Cardiac Output, Blood Flow, and Blood Pressure 491
- Total blood flow in the cerebral circulation
a. varies with systemic arterial pressure.
b. is regulated primarily by the sympathetic system.
c. is maintained constant within physiological limits.
d. increases significantly during exercise.
- Which of these organs is able to tolerate the greatest
reduction in blood flow?
a. Brain c. Skeletal muscles
b. Heart d. Skin
- Which of these statements about arteriovenous shunts in the
skin is true?
a. They divert blood to superficial capillary loops.
b. They are closed when the ambient temperature is very low.
c. They are closed when the deep-body temperature rises
much above 37 8 C.
d. All of these are true.
- An increase in blood volume will cause
a. a decrease in ADH secretion.
b. an increase in Na^1 excretion in the urine.
c. a decrease in renin secretion.
d. all of these.
- The volume of blood pumped per minute by the left ventricle is
a. greater than the volume pumped by the right ventricle.
b. less than the volume pumped by the right ventricle.
c. the same as the volume pumped by the right ventricle.
d. either less or greater than the volume pumped by the right
ventricle, depending on the strength of contraction.
- Blood pressure is lowest in
a. arteries. d. venules.
b. arterioles. e. veins.
c. capillaries.
- Stretch receptors in the aortic arch and carotid sinus
a. stimulate secretion of atrial natriuretic peptide.
b. serve as baroreceptors that affect activity of the vagus and
sympathetic nerves.
c. serve as osmoreceptors that stimulate the release of ADH.
d. stimulate renin secretion, thus increasing angiotensin II
formation.
- Angiotensin II
a. stimulates vasoconstriction.
b. stimulates the adrenal cortex to secrete aldosterone.
c. inhibits the action of bradykinin.
d. does all of these.
- Which of these is a paracrine regulator that stimulates
vasoconstriction?
a. Nitric oxide c. Bradykinin
b. Prostacyclin d. Endothelin-1
20. The pulse pressure is a measure of
a. the number of heartbeats per minute.
b. the sum of the diastolic and systolic pressures.
c. the difference between the systolic and diastolic
pressures.
d. the difference between the arterial and venous pressures.
Test Your Understanding
- Define the terms contractility, preload, and afterload, and
explain how these factors affect the cardiac output.
- Using the Frank-Starling law of the heart, explain how
the stroke volume is affected by (a) bradycardia and (b) a
“missed beat.”
- Which part of the cardiovascular system contains the most
blood? Which part provides the greatest resistance to blood
flow? Which part provides the greatest cross-sectional area?
Explain.
- Explain how the kidneys regulate blood volume.
- A person who is dehydrated drinks more and urinates less.
Explain the mechanisms involved.
- Using Poiseuille’s law, explain how arterial blood flow can
be diverted from one organ system to another.
- Describe the mechanisms that increase the cardiac output
during exercise and that increase the rate of blood flow to
the heart and skeletal muscles.
- Explain why an anxious person may have cold, clammy skin
and why the skin becomes hot and flushed on a hot, humid
day.
- Explain the different ways in which a drug that acts as an
inhibitor of angiotensin-converting enzyme (ACE) can lower
the blood pressure. Also, explain how diuretics and
b 1 -adrenergic-blocking drugs work to lower the blood pressure.
- Explain how hypotension may be produced in (a)
hypovolemic shock and (b) septic shock. Also, explain the
mechanisms whereby people in shock have a rapid but weak
pulse, cold and clammy skin, and low urine output.
- Describe the mechanisms that have been proposed to explain
how a diet high in salt could raise the blood pressure.
- Explain how immersion of the body in water causes an
increased volume of urine.
Test Your Analytical Ability
- One consequence of the Frank-Starling law of the heart is
that the outputs of the right and left ventricles are matched.
Explain why this is important and how this matching is
accomplished.
- An elderly man who is taking digoxin for a weak heart
complains that his feet hurt. Upon examination, his feet are
found to be swollen and discolored, with purple splotches
and expanded veins. He is told to keep his feet raised and is
given a prescription for Lasix, a powerful diuretic. Discuss
this man’s condition and the rationale for his treatment.
