MCB 136 - Advanced Physiology
Course Info Tissue, Cells and Membranes Endocrine and Autonomic Muscle and Cardiovascular Respiration Gastrointestinal Kidney and Body Fluids

MCB 136 Review | Muscle & Cardiovascular

Review Questions   |   Skeletal, Cardiac and Smooth Muscle

Be able to distinguish anatomical and molecular structures of skeletal muscles and cardiac muscles, including sarcomeres, intercalated discs, gap junctions, Z-lines, actin, myosin, troponin, tropomyosin, nebulin and titin, RyR, transverse tubules, Ca-ATPase (PMCA and SERCA), phospholamban, Na/Ca exchanger.

Be able to describe the interactions between Ca and Tn that give rise to control of skeletal and cardiac muscle contraction. Compare this to control of smooth muscle contraction by Ca and myosin light chain kinase. How do all the muscles relax?

Distinguish among the following types of skeletal muscles: fast twitch, glycolytic; fast twitch oxidative; slow twitch oxidative. Mention size, aerobic vs anaerobic mechanisms for generating ATP, presence of myoglobin and mitochondria.

  1. T or F? Skeletal muscle cells have more than one nucleus.


  2. The modified endoplasmic reticulum in skeletal and cardiac muscle is called the ___, and it actively accumulates ___ during the relaxation phase.


  3. Ca permeability of the plasma membrane of the three different types of muscle cells is in the order __ and __ >> ___.


  4. T-tubules allow __ to move to the interior regions of skeletal and cardiac muscle.


  5. If a heart cell had a genetic defect in its titin molecules such that its normal function was altered, how might this affect heart function?


  6. Which of the following is an ATPase?   G-actin, F actin, myosin, myosin light chain, titin, troponin


  7. Inositol trisphosphate receptors are found in __ muscle cells, while ryanodine receptors are found in __ muscle cells.


  8. Explain the differences between twitch, summation, and tetanus, and also why skeletal muscle exhibits tetanic contractions but cardiac muscle does not.


  9. Describe the interactions between actin and myosin during contraction and relaxation, i.e., the sliding filament model.


  10. Which type of muscle is the most efficient in terms of generating force for a given amount of ATP? Which type of muscle contracts the most slowly?


  11. What determines different forces involved in picking up a pencil vs picking up a 10 pound weight?


  12. Curare is a poison that paralyzes muscles without affecting release of acetylcholine. The muscles can still contract if an electrical stimulus is applied directly to the muscle. What does curare do?


  13. A muscle was experimentally put into a rigor state by removal of ATP (with a method that allows access to the insides of the cells). What would happen to the muscle if ATP were added in the presence vs the absence of Ca?


  14. T or F?   Fatigue of cardiac muscle is caused when [ATP] decreases to zero.


Review Questions   |   Coordinated activities of heart and blood vessels

Define: P-V loop, systole and diastole; ventricular filling; atrial contraction; isovolumetric ventricular contraction; ventricular ejection (how much is ejected?); isovolumetric ventricular relaxation. Be able to locate these aspects of cardiac function on a "pressure-volume loop." Also, calculate stroke volume and "ejection fraction" from the diagram.

Describe the structure of the heart, including chambers, valves, major vessels entering and leaving, as well as endo-, epi- and myocardium, valves, papillary muscles, chordae tendinae, SA and AV nodes, Purkinje fibers, coronary blood supply. How is valve structure related to valve function? Indicate the sequential participation of specific heart valves during the above pumping cycle.

  1. What would happen to cardiac muscle contractility and excitability in the presence of drugs that specifically block Ca channels in the plasma membrane?


  2. Name the different functions of ATP during normal contractile cycle of the heart.


  3. Caffeine causes the RyR to release Ca and also has effects on cAMP metabolism (see signaling). What might caffeine do to the heart's contraction?


  4. Offer explanations for why epinephrine increases: contraction strength and rate of relaxation.


  5. Why can't the heart contract tetanically?


  6. Which of the following causes Na channels in heart muscle to open?
        a. Hyperpolarization
        b. depolarization
        c. increases in cell Ca
        d. activation of the acetylcholine receptor


  7. What provides nutrition to the heart muscle cells?
        a. blood in the atria and ventricles
        b. pulmonary artery
        c. pulmonary vein
        d. coronary blood vessels
        e. none of the above.

