If dehydration occurs, what is likely to happen to stroke volume?

• A. It remains unchanged
• B. It increases
• C. It decreases
• D. It fluctuates greatly

Answer: (C)

When dehydration occurs, the overall volume of blood in the body decreases due to the loss of fluids. This reduction in blood volume leads to a decrease in venous return, which is the amount of blood returning to the heart. As a result, the filling of the heart's ventricles during diastole is compromised, leading to a lower end-diastolic volume.

Stroke volume, defined as the amount of blood ejected by the heart with each beat, depends significantly on this end-diastolic volume. When venous return is decreased due to dehydration, the stroke volume consequently decreases as well. Lower stroke volume can lead to a compensatory increase in heart rate to maintain cardiac output, but the original question focuses specifically on the direct impact of dehydration on stroke volume, making it clear that dehydration leads to a decrease in stroke volume.

Understanding the relationship between blood volume, venous return, and stroke volume is crucial in grasping how dehydration affects cardiac function.