Which will NOT occur if blood pressure drops below homeostatic levels?

Which will NOT occur if blood pressure drops below homeostatic levels?

• A. Cardiac output will increase.
• B. Heart rate will decrease.
• C. Systemic vascular resistance will rise.
• D. Peripheral perfusion is reduced.

Answer: (A)

When blood pressure falls, the body activates the baroreceptor reflex to restore pressure. This reflex raises sympathetic outflow, which increases heart rate and the force of heart contraction, and causes arteriolar constriction. The net effect is an increase in cardiac output and a rise in systemic vascular resistance. Blood is also redistributed so that perfusion to nonessential tissues decreases, while core organs are kept as a priority. From this perspective, the direction of the heart rate change is clear: heart rate does not drop; it tends to rise to support cardiac output. So a decrease in heart rate would not occur during hypotension. The other responses described—systemic vascular resistance rising and peripheral perfusion being reduced to protect vital organs—are consistent with the compensatory mechanism. Cardiac output would typically be maintained or increased due to the increased heart rate and contractility.

When blood pressure falls, the body activates the baroreceptor reflex to restore pressure. This reflex raises sympathetic outflow, which increases heart rate and the force of heart contraction, and causes arteriolar constriction. The net effect is an increase in cardiac output and a rise in systemic vascular resistance. Blood is also redistributed so that perfusion to nonessential tissues decreases, while core organs are kept as a priority.

From this perspective, the direction of the heart rate change is clear: heart rate does not drop; it tends to rise to support cardiac output. So a decrease in heart rate would not occur during hypotension. The other responses described—systemic vascular resistance rising and peripheral perfusion being reduced to protect vital organs—are consistent with the compensatory mechanism. Cardiac output would typically be maintained or increased due to the increased heart rate and contractility.