In hypovolemia, which compensatory mechanism is most likely to occur?

• A. Decreased heart rate
• B. Increased pulse rate
• C. Vasodilation
• D. Decreased sympathetic stimulation

Answer: (B)

When blood volume falls, arterial pressure drops and baroreceptors trigger a reflex increase in sympathetic nervous system activity. This boosts heart rate and causes peripheral vasoconstriction to preserve blood flow to vital organs. The most likely compensatory change is an increased pulse rate because rising heart rate helps maintain cardiac output despite a reduced stroke volume from hypovolemia. A slower heart rate would worsen perfusion, and vasodilation or reduced sympathetic activity would further lower blood pressure, making them unlikely responses in this situation.