberculum cinereum elevation on the lateral surface of the medulla overlying the spinal nucleus of V. Syn: eminentia trigemini.

tuberculum cuneatum see tubercle, cuneate.

tuberculum olfactorium see tubercle, olfactory.

tunnel of Corti axial canal which extends the full length of the cochlear duct between the inner and outer pillars of the organ of Corti.

tunnel, inner see tunnel of Corti.

tunnel, internal spiral see sulcus, internal spiral.

Türck, Ludwig [1810‑1868] Austrian neurologist and laryngologist who described the temporal corticopontine tract [tract of Türck] and the ventral corticospinal tract [anterior tract of Türck].

Turner, William Aldren [b. 1864] British neurologist. see sulcus, intraparietal.

‘tweenbrain see diencephalon.

tympanum ear drum; membrane separating the external auditory meatus and the middle ear.

u

U-fibers see fibers, arcuate.

umbo tip of the handle of the malleus. The handle is attached to the medial surface of the tympanic membrane with the umbo located at the center of the membrane.

uncinate fasciculus [L. uncinatus—hook‑shaped] see fasciculus, uncinate.

uncus [L. hook] protuberance on the medial side of the anterior portion of the parahippocampal gyrus, overlying the amygdala. Syn: uncinate gyrus.

unit, motor motor neuron and the muscle fibers which it supplies.

utricle [L. little womb] subdivision of the membranous labyrinth, an ovoid, slightly flattened sac in the superoposterior region of the vestibule of the bony labyrinth and connected with the semicircular ducts and, by the utriculosaccular duct, with the saccule.

uvea [L. uva—grape] vascular tunic of the eye, consisting of the choroid, ciliary body, and iris. Syn: uveal tract.

uvula subdivision of the cerebellar vermis, separated from the nodule by the . postnodular fissure and from the pyramis by the prepyramidal fissure.

v

vagus [L. wandering] the vagus nerve; cranial nerve X.

vallecula cerebellar /va“l-e“k'u“-la/ [L. vallecula—little valley] [B.N.A] deep median fossa between the two cerebellar hemispheres on the inferior surface of the cerebellum.

valve of Vieussens see velum, anterior medullary.

Varolius, Constanzio [1543‑1575] Italian anatomist known mainly for his studies of the brain. He described the pons [pons Varolii] in 1573. He also gave the hippocampus its name.

vas prominens large capillary loops within the spiral prominence.

vas spirale small artery which runs the length of the cochlea between the basilar membrane and the mesothelium of the scala tympani.

vasa corona plexus of small arterial vessels on the lateral and ventral surfaces of the spinal cord whose penetrating branches supply a narrow zone of the underlying white matter.

vasa nervorum small blood vessels within peripheral nerve trunks.

vasopressin mainly an antidiuretic neurohypophysial hormone, but it also has a minor role in vasoconstriction. It is produced by cells of the supraoptic nucleus, transported by axoplasmic flow along fibers of the supraopticohypophysial tract to the neurohypophysis, where it is released.

Vater, Abraham [1684‑1751] German anatomist who first noted the large encapsulated nerve endings [Pacinian corpuscles] later rediscovered and described by Pacini.

vegetative nervous system see system, autonomic nervous.

vein, anterior cerebral vein which drains the orbital surface of the frontal lobe and the anterior portions of the corpus callosum and cingulate gyrus, then joins the deep cerebral vein to form the basal vein.

vein, basal vein formed by the union of the anterior vein of the corpus callosum, the deep middle cerebral, and the anterior cerebral veins. It courses posteriorly around the brain stem, joins the internal cerebral vein, and empties into the great cerebral vein. Syn: basal cerebral vein; basilar vein, vein of Rosenthal.

vein, basilar see vein, basal.

vein[s] of Breschet see veins, diploic.

vein of Brown vein of the septum pellucidum.

vein, Charpy’s anastomotic see vein, posterior communicating.

vein, deep middle cerebral vein deep within the lateral fissure, It drains blood from the insula, and from the lenticulostriate veins, then joins the anterior cerebral vein to form the basal vein.

