CIRCULATORY DYNAMICS IN THE HUMAN
1. Blood flow in vessels follows the Poiseuille law. In a cylindrical tube with
pressure difference P1-P2, when the radius becomes one half, the flow reduces to
A. 1/2
B. 1/4
C. 1/8
D. 1/16
2. In flow dynamics, the resistance is defined as the ratio of pressure/flow.
Following the Poiseuille law, the resistance is a function of viscosity and the
geometric factors of the tube. What are the geometric factors of the tube?
A. Radius
B. Length
C. Number of tubes
D. All of above
3. In circulatory dynamics, relationship among mean arterial pressure, cardiac
output and total peripheral resistance follows the Poiseuille law. The mean
arterial pressure is the product of the cardiac output and the total peripheral
resistance. The cardiac output, in turn, is
A. the stroke volume
B. the product of heart rate and stroke volume
C. the ratio of stroke volume and heart rate
D. None of above
4. When a volume of blood, i.e., stroke volume, is pumped out of the ventricle
into the aorta, the pressure in the aorta will increase from the diastolic
pressure to the systolic pressure. This pressure increment is named as the pulse
pressure. The relationship between the stroke volume (V) and the pulse pressure
(P) is the arterial capacitance (C). What is the relationship?
A. P = V/C
B. P = VxC
C. None of above
5. Blood flow in human body is silent. When there are changes in the vessel
geometry or the blood property, turbulence may occur and generate the murmur.
Occurrence of turbulence depends on the Reynold's number. In general, when the
Reynold's number exceeds the critical value of approximately 2,000, turbulence
occurs. At a given vessel geometry, a low erythrocyte count, i.e., anemia, would
cause the Reynold's number
A. to increase
B. to decrease
C. unchanged
6. Before the blood reaches the capillary network, there are terminal arterioles
and precapillary sphincters, both containing one layer of smooth muscle
surrounding the endothelium. At quiescent conditions, most of capillaries are
closed. When there is an increase in the metabolic demand, the previously closed
capillaries are opened by relaxation of the terminal arterioles and the
precapillary sphincters.
A. This phenomenon is called recruitment.
B. The tissue becomes red.
C. The tissue becomes warmer.
D. all of above.
7. In capillaries, fluid filtration and reabsorption follow the Starling's
hypothesis. The rate of fluid filtration is a function of the filtration
coefficient and the pressure balance between the hydrostatic pressure and the
colloidal osmotic pressure. An increase in the capillary permeability favors
fluid filtration from
A. an increase in the filtration coefficient
B. a decrease in the reflection coefficient
C. All of above
D. None of above
8. Tissue edema is caused by an increase in fluid filtration or a decrease in
fluid reabsorption. Tissue edema can be caused by
A. arteriolar vasodilation
B. occlusion of veins
C. decrease in plasma protein concentration
D. All of above
9. Lymphatic obstruction causes tissue edema because of
A. an increase in the capillary pressure
B. a decrease in the colloidal osmotic pressure
C. an increase in the reflection coefficient
D. None of above
10. In the lung, the pulmonary capillary pressure is low and, therefore,
A. the low capillary pressure favors fluid reabsorption
B. the low interstitial pressure favors fluid filtration
C. the reflection coefficient is low
D. the lymphatic flow is high
11. If the systolic pressure is 118 mmHg and the diastolic pressure is 70 mmHg,
the mean arterial pressure is most likely to be
A. 102 mmHg
B. 94 mmHg
C. 86 mmHg
D. 78 mmHg
12. When the heart rate increases from 150/min to 250/min, the cardiac output
would
A. increase
B. decrease
C. be unchanged
13. The mean blood pressure is maintained constant in various pathophysiological
conditions. The monitoring is mediated by baroreceptors and chemoreceptors. The
baroreceptors are at the carotid sinus and the aortic arch. The chemoreceptors
are at the carotid bodies and the aortic bodies. When the blood pressure is
lowered, the nerve impulses from these receptors cause activation of the
sympathetic nerves and inhibition of the parasympathetic nerves, leading to
A. an increase in the heart rate
B. an increase in the cardiac contractility
C. an arteriolar vasoconstriction
D. a venular vasoconstriction
F. All of above
14. During the physical exercise, the blood pressure and cardiac output increase
significantly due to the sympathetic activation. The major input leading to the
sympathetic activation is
A. elevation of body temperature
B. hypoxia
C. acidosis
D. impulse from activation of the proprioceptors at joints and muscles
15. The veins are the major capacitance vessels because a small increment of
intravascular pressure results in a significant increase in the intravascular
volume. When a person lies down in a horizontal position, there is negligible
hydrostatic effect due to gravity on the venous pressure. When the person
assumes a standing position, the hydrostatic effect becomes significant and
A. the venous pressure in the foot may rise to 100 mmHg.
B. there will be a sudden venous blood pooling up to 500 ml.
C. there is a decrease in the venous return.
D. there is decreases in the stroke volume and the cardiac output.
F. there is a narrowing of the pulse pressure
G. All of above
16. Sympathetic nervous system is activated to mobilize the energy stores, to
increase the blood flow to vital organs and to exhibit the signs of alarm in
stressful situations, e.g.,
A. cold temperature
B. hemorrhage
C. hypoxia
D. trauma
E. emotional excitement
F. hypoglycemia
G. exercise
H. All of above