    Why is does a heart attack occur when this blood supply is blocked? What blood components are analyzed to determine whether a patient has had a heart attack?

  8. T or F?   Cardiac action potentials proceed in the sequence: atria, SA node, bundle of His, AV node, ventricles


  9. Why is it so disastrous to the heart to elevate extracellular [K] very rapidly? Explain in terms of voltage-dependent Na channels, K channels, membrane voltage, activation and inactivation.


  10. What is difference between single-unit and multi-unit smooth muscle?


  11. How are smooth muscle and cardiac muscle different in terms of their requirement for electrical excitation before contraction?


  12. How do the neurotransmitters norepinephrine and acetylcholine affect cardiac vs smooth muscle?


  13. T or F?   Cutting the vagus nerve causes the heart to speed up. Explain your answer.


  14. T or F?   End diastolic volume is equal to about 150 ml, and end systolic volume is about 0 ml, so the stroke volume equals 150 ml.


  15. T or F?   Stroke volume of the left ventricle is larger than that of the right ventricle.

Review Questions   |   Hemodynamics and Vessel Functions

Define: Diffusion and bulk flow; Poiseuille's law (also how flow in CV system is related to pressure difference and resistance); systemic and pulmonary circulations; cardiac output and relationship to stroke volume and heart beat rate; aorta, arteries, arterioles, capillaries, veins; main structural and functional differences between arteries, arterioles, capillaries and veins; change in velocity, pressure and area as traverse CV system; Law of Laplace; resistance to blood flow, peripheral resistance; compliance; venous valves

Review the relative internal diameters, wall thickness, and amounts of the principal components of the various blood vessels and indicate functional implications of such composition.

    1. During exercise cardiac output often increases by 2 - 4 fold, but mean arterial pressure often exhibits no increase. In terms of cardiac output and peripheral resistance, explain this effect.
    2. If resistance of vessels supplying the gastrointestinal tract increases, explain what would happen (assuming no other changes in the system) to blood flow in vessels of the GI tract and to mean arterial pressure.


  2. Matching.
    a. arterioles
    b. arteries
    c. capillaries
    d. veins
    e. aorta     		i. store pressure generated by the heart
    ii. have walls that are stiff and elastic
    iii. carry low oxygen blood
    iv. have endothelial lining
    v. act as a volume reservoir
    vi. blood flows slowest here
    vii. have lowest blood pressure
    viii. sites of variable resistance
    ix. have large compliance
    x. blood flows fastest here


  3. Aortic pressure reaches a high of ~__ mm Hg, also called the ___ pressure, and a low of ~__ mm Hg, also called the ___ pressure.


  4. If an arteriole contracted such that its diameter was reduced by a factor of 2, what would be magnitude of change in blood flow through the vessel? Assume pressure remained constant.


  5. The net flux of a solute that moves by passive diffusional mechanism is:
        a. a linear function of area available for diffusion.
        b. a linear function of the concentration difference for the solute across the barrier.
        c. directly proportional to the distance of diffusion.

  6. For a skeletal muscle cell, [Ca] must rise in all parts of the cell within 200 msec. What is the maximum radius that would allow diffusion of Ca from the plasma membrane to the center of the cell to accommodate this requirement? Assume diffusion coefficient for Ca is 10–5cm2/sec. Use the Einstein equation: (Dx)2 = 2Dt.


  7. Calculate the pressure declines and resistances of the arteries, arterioles, capillaries and veins.


  8. Be able to locate the following in the CV system: aorta, arterioles, capillary beds, venules, veins, right atrium, right ventricle, left atrium, left ventricle. What are the two major circuits (circulations) of the CV system? Name three general differences between the two major circuits.


  9. Sketch curves of approximate pressure, velocity of flow, cross-sectional area, and capacity of the blood vessels of the sytemic circulation (from aorta to venae cavae). Is there a pressure gradient between the aorta and arteries? Where is the pressure gradient the greatest in the systemic circulation? Why?


  10. An artery was cannulated and attached to a thin glass tube. If systolic/diastolic pressures were 120 mm Hg/80 mm Hg, how high did the column of blood rise above the person's heart during these two phases of the heart cycle?   1 cm H20 = 0.74 mm Hg.


