Question

All of the following factors would be expected to increase stroke volume EXCEPT ________.

Group of answer choices

increased end diastolic volume

increased afterload

decreased end systolic volume

increased venous return

Answer 1

All of the following factors would be expected to increase stroke volume except increased afterload.

Explanation:

- Afterload is the pressure in the systemic circulation against which the left ventricle has to pump blood during ventricular systole. Thus, increased afterload decreases the stroke volume. A decrease in the afterload will increase the stroke volume.

- End diastolic volume (EDV) is the amount of blood remaining in the ventricle at the end of diastole. It is normally around 120 ml. An increased end diastolic volume increases the ventricular muscle wall stretching which in turn causes a stronger force of ventricular contraction during systole thus increasing the stroke volume.

- Stroke volume is the amount of blood pumped by the left ventricle into the systemic circulation ventricular systole. It is around 70 ml. Stroke volume can also be expressed as :- Stroke volume = end diastolic volume - end systolic volume. Thus, decreased end systolic volume increases the stroke volume.

- Venous return is the amount of blood returning back into the right atrium of the heart from systemic circulation through venous network. An increased venous return increases the preload which in turn increases the stroke volume. Preload is the amount of pressure on the ventricular musculature due to blood present in the ventricles just prior to ventricular systole at the end of diastolic phase.