Which mechanism increases vascular resistance during exercise, contributing to higher blood pressure?

Which mechanism increases vascular resistance during exercise, contributing to higher blood pressure?

• A. Vasodilation reduces resistance
• B. Dehydration is the primary cause of increased BP
• C. Increased heart rate alone raises BP without resistance change
• D. Vasoconstriction increases vascular resistance

Answer: (D)

Vascular resistance rises when arterioles constrict, increasing the force against which the heart has to pump. During exercise, the sympathetic nervous system stimulates smooth muscle in many arteries to constrict (vasoconstriction) in nonworking areas, which raises systemic vascular resistance. At the same time, blood flow is directed to active muscles where local factors cause vasodilation, but the overall effect is that systemic vascular resistance increases enough to contribute to higher blood pressure as cardiac output also rises. Vasodilation would lower resistance, so it wouldn’t explain the BP rise. Dehydration affects volume status rather than the immediate resistance in the vessels during exercise. An increased heart rate raises blood pressure mainly by increasing cardiac output, not by changing vascular resistance, so the mechanism responsible for the resistance increase is vasoconstriction.

Vascular resistance rises when arterioles constrict, increasing the force against which the heart has to pump. During exercise, the sympathetic nervous system stimulates smooth muscle in many arteries to constrict (vasoconstriction) in nonworking areas, which raises systemic vascular resistance. At the same time, blood flow is directed to active muscles where local factors cause vasodilation, but the overall effect is that systemic vascular resistance increases enough to contribute to higher blood pressure as cardiac output also rises.

Vasodilation would lower resistance, so it wouldn’t explain the BP rise. Dehydration affects volume status rather than the immediate resistance in the vessels during exercise. An increased heart rate raises blood pressure mainly by increasing cardiac output, not by changing vascular resistance, so the mechanism responsible for the resistance increase is vasoconstriction.