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Chapter 30. The Heart as a Pump

The second heart sound is caused by

A. closure of the aortic and pulmonary valves.

B. vibrations in the ventricular wall during systole.

C. ventricular filling.

D. closure of the mitral and tricuspid valves.

E. retrograde flow in the vena cava.

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

The fourth heart sound is caused by

A. closure of the aortic and pulmonary valves.

B. vibrations in the ventricular wall during systole.

C. ventricular filling.

D. closure of the mitral and tricuspid valves.

E. retrograde flow in the vena cava.

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

The dicrotic notch on the aortic pressure curve is caused by

A. closure of the mitral valve.

B. closure of the tricuspid valve.

C. closure of the aortic valve.

D. closure of the pulmonary valve.

E. rapid filling of the left ventricle.

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

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

A. 3.2 L/min.

B. 16 L/min.

C. 32 L/min.

D. 54 L/min.

E. 160 mL/min.

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.

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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