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Chapter 30. The Heart as a Pump

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The second heart sound is caused by

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A. closure of the aortic and pulmonary valves.

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B. vibrations in the ventricular wall during systole.

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C. ventricular filling.

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D. closure of the mitral and tricuspid valves.

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E. retrograde flow in the vena cava.

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The correct answer is A. Closure of the aortic and pulmonary valves causes the characteristic second heart sound.

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The fourth heart sound is caused by

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A. closure of the aortic and pulmonary valves.

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B. vibrations in the ventricular wall during systole.

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C. ventricular filling.

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D. closure of the mitral and tricuspid valves.

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E. retrograde flow in the vena cava.

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The correct answer is C. Ventricular filling causes the fourth heart sound, which is due to either increased atrial pressure or stiffened ventricles.

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The dicrotic notch on the aortic pressure curve is caused by

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A. closure of the mitral valve.

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B. closure of the tricuspid valve.

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C. closure of the aortic valve.

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D. closure of the pulmonary valve.

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E. rapid filling of the left ventricle.

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The correct answer is C. The dicrotic notch is evident when vibrations occur due to closure of the aortic valve.

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During exercise, a man consumes 1.8 L of oxygen per minute. His arterial O2 content is 190 mL/L, and the O2 content of his mixed venous blood is 134 mL/L. His cardiac output is approximately

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A. 3.2 L/min.

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B. 16 L/min.

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C. 32 L/min.

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D. 54 L/min.

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E. 160 mL/min.

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The correct answer is C. O2 consumption/(Arterial-venous O2 content) = 1.8 L/min = 1800 ml/min/(190 − 134 ml/L) = 32 L/min.

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A 75 year old woman with a history of chronic congestive heart failure undergoes cardia catheterization t determine the extent of cardiac dysfunction. During estimation of systolic function, in what phase of ...

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