vein[s], diploic plexus of veins between the inner and outer tables of the calvarium, and which communicates with the intracranial and extracranial venous systems. Syn: veins of Breschet.

vein, emissary any vein which by connections through the skull connects a dural sinus and the extracranial venous system.

vein of Galen see vein, great cerebral.

vein, great cerebral short, midline vein formed by the fusion of the two internal cerebral veins, just above the pineal body. It empties into the straight sinus. Syn: [great] vein of Galen; vena magna.

vein, greater anastomotic anastomotic vein on the surface of the cerebrum, connecting the superficial middle cerebral vein and the superior longitudinal sinus. Syn: superior anastomotic ‑vein; vein of Trolard.

vein, great, of Galen see vein, great cerebral.

vein, inferior anastomotic see vein, lesser anastomotic.

veins, inferior cerebral superficial veins which drain the lower part of the lateral surface of the occipital and temporal lobes and which empty into the transverse sinus.

vein of Labbé see vein, lesser anastomotic.

vein, lesser anastomotic anastomotic vein on the surface of the cerebrum, connecting the superficial middle cerebral vein and the transverse sinus. Syn: posterior or inferior anastomotic vein; vein of Labbé.

vein, lesser, of Galen internal cerebral vein.

vein, middle cerebral one of two veins [superficial and deep] located along the lateral fissure of the cerebrum. Syn: Sylvian vein.

vein, posterior anastomotic see vein, lesser anastomotic.

vein, posterior communicating vein, sometimes fairly large, sometimes indistinguishable, which accompanies the middle collicular artery and empties into the basal vein Syn: Charpy's anastomotic vein.

vein, Rolandic vein which lies along the central sulcus on the lateral surface of the cerebrum, and which empties into the superior longitudinal sinus, but also usually communicates with one of the middle cerebral veins.

vein of Rosenthal see vein, basal.

vein, septal vein in the septum pellucidum on the medial side of the anterior horn of the lateral ventricle. It empties into the internal cerebral vein at the venous angle.

vein, small, of Galen internal cerebral vein.

vein, striothalamic see vein, terminal.

vein, superficial middle cerebral superficial vein which runs forward along the lateral fissure, turns medially along the sphenoid ridge, and ends in the cavernous sinus or in the sphenoparietal sinus.

vein, superior anastomotic see vein, greater anastomotic.

vein[s], superior cerebral superficial veins which run upward on the surface of the cerebrum to empty into the superior longitudinal sinus.

vein, Sylvian see vein, middle cerebral.

vein, terminal vein which accompanies the tail of the caudate nucleus along the roof of the inferior horn of the lateral ventricle, then turns forward and runs along the junction of the body of the caudate nucleus and the dorsal thalamus on the floor of the body of the lateral ventricle to the interventricular foramen, where it joins the internal cerebral vein at the venous angle. Syn: striothalamic vein; thalamostriate vein.

vein, thalamostriate see vein, terminal.

vein[s], transcerebral connecting vessels between the cortical veins and internal cerebral system of veins.

vein of Trolard see vein, greater anastomotic.

veins, vertebral system of valveless epidural and perivertebral veins of the vertebral column and their connections with other valveless veins including those of the brain and spinal cord on the one hand and those of the thorax, abdomen, and pelvis on the other. Among other things this plexus plays an important role in metastasis from the body to the brain [Batson, 1957].

velum, anterior medullary /ve“'lum/ [L. velum—veil or covering] thin layer of tissue between the two superior cerebellar peduncles and forming a roof over the rostral part of the fourth ventricle. Syn: superior medullary velum; valve of Vieussens.

velum, inferior medullary see velum, posterior medullary.

velum interpositum pia mater and connective tissue occupying the space between the corpus callosum dorsally and the thalamus, choroid plexus of the third ventricle and pineal body ventrally, and through which the internal cerebral veins pass.

velum, posterior medullary membranous roof over the caudal part of the fourth ventricle. Syn: inferior medullary velum; tela choroidea of the fourth ventricle.

velum, superior medullary see velum, anterior medullary.

velum terminale see lamina terminalis.

vena magna see vein, great cerebral.

