Vagal tone refers to the
A. decreasing of the heart rate below its inherent rhythm by parasympathetic stimulation.
B. decreasing of the heart rate below its inherent rhythm by sympathetic stimulation.
C. increasing of the heart rate above its inherent rhythm by sympathetic stimulation.
D. increasing of the heart rate above its inherent rhythm by parasympathetic stimulation.
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Question 2) The hearts nodal cells have a more negative resting potential than neurons do, because nodal cells lack leak channels for sodium and potassium ions.
Indicate whether this statement is true or false.
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Question 3) An autorhythmic heart cell is one in which
A. action potentials fire spontaneoulsy.
B. action potentials are stimulated by internal stores of acetylcholine.
C. action potentials always occur at exactly the same frequency.
D. all filaments contract and relax with a high degree of synchrony.
E. action potentials are initiated by the autonomic nervous system.
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Question 4) . SA nodal cells are autorhythmic.
Indicate whether this statement is true or false.
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Question 5) For the repolarization phase of an SA nodal cell action potential,
A. sodium and potassium channels open.
B. calcium channels open and sodium channels close.
C. calcium and potassium channels close.
D. calcium channels close and potassium channels open.
E. sodium and chloride channels open.
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Question 6) Once an SA nodal cell reaches threshold, the depolarization phase occurs during which
A. potassium comes in through fast voltage-gated channels.
B. calcium comes in through fast voltage-gated channels.
C. potassium moves out through fast voltage-gated channels.
D. sodium moves out through slow voltage-gated channels.
E. calcium moves out through slow voltage-gated channels.
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Question 7) Which valve prevents the backflow of blood into the left ventricle when the ventricles relax?
A. Left atrioventricular valve
B. Aortic semilunar valve
C. Right atrioventricular valve
D. Pulmonary semilunar valve
E. None of the choices is correct.
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Question 8) How many half-moon shaped, pocketlike cusps are found in each semilunar valve?
A. 1
B. 2
C. 3
D. 4
E. 6
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Question 9) Which action leads to the closure of the right atrioventricular valve?
A. Contraction of the right atrium
B. Contraction of the left atrium
C. Contraction of the right ventricle
D. Relaxation of the right ventricle
E. Relaxation of the left atrium
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Question 10) Metabolically, cardiac muscle relies on
A. aerobic metabolism using glycolysis of glycogen to meet most ATP demands.
B. aerobic metabolism using many mitochondria and a rich supply of myoglobin.
C. anaerobic metabolism using glycolytic enzymes to quickly generate ATP.
D. anaerobic metabolism using myoglobin, creatin kinase, and ketone bodies.
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