During exercise, cardiac output increases dramatically, but mean ...

[viki]

During exercise, cardiac output increases dramatically, but mean arterial blood pressure rises very little. Why is this so?
 
  a. Venules constrict, increasing vascular re-sistance.
  b. Arterioles dilate, decreasing vascular ca-pacity.
  c. Arterioles constrict, increasing vascular resistance.
  d. Muscle vessels dilate, increasing vascular capacity.

Question 2

Mean arterial blood pressure can be regulated by changing which of the following? 1. Capacity of the circulatory system 2. Effective volume of circulating blood 3. Tone of the capacitance vessels (veins)
 
  a. 1 and 2 only
  b. 2 only
  c. 1, 2, and 3
  d. 3 only

[chem1s3]

Answer to Question 1

ANS: D
For example, when exercising, the circulating blood volume undergoes a relative increase, but blood pressure remains near normal. This is because the skeletal muscle vascular beds dilate, causing a large increase in system capacity.

Answer to Question 2

ANS: C
All else being constant, mean arterial pressure is directly related to the volume of blood in the vascular system and inversely related to its capacity. A change in the tone of the capacitance vessels alters their capacity.
Mean arterial pressure = volume/capacity.