When comparing cardiac muscle cells and skeletal muscle cells,
A. the rate of action potential propagation is faster in cardiac muscle.
B. both possess intercalated discs.
C. only skeletal muscle has a plateau phase in its contraction cycle.
D. action potentials are conducted from cell to cell only in cardiac muscle.
E. both are voluntary.
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Question 2) The long refractory period observed in cardiac muscle
A. prolongs depolarization of the cardiac muscle.
B. prevents tetanic contractions of the cardiac muscle.
C. ensures that the heart has adequate time to contract.
D. prevents the heart rate from slowing down.
E. prevents an increase in heart rate.
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Question 3) What action is most responsible for the resting membrane potential in cardiac muscle cells?
A. movement of K+ through voltage-gated K+ channels
B. movement of Na+ through open Na+ channels
C. movement of Ca2+ through voltage-gated Ca2+ channels.
D. closing of Na+ and K+ voltage-gated channels
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Question 4) Which of the following areas of the conduction system would produce spontaneous action potentials most frequently if the SA node were not functioning?
A. AV bundle
B. Purkinje fibers
C. AV node
D. bundle branch
E. the pacemaker
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Question 5) Which of the following would result from a reduced function of the sodium channels in the SA node?
A. depolarization would be delayed
B. the heart rate would decrease
C. repolarization would not occur
D. a shortened plateau phase
E. depolarization would be delayed and the heart rate would decrease
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Question 6) Which of the following is mismatched?
A. opening of sodium channels - depolarization
B. closing of calcium channels - plateau phase
C. opening of potassium channels - rapid repolarization
D. closure of sodium channels - early repolarization
E. opening of calcium channels - plateau phase
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Question 7) If the SA node is nonfunctional, which of the following is most likely to occur?
A. The heart will go into asystole (stop).
B. Tachycardia will develop.
C. Another portion of the heart will become the pacemaker.
D. The heart will go into defibrillation.
E. The heart will be desensitized.
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Question 8) When a pacemaker potential in the SA node reaches threshold,
A. the permeability to K+ ions increases.
B. many voltage-gated Ca2+ channels open.
C. voltage-gated Ca2+ channels close.
D. RMP has been restored.
E. permeability of the cell does not change.
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Question 9) Depolarization of a cardiac muscle cell occurs as the result of
A. a decrease in the permeability of the cell membrane to sodium.
B. the opening of voltage-gated sodium channels and voltage-gated calcium channels.
C. the closure of voltage-gated calcium channels.
D. the opening of voltage-gated potassium channels.
E. the closure of the voltage-gated sodium channels.
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Question 10) Calcium channel blockers are frequently used to
A. increase the heart rate.
B. treat tachycardia or other arrhythmias.
C. speed up conduction of impulses through the AV node.
D. slow the closing of potassium ion channels.
E. treat bradycardia and low blood pressure.
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