520 SECTION VICardiovascular Physiology
CHAPTER SUMMARY
■ Blood flows into the atria and then the ventricles of the heart
during diastole and atrial systole, and is ejected during systole
when the ventricles contract and pressure exceeds the pressures
in the pulmonary artery and aorta.
■ Careful timing of the opening and closing of the atrioventricular
(AV), pulmonary, and aortic valves allows blood to move in an ap-
propriate direction through the heart with minimal regurgitation.
■ The proportion of blood leaving the ventricles in each cardiac
cycle is called the ejection fraction and is a sensitive indicator of
cardiac health.
■ The arterial pulse represents a pressure wave set up when blood is
forced into the aorta; it travels much faster than the blood itself.
■ Heart sounds reflect the normal vibrations set up by abrupt
valve closures; heart murmurs can arise from abnormal flow
often (although not exclusively) caused by diseased valves.
■ Changes in cardiac output reflect variations in heart rate, stroke
volume, or both; these are controlled, in turn, by neural and hor-
monal input to cardiac myocytes.
■ Cardiac output is strikingly increased during exercise.
■ In heart failure, the ejection fraction of the heart is reduced due
to impaired contractility in systole or reduced filling during
diastole; this results in inadequate blood supplies to meet the
body’s needs. Initially, this is manifested only during exercise,
but eventually the heart will not be able to supply sufficient
blood flow even at rest.MULTIPLE-CHOICE QUESTIONS
For all questions, select the single best answer unless otherwise directed.
- 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 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.
3. 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.
4. During exercise, a man consumes 1.8 L of oxygen per minute.
His arterial O 2 content is 190 mL/L, and the O 2 content of his
mixed venous blood is 134 mL/L. His cardiac output is approxi-
mately
A) 3.2 L/min.
B) 16 L/min.
C) 32 L/min.
D) 54 L/min.
E) 160 mL/min.
5. The work performed by the left ventricle is substantially greater
than that performed by the right ventricle, because in the left
ventricle
A) the contraction is slower.
B) the wall is thicker.
C) the stroke volume is greater.
D) the preload is greater.
E) the afterload is greater.
6. Starling’s law of the heart
A) does not operate in the failing heart.
B) does not operate during exercise.
C) explains the increase in heart rate produced by exercise.
D) explains the increase in cardiac output that occurs when
venous return is increased.
E) explains the increase in cardiac output when the sympa-
thetic nerves supplying the heart are stimulated.
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