232
CARDIOVASCULAR PHYSIOLOGY CONCEPTS
14.0 L/min (i.e., it more than doubled).
Choice “c” is incorrect because stroke
volume increased by 25% (from 80 to
100 mL/beat), and the ejection fraction
increased by 25% (from 60% to 75%).
Therefore, end-diastolic volume could
not have changed because ejection
fraction equals stroke volume divided
by end-diastolic volume. Choice “d” is
incorrect because the percent change
in cardiac output is much greater than
the percent change in arterial pressure;
the systemic vascular resistance can be
approximated from the arterial pressure
divided by the cardiac output.
4.
The correct answer is “d” because
activation of the renin-angiotensin-
aldosterone system during pregnancy
increases blood volume. Choice “a”
is incorrect because systemic vascular
resistance decreases during pregnancy
owing to the developing uterine circula-
tion. Choices “b” and “c” are incorrect
because heart rate and cardiac output
increase during pregnancy.
5.
The correct answer is “a” because the
baroreceptor reflex activates sympathetic
adrenergic nerves that constrict arte-
rial and venous vessels. Choice “b” is
incorrect because sympathetic activation
increases systemic vascular resistance.
Choice “c” is incorrect because sympa-
thetic activation is accompanied by with-
drawal of vagal tone on the heart. Choice
“d” is incorrect because renin, not angio-
tensin II, is released from the kidneys.
6.
The correct answer is “d” because
long-term recovery from hypovolemia
requires renal retention of water, which
is partially regulated by vasopres-
sin. Choice “a” is incorrect because
increased renin release and subsequent
formation of angiotensin II and aldo-
sterone contribute to renal reabsorp-
tion of sodium and water. Choice “b” is
incorrect because sodium reabsorption,
not loss, is enhanced following hemor-
rhage. Choice “c” is incorrect because
increased capillary fluid filtration would
decrease blood volume and not serve as
a compensatory mechanism following
hemorrhage.
7. The correct answer is “c” because
reduced oxygen delivery to the periph-
eral organs stimulates anaerobic metabo-
lism, leading to metabolic acidosis,
which impairs cardiac contraction.
Choices “a,” “b,” and “d” are incorrect
because these are normal compensatory
mechanisms that help to maintain arte-
rial pressure following hemorrhage.
8. The correct answer is “d” because either
hypothyroidism or hyperthyroidism can
cause hypertension. Choices “a,” “b,”
and “c” are incorrect because each of
these can decrease blood volume, which
would decrease arterial pressure.
9. The correct answer is “b” because dia-
stolic dysfunction caused by decreased
ventricular compliance (choice “a” is
therefore incorrect) leads to an elevated
end-diastolic pressure at any given end-
diastolic volume. Choice “c” is incorrect
because changes in end-systolic volume
are normally associated with changes in
systolic function. Choice “d” is incor-
rect because ejection fraction does not
necessarily change much with diastolic
dysfunction because reduced stroke vol-
ume is usually associated with reduced
end-diastolic volume.
10. The correct answer is “a” because car-
diac output is unable to increase suf-
ficiently to maintain arterial pressure as
systemic vascular resistance falls during
exercise. Choice “b” is incorrect because
reduced organ perfusion increases oxy-
gen extraction from the arterial blood.
Choice “c” is incorrect because impaired
inotropic responses during exercise
reduce ejection fraction. Choice “d”
is incorrect because the heart failure
patient achieves lower maximal oxygen
consumption because maximal cardiac
output is reduced.
11. The correct answer is “c” because reduc-
ing afterload increases stroke volume
and reduces ventricular end-diastolic
volume; these changes enhance ejection
fraction. Choice “a” is incorrect because
previous page 245 Cardiovascular Physiology Concepts  2nd Edition read online next page 247 Cardiovascular Physiology Concepts  2nd Edition read online Home Toggle text on/off