440
Chapter 12
12. When a person engages in strenuous, prolonged exercise
a. blood fl ow to the kidneys is reduced.
b. cardiac output is reduced.
c. total peripheral resistance increases.
d. systolic arterial blood pressure is reduced.
e. blood fl ow to the brain is reduced.
13. Hematocrit is increased
a. when a person has a vitamin B
12
defi ciency.
b. by an increase in secretion of erythropoietin.
c. when the number of white blood cells is increased.
d. following a hemorrhage.
e. in response to excess oxygen delivery to the kidneys.
14. The principal site of erythrocyte production is
a. the liver.
b. the kidneys.
c. the bone marrow.
d. the spleen.
e. the lymph nodes.
15. Which is
not
part of the cascade leading to formation of a
blood clot?
a. contact between the blood and collagen found outside the
blood vessels
b. prothrombin converted to thrombin
c. formation of a stabilized fi brin mesh
d. activated platelets
e. secretion of tissue plasminogen activator (t-PA) by
endothelial cells
Chapter 12 Quantitative and Thought Questions
(Answers appear in Appendix A.)
1. A person is found to have a hematocrit of 35 percent. Can you
conclude that there is a decreased volume of erythrocytes in the
blood?
2. Which would cause a greater increase in resistance to fl ow, a
doubling of blood viscosity or a halving of tube radius?
3. If all plasma membrane calcium channels in contractile cardiac
muscle cells were blocked with a drug, what would happen to
the muscle’s action potentials and contraction?
4. A person with a heart rate of 40 has no P waves but normal
QRS complexes on the ECG. What is the explanation?
5. A person has a left ventricular systolic pressure of 180 mmHg
and an aortic systolic pressure of 110 mmHg. What is the
explanation?
6. A person has a left atrial pressure of 20 mmHg and a left
ventricular pressure of 5 mmHg during ventricular fi lling.
What is the explanation?
7. A patient is taking a drug that blocks beta-adrenergic receptors.
What changes in cardiac function will the drug cause?
8. What is the mean arterial pressure in a person whose systolic
and diastolic pressures are, respectively, 160 and 100 mmHg?
9. A person is given a drug that doubles the blood fl ow to her
kidneys but does not change the mean arterial pressure. What
must the drug be doing?
10. A blood vessel removed from an experimental animal dilates
when exposed to acetylcholine. After the endothelium is
scraped from the lumen of the vessel, it no longer dilates in
response to this mediator. Explain.
11. A person is accumulating edema throughout the body. Average
capillary pressure is 25 mmHg, and lymphatic function is
normal. What is the most likely cause of the edema?
12. A person’s cardiac output is 7 L/min and mean arterial pressure
is 140 mmHg. What is the person’s total peripheral resistance?
13. The following data are obtained for an experimental animal
before and after administration of a drug. Before: Heart rate
= 80 beats/min, stroke volume = 80 ml/beat. After: Heart
rate = 100 beats/min, and stroke volume = 64 ml/beat. Total
peripheral resistance remains unchanged. What has the drug
done to mean arterial pressure?
14. When the nerves from all the arterial baroreceptors are cut in an
experimental animal, what happens to mean arterial pressure?
15. What happens to the hematocrit within several hours after a
hemorrhage?
Chapter 12 Answers to Physiological Inquiries
Figure 12–1
The hematocrit would be 33 percent because the
red blood cell volume is the difference between total blood
volume and plasma volume (4.5 – 3.0 = 1.5 L), and hematocrit
is determined by the fraction of whole blood that is red blood
cells (1.5 L /4.5 L = 0.33, or 33 percent).
Figure 12–5
No, the fl ow on side B would be less. The summed
wall area causing friction would be the same in both sides.
The formula for circumference of a circle is 2
π
r
, so the wall
circumference in side A would be 2
×
3.14
×
2 = 12.56, and for
the two tubes on side B it would be (2
×
3.14
×
1) +
( 2
×
3.14
×
1) = 12.56. However, the total cross section
through which fl ow occurs would be larger in side A than in
side B. The formula for cross-sectional area of a circle is
π
r
2
,
so the area of side A would be 3.14
×
2
2
= 12.56, whereas the
summed area of the tubes in side B would be (3.14
×
1
2
) +
(3.14
×
1
2
) = 6.28. Thus, even with two outfl ow tubes on side
B, there would be more fl ow through side A.
Figure 12–8
A: If this diagram included a systemic portal vessel,
the order of structures in the lower box would be: aorta
arteries
arterioles
capillaries
venules
portal vessel
capillaries
venules
veins
vena cava. Examples of portal
vessels include the hepatic portal vein, which carries blood from
the intestines to the liver (Chapter 15), and the hypothalamo-
pituitary portal vessels (Figure 11–12).
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