Question

For each of the physiological characteristics A–E, select the most appropriate option from the special circulations listed below. 

1. Coronary blood flow. 

2. Skeletal muscle blood flow. 

3. Splanchnic blood flow. 

4. Cerebral blood flow. 

5. Skin blood flow. 

A. Increases during sweating. 

B. Greater during diastole than during systole. 

C. Passes through a portal circulation. 

D. Affected mainly by the P_CO2 level in the blood. 

E. Increases during fainting.

Answer 1

A. Option 5 Skin blood flow. Skin blood flow increases during sweating due to an active sympathetic cholinergic mechanism. 

B. Option 1 Coronary blood flow. Coronary blood flow is decreased during systole because of compression of the vessels by the contracting ventricular myocardium. 

C. Option 3 Splanchnic blood flow. Splanchnic blood flow passes through two capillary beds in one circuit of the circulation, firstly through the capillaries in the alimentary tract and then through a portal capillary bed in the liver. 

D. Option 4 Cerebral blood flow. Cerebral blood flow is little affected by cardiovascular reflexes. However it is very sensitive to changes in the P_CO2 of the perfusing blood. 

E. Option 2 Skeletal muscle blood flow. Vasodilatation in skeletal muscle during fainting causes a large fall in peripheral resistance and is one of the factors leading to the fall in arterial pressure that results in the faint.