vena terminalis see vein, terminal.

ventricle irregularly shaped cavity within the central nervous system, which contains cerebrospinal fluid.

ventricle of Arantius area of transition from the caudal portion of the fourth ventricle to the central canal.

ventricle, fifth see cavum septi pellucidi.

ventricle, first either one of the two lateral ventricles.

ventricle, fourth cavity within the hindbrain. It is bounded ventrally by the pons and open medulla and dorsally by the anterior medullary velum, cerebellum, and posterior medullary velum. It communicates rostrally with the cerebral aqueduct and caudally with the central canal.

ventricle of Krause see ventricle, terminal.

ventricle, lateral irregularly shaped cavity within each cerebral hemisphere. It consists of an anterior horn in the frontal lobe, a body mostly in the parietal lobe, a posterior horn in the occipital lobe, an inferior horn in the temporal lobe, and an atrium at the junction of the body and posterior and inferior horns. It communicates with the ventricle through the interventricular foramen.

ventricle, second either one of the two lateral ventricles.

ventricle, terminal moderately dilated portion of the central canal in the caudal segments of the spinal cord. Syn: ventricle of Krause.

ventricle, third midline cavity between the two halves of the diencephalon and extending rostrally into the telencephalon medium. It communicates with each lateral ventricle through an interventricular foramen and caudally is continuous with the cerebral aqueduct.

Verga, A. [1811‑1895] Italian anatomist and psychiatrist. The ventricle of Verga is the posterior extension of the cavity of the septum pellucidum.

vermis [L. worm] median portion of the cerebellum between the two cerebellar hemispheres. see cerebellum, lobules for the subdivisions of the vermis.

vertigo [L. vertere—to turn] sensation of turning, as if the external world were moving or revolving around the patient, or as if he himself were moving or revolving in space.

vesicle, otic closed sac derived from the superficial ectoderm, from which the membranous labyrinth develops. Syn: otocyst.

vestibule 1. central cavity of the bony [perilymphatic] labyrinth, continuous with the cochlea anteriorly, and with the semicircular canals which lie above and lateral to it, and which contains the utricle and saccule. 2. see atrium of the lateral ventricle.

vestibulocerebellum portion of the cerebellum dominated by impulses relayed by vestibular connections, particularly the flocculonodular lobe. Syn: archicerebellum.

Vicq d’Azyr, Félix [1748‑1794] French anatomist who described the mammillothalamic tract [tract of Vicq d’Azyr] in 1781. The stripe of Vicq d’Azyr is a layer of nerve fibers in layer II of the cerebral cortex.

Vidanius, G. [1500‑1567] anatomist and physician of Paris, later of Pisa.

Vieussens, Raymond [1641‑1716] French anatomist. In 1685 he described the ansa hypoglossi, anterior medullary velum [valve of Vieussens], celiac plexus, pyramids, olives, and the centrum ovale. In 1706 he described the ansa subclavia [anulus of Vieussens].

villi, arachnoid small projections which invaginate the dura mater and project into the dural venous sinuses, usually the superior sagittal sinus, and through which cerebrospinal fluid enters the venous system.

vinculum [L. band or ligament] bridge of gray matter connecting the nucleus of the spinal tract of V and the central gray of the medulla.

Virchow, Rudolf Ludwig Karl [1821‑1902] German pathologist, a student of Müller’s. He is known as the founder of cellular pathology. In 1851 he noted the spaces around blood vessels in sections of brain. These spaces [spaces of Virchow‑Robin] were later described in greater detail by Robin.

visual purple see rhodopsin.

vomeronasal for vomeronasal nerve; organ, see the nouns.

Waldeyer layer or cells layer of marginal cells on the surface of the dorsal horn of the spinal cord. see also gray, dorsal funicular.

Wallenberg, Adolf [b. 1862] German physician who described the lateral medullary syndrome [Wallenberg’s syndrome, posterior inferior cerebellar artery syndrome]. see fibers of Wallenberg‑Klimoff.

Waller, Augustus Volney [1816‑1870] English physiologist who demonstrated that the nerve fiber is dependent on its cell body for nutrition and functional integrity, and showed that nerve fibers separated from their cell bodies undergo complete degeneration [Wallerian degeneration].

