16
16. Which of the following is not a feature of SA node?
A. SA node has autorhythm. B. SA node determines heart rate. C. SA node has stable resting potential. D. SA node is localized in right atrium. E. SA node is localized near superior vena cava.
17. If the ECG exhibits a regular interval between adjacent normal P waves but the heart beats irregularly,
A. the SA node is not functioning normally. B. the signals from SA node may be blocked at AV node. C. the atria do not contract regularly. D. the AV valves can close only partially. E. the AV valves can open only partially.
18. The average resting cardiac cycle takes about 0.8 sec, including ___.
A. 0.5 sec for ventricular systole and 0.3 sec for ventricular diastole. B. 0.6 sec for ventricular systole and 0.2 sec for ventricular diastole. C. 0.4 sec for ventricular systole and 0.4 sec for ventricular diastole.
D. 0.3 sec for ventricular systole and 0.5 sec for ventricular diastole. E. 0.7 sec for ventricular systole and 0.1 sec for ventricular diastole.
19. Which of the following is the right sequence of phases in a cardiac cycle?
A. atrial contraction, ventricular filling, isovolumic ventricular relaxation, ventricular ejection, isovolumic ventricular contraction
B. ventricular filling, atrial contraction, isovolumic ventricular relaxation, ventricular ejection, isovolumic ventricular contraction
C. ventricular filling, atrial contraction, isovolumic ventricular contraction, , ventricular ejection isovolumic ventricular relaxation
D. atrial contraction, ventricular filling, isovolumic ventricular contraction, ventricular ejection, isovolumic ventricular relaxation
E. isovolumic ventricular relaxation, atrial contraction, ventricular filling, isovolumic ventricular contraction, ventricular ejection
20. A heart rate of 45 beat/min (bpm) and the absence of P waves from the electrocardiogram would suggest ___.
A. ventricular fibrillation. B. ventricular flutter. C. a bundle branch block.
D. aortic stenosis. E. damage to the SA node.
21. The amount of blood (ml) ejected by one ventricle in one heartbeat is called ___.
A. the ejection fraction. B. the preload. C. the afterload. D. the stroke volume.
E. the cardiac output.
22. Atrial systole begins ___.
A. immediately before the P wave. B. immediately after the P wave. C. during the Q wave.
D. during the S-T segment. E. immediately after the T wave.
23. The cardiac center, which modifies the heart rate, is located in ___.
A. the hypothalamus. B. the cerebral cortex C. the carotid sinuses. D. the aortic arch.
E. the medulla oblongata.
24. The cardioinhibitory center communicates with the heart by way of ___.
A. the ventricular muscles. B. parasympathetic nerves. C. the bundle of His.
D. the Purkinje fibers. E. sympathetic nerves.
25. At the end of ventricular contraction, the amount of blood remaining in the ventricle is ___.
A. the end-diastolic volume. B. the end-systolic volume. C. the stroke volume.
D. the residual volume. E. the ejection fraction.
26. The heart’s normal ___ of 54% can rise to as high as 70% during exercise.
A. end-diastolic volume. B. end-systolic volume. C. ejection fraction. D. residual volume.
E. stroke volume.
27. Pressure in the arteries that opposes the opening of the semilunar valves is called ___.
A. ejection pressure. B. venous return. C. afterload. D. preload. E. stroke volume.
28. The second heart sound immediately follows ___.
A. closing of the AV valves. B. the end of diastole. C. the P wave. D. the QRS complex.
E. closing of the aortic and pulmonary valves.
29. The conduction of electrical signals is fastest in ___.
A. the atria. B. the regular ventricular muscle cells. C. the Purkinje fibers.
D. the SA node. E. the AV node.
30. One way of stating the Frank-Starling law of the heart is that stroke volume is proportional to ___.
A. the end-systolic volume. B. the end-diastolic volume. C. the afterload.
D. the heart rate. E. contractility.
31. Baroreceptors are located in ___.
A. the aorta and carotid sinuses. B. the superior and inferior venae cavae. C. the pulmonary arteries.
D. the internal and external jugular veins. E. the ventricles.
32. Given the stroke volume of 80 ml, end-diastolic volume of 160 ml, and a cardiac output of 6.4 L/min, the heart rate is ___.
A. 20 bpm. B. 40 bpm. C. 60 bpm. D. 80 bpm. E. 100 bpm.
33. During isovolumetric contraction, the pressure in the ventricles ___.
A. rises rapidly. B. falls rapidly. C. remains constant. D. rises and then falls.
E. falls and then rises.
34. Hypercapnia (high CO2 in the blood) has the effect of ___.
A. increasing the heart rate. B. decreasing the heart rate. C. decreasing myocardial contractility.
D. increasing refractory period. E. reducing the ejection fraction.
35. The effect of vagal tone on the heart is to ___.
A. decrease ventricular contractility. B. decrease stroke volume. C. decrease heart rate.
D. decrease P-R interval. E. decrease R-R interval.
36. The heart rate is increased by ___.
A. hypothyroidism. B. acetylcholine. C. hyperkalemia. D. hypernatremia.
E. hypercalcemia.
37 An anatomical arrangement that reduces the risk for myocardial infarctions is ___.
arterial anastomoses in the coronary circulation. the desmosomes of the intercalated discs.
continuous blood flow. gap junctions in the myocardium. circumflex arteries.
38. A substance that reduces the heart rate is said to exert ___.
a positive inotropic effect. a negative chronotropic effect. a positive barotropic effect.
a negative inotropic effect. a positive chemotropic effect.
39. Which of the following decreases the heart rate?
Epinephrine acetylcholine norepinephrine thyroid hormone nicotine
40. Because the human heart has autorhythm, ___.
it will beat even if all nerves to it are severed. both ventricles pump the same amount of blood.
it is not subject to the influence of hormones. it is not subject to the influence of nerves.
it is more vulnerable to the lack of blood supply.
41. Which of the following phases occurs right after ventricular ejection?
A. atrial contraction. B. ventricular filling. C. isovolumic ventricular contraction. D. isovolumic ventricular relaxation.
42. Can both tricuspid and pulmonary semilunar valves stay open simultaneously at any time in a cardiac cycle of a normal person?
A. yes. B. no.
43. The QRS complex corresponds to ___.
A. ventricular repolarization. B. ventricular depolarization. C. atrial depolarization.
44. A patient's ECG displays 70 P waves but only 60 QRS complexes every minute, he likely has a ___.
A. first degree AV block. B. second degree AV block. C. third degree AV block..
45. If the end diastolic ventricular volume is 130 ml, the end systolic (after ejection) ventricular volume is 60 ml and the heart rate is 70 beat/min, the cardiac output will be ___.
A. 130 ml. B. 70 ml. C. 60 ml. D. 4,200 ml/min. E. 4,900 ml/min.
46. The Frank-Starling Law states that ___.
A. an increase in the afterload will increase cardiac output. B. an increase in contractility will increase cardiac output. C. an increase in the preload will increase cardiac output. D. a decrease in the afterload will increase cardiac output.
47. If a healthy man increases his heart rate from 200/min to 250/min, his cardiac output will most likely ___.
A. increase. B. decrease. C. remain unchanged.
48. When blood pressure increases suddenly, the baroreceptor reflex is expected to mediate ____.
A. a negative inotropic effect. B. a positive inotropic effect. C. a positive chronotropic effect
KEY
16C 17B 18D 19C 20E 21D 22B 23E 24B 25B 26C 27C 28E 29C 30B
31A 32D 33A 34A 35C 36E 37A 38B 39B 40A
41D 42B 43B 44B 45E 46C 47B 48A
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