45. Which of the following lists the elements of the heart\'s comduction in the

Question

45. Which of the following lists the elements of the heart's comduction in the correct sequence? SA node, AV bundle, bundle branches, AV node, Purkinje fibers b. a. AV node, SA node, AV bundle, bundle branches, Purkinje fibers Purkinje fibers, AV bundle, bundle branches, AV node, SA node d. c. SA node, AV bundle, AV node, bundle branches, Purkinje fibers e. SA node, AV node, AV bundle, bundle branches, Purkinje fibers 46. Increased stimulation of the heart by the cardioacceleratory center causes a. stimulation by ACh of muscarinic receptors on the SA node and cardiac muscle fibers of the ventricles stimulation by norepinephrine of the SA node and of the beta receptors on the cardiac muscle fibers of the ventricles stimulation by norepinephrine of the SA node but no effect on the cardiac muscle fibers of the ventricles b. c. d. stimulation by ACh of nicotinic receptors on the SA node and cardiac muscle fibers of the ventricles stimulation by norepinephrine of the SA node and of the alpha receptors on the cardiac muscle fibers of the ventricles e. 47. During the cardiac cycle: a. P wave of the EKG occurs between the first and second heart sounds b. QRS complex of the EKG precedes the increase in ventricular pressure c. first heart sound occurs during atrial systole d. second heart sound coincides with the QRS complex of the EKG 48. Angina pectoris is: a. an embryonic structure that develops into the aorta b. pain accompanying myocardial ischemia c· the heart's location within the mediastinum d. part of the cardiac conduction system e. the covering of the heart 49. The term afterload refers to: a. the pressure that must be overcome before semilunar valves can open b. the pressure in blood vessels necessary to cause the semilunar valves to close c. the maximum possible cardiac output above resting cardiac output d. end-diastolic volume e. end-systolic volume 50. On an EKG, depolarization of the atria is represented by the: a. P wave b. T wave d. P-Q interval e. S-T segment c. QRS complex

Explanation / Answer

45.- E ( SA NODE , AV NODE , AV BUNDLE , BUNDLE BRANCHES , PURKINJIE FIBERS

46- B ( STIMULATION BY NONEPINEPHRINE OF SA NODE AND BETA RECEPTOR ON THE CARDIAC MUSCLE FIBERS OF THE VENTRICLES)

47.- B (QRS COMPLEX OF EKG PRECEDES THE INCREASE IN VENTRICULAR PRESSURE)

48.- B (PAIN ACCOMPANYING MYOCARDIAL ISCHEMIA)

49.- A (THE PRESSURE THAT MUST BE OVERCOME BEFORE SEMILUNAR VALVES CAN OPEN)

50.- A (P WAVE)

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