Final answer:
During strenuous exercise, MAP usually increases despite the dilation of skeletal muscle arterioles because cardiac output significantly rises, counteracting the decrease in vascular resistance due to arteriole dilation.
Step-by-step explanation:
Effect of Strenuous Exercise on Mean Arterial Pressure (MAP):
During strenuous exercise, there are significant changes to the cardiovascular system, including alterations in MAP. When skeletal muscle arterioles dilate, which is necessary to meet the increased oxygen and nutrient demands of muscles during exercise, vascular resistance in these muscles decreases. However, overall MAP typically increases due to a rise in cardiac output—the amount of blood the heart pumps per minute—as both the heart rate and stroke volume increase.
The selective vasodilation in the arterioles of skeletal muscles, alongside systemic vasoconstriction in non-essential organs, ensures proper blood distribution to necessary areas during exercise. Moreover, venous return is enhanced due to venous compression from contracting skeletal muscles, known as the skeletal muscle pump effect. This contributes to a higher preload and more forceful cardiac contractions, further supporting the increase in cardiac output and subsequently the MAP.
While dilation of arterioles in the skeletal muscles alone would typically lead to a drop in resistance and potentially a lower MAP, the body's compensatory mechanisms during exercise - primarily the increase in cardiac output - result in an overall increase in MAP to maintain adequate blood flow throughout the body.