Weigert, Karl [1843‑1905] German pathologist who introduced a number of staining procedures, particularly one for myelin sheaths in 1882 [Weigert stain].

Wernekinck, Friedrich Christian Gregor [1798‑1835] German anatomist who described the decussation of the superior cerebellar peduncles [decussation or commissure of Wernekinck],

Wernicke, Carl [1848‑1905] German psychiatrist who described several neurologic disorders including sensory aphasia [Wernicke’s aphasia].

Westphal, Carl Friedrich Otto [1833‑1890] German neurologist. see nucleus, Edinger‑Westphal.

Wilder, interventricular antrum of see antrum, interventricular, of Wilder.

Willis, Thomas [1621‑1675] English physician, noted for his contributions to the anatomy of the brain. In 1664 he reclassified the cranial nerves and described the anastomosing arteries on the base of the brain [circle of Willis] and the spinal accessory nerve [accessory nerve of Willis].

Winer, Jeffery A. [1959- ] neuroanatomist who destroyed the circadian clocks of an entire generation of Berkeley students with classes at 8:00 a.m. and office hours at 3:00-5:00 p.m. on Tuesday, Thursday, and Friday. Famous for not winning a Nobel prize.

window, cochlear opening between the scala tympani of the cochlea and the tympanic cavity, which is closed by the secondary tympanic membrane. Syn: fenestra cochleae; round window.

window, oval see window, vestibular.

window, round see window, cochlear.

window, vestibular opening between the tympanic cavity and the scala vestibuli of the cochlea, into which the footplate of the stapes fits. Syn: oval window; fenestra ovale; fenestra vestibuli.

Wrisberg, Heinrich Auguste [1739‑1808] German anatomist, who described the medial cutaneous nerve of the arm and the intermediate nerve [both called nerve of Wrisberg].

z

Zinn, Johann Gottfried [1727‑1759] German anatomist and physician who published a classical treatise on the eye in 1755.

zona arcuata portion of the basilar membrane of the cochlea, between the tympanic lip of the limbus laminae spiralis and the outer pillars.

zona incerta nucleus of the ventral thalamus, important as a way station from the striatum in the extrapyramidal system. It is located dorsal to the subthalamic nucleus, from which it is separated by the lenticular fasciculus. The thalamic fasciculus separates it from the dorsal thalamus.

zona pectinata portion of the basilar membrane of the cochlea, between the outer pillars and the crest of the spiral ligament.

zona terminalis [N.A.] see fasciculus, dorsolateral.

zone of Lissauer see fasciculus, dorsolateral.

Zuckerkandl, Emil [1849‑1910] Austrian anatomist. For Zuckerkandl's bodies see body, chromaffin; for Zuckerkandl's convolution, see gyrus, subcallosal; for Zuckerkandl's olfactory radiations, see band, diagonal, of Broca.

References

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Crosby, E. C.; T. Humphrey; and E. Lauer [1962]. Correlative Anatomy of the Nervous System. Macmillan and Co., New York.

Herrick, C. J. [1918]. An Introduction to Neurology. W. B. Saunders, Philadelphia.

List, C. F. [1969. Developmental anomalies of the craniovertebral border. In Correlative Neurosurgery, 2nd edition [E. A. Kahn, E. C. Crosby, R. C. Schneider, and J. A. Taren, eds.]. Charles C Thomas Co., Springfield, Illinois, pp. 432‑443.

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Ramón y Cajal, S. [1911]. Histologie du système nerveux de l’homme et des vertébrés. Maloine, Paris. [Reprinted 1955 by Instituto Ramón y Cajal, Madrid.]

Rexed, B. [1964]. Some aspects of the cytoarchitectonics and synaptology of the spinal cord. In Prog. Brain Res. Vol. 11. Organization of the Spinal Cord [J. C. Eccles, J. P. Schadé, eds.], pp. 58‑92.

Taveras, J. M., and E. H. Wood [1964]. Diagnostic Neuroradiology. Williams and Wilkins Co., Baltimore.