Question

Under which of the following conditions is there most likely to be an increase in stroke volume?

A. Moving from the supine posture to the standing posture

B. An increase in sympathetic efferent nerve activity to the heart

C. When there is widespread systemic vasoconstriction

d. When there is venoconstriction

Answer 1

B. An increase in sympathetic efferent nerve activity to the heart

Explanation:

- An increase in sympathetic activity to the heart results in increase in myocardial contractility, resulting in more forcefull ejection of the blood through ventricles causing increase i stroke volume

- Moving from supine to standing posture would result in pooling of the blood in the lower extremities, resulting in decrease in venous return that in turn reduces the stroke volume.

- vasoconstriction increases afterload, resisting the blood flow, thus decreasing the stroke volume.