Which cardiovascular change is commonly observed in dehydration as the body tries to maintain perfusion?

• A. Bradycardia
• B. Tachycardia
• C. Hypertension
• D. Decreased peripheral resistance

Answer: (B)

When the body is dehydrated, it must preserve blood flow to vital organs despite reduced circulating volume. Loss of plasma volume lowers venous return and stroke volume, which can drop cardiac output. To compensate, the body activates the baroreceptor reflex and the sympathetic system, increasing heart rate to maintain perfusion. This tendency toward a faster pulse—tachycardia—is the typical response. At the same time, vessels constrict to raise systemic vascular resistance, helping keep blood pressure from falling too low.

Bradycardia would worsen insufficient perfusion, and a rise in blood pressure (hypertension) isn’t the usual early response to dehydration. Decreased peripheral resistance would conflict with the vasoconstrictive compensation that supports perfusion.