Question

As your muscles contract during activity, more blood is returned to the heart. Which variable would be affected and what would be the outcome of this action?

A) end systolic volume would be increased, which would increase cardiac output
B) prelude would be increase, which would increase cardiac output
C) contractility would be increased, which would increase cardiac output
D) after load would increase, which woulds increase cardiac output

Answer 1

An increased venous return during muscle activity enhances the preload, leading to a stronger cardiac contraction and increased cardiac output, as explained by the Frank-Starling principle.

Step-by-step explanation:

As your muscles contract during activity and more blood is returned to the heart, the variable that would be affected is preload, which refers to the initial stretching of the cardiac muscle cells prior to contraction. An increased preload leads to a more forceful contraction according to the Frank-Starling principle. Therefore, the correct answer to the question is B) preload would be increased, which would increase cardiac output.

During activity, as the muscles contract, more blood is returned to the heart. This increased blood flow leads to an increase in preload, which is the stretch on the ventricles prior to contraction. In turn, this increase in preload enhances the force of contraction of the cardiac muscle, increasