In response to dehydration, what would help maintain cardiac output?

• A. A decrease in heart rate
• B. An increase in stroke volume
• C. A decrease in stroke volume
• D. An increase in heart rate

Answer: (D)

In response to dehydration, the body attempts to maintain blood volume and cardiac output, which is crucial for ensuring that organs receive sufficient oxygen and nutrients. Dehydration leads to a decrease in blood volume due to loss of fluids, which can reduce blood pressure and make it more difficult for the heart to pump enough blood.

An increase in heart rate is a compensatory mechanism that helps to maintain cardiac output despite a decrease in blood volume. While stroke volume may decrease due to reduced blood volume, the body can increase heart rate to help counteract this reduction. By increasing heart rate, the heart can increase the frequency of contractions, thus helping to maintain overall blood flow and support adequate perfusion of tissues.

This response aligns with the body's physiological adaptations under stress, as the sympathetic nervous system would activate to increase heart rate (through the release of catecholamines), thereby helping maintain cardiac output even when stroke volume may be compromised due to dehydration.