  11. What is pulse pressure?


  12. What is turbulent vs laminar flow, and how is turbulent blood flow used to measure blood pressure?


  13. What is Law of Laplace, and why is it important for capillaries vs arterioles? How do Law of Laplace and Starling's Law of the Heart tend to counteract each other in the contraction of the heart?


  14. Where is the transmural pressure greatest in a standing person? Left ventricle, aorta at the level of the kidney or artery in the brain? What happens when the person lies down? Explain.


  15. Graph the pressure (x axis) - volume (y axis) relationship for an artery and vein and state the relative compliances of the arterial and venous systems.

Review Questions   |   Capillary exchange: diffusion and osmosis, lymphatics and edema

  1. Explain the roles of filtration and osmosis in determining direction of fluid flow across capillary walls during protein deficiency.


  2. What happens to capillary fluid pressure when precapillary sphincter muscle controlling blood flow into the capillary bed dilates?


  3. Which of the following is/are important in determining flux of oxygen from capillaries to muscles?
        a. oxygen concentration in the muscles
        b. oxygen concentration in the capillaries
        c. carbon dioxide concentration in the muscles
        d. colloid osmotic pressure of plasma
        e. hydrostatic pressure of the capillaries
        f. rate of blood flow through the capillaries
        g. distance from capillary to the muscle cells
        h. diameter of the capillary

  4. Which of the following is not found in capillaries?
        a. smooth muscle
        b. valves
        c. endothelial cells
        d. basal lamina
        e. elastin
        f. tight junctions

  5. What pressure forces are involved in causing lymph flow from the feet to return to the veins?


  6. What type of transport (diffusion or osmosis or filtration) is important for delivery of the following substances across the capillary walls?
        a. glucose
        b. oxygen
        c. carbon dioxide
        d. proteins
        e. amino acids
        f. lactic acid
        g. water

  7. Explain the significance of the following statement: total osmotic pressure of plasma is much larger than the colloid osmotic pressure.

Review Questions   |   Regulation of blood pressure and flow

Define: Frank-Starling mechanism; increased venous return due to muscle pump and respiratory pump; regulation of heart by sympathetic (including epinephrine) and parasympathetic nerves, including effects on rate of contraction and strength of contraction; local control of blood vessels due to myogenic mechanism (nitric oxide?) and metabolic regulation; regulation of arterioles by sympathetic and parasympathetic nerves; roles of blood volume, peripheral resistance and compliance in determination of arterial blood pressure and pulse pressure; baroreceptors (location and afferent nerves); cardiovascular center; "local control" (self-regulation or autoregulation) and metabolic regulation of arteriolar resistance in tissue beds and reflex control during hemorrhage; nerve fibers that innervate the heart, cardiac cells innervated, neurotransmitters released and receptors involved.

  1. What is the advantage of regulation in which increased flow velocity leads to release of nitric oxide from endothelial cells?


  2. What role does the Frank-Starling relationship play in normal physiology of the heart? What is contractility and how is it altered by sympathetic nerves?


  3. What is the equation relating cardiac output and total peripheral resistance to mean arterial pressure? How do stroke volume and arterial compliance contribute to pulse pressure?


  4. Do arterioles receive a supply of sympathetic nerve fibers? What neurotransmitter is released and what receptors are present in arteriolar smooth muscle? Do blood vessels in the brain and coronary circulation respond to sympathetic stimulation? Are arterioles innervated by parasympathetic nerves? What effect is observed when epinephrine binds to the alpha receptor in most vascular beds? What is the effect on skeletal muscle arterioles (why)?


  5. There can be competition between local control dilation and sympathetic vasoconstriction. Which response most often predominates (particularly in brain and heart)?


  6. What and where are baroreceptors? What is the routing of their information such that ultimately the sympathetic and parasympathic nerves are involved? What is the information content of the baroreceptor signals?


  7. During response to hemorrhage, which of the following is increased, decreased or no change?
    1. total peripheral resistance
    2. hematocrit
    3. rate of depolarization of action potential in SA node
    4. blood flow to kidneys
    5. blood flow to GI tract
    6. blood flow to skin
    7. frequency of action potentials in afferent nerves from baroreceptors to medulla
    8. frequency of action potentials in sympathetic nerves to blood vessels in the muscles
    9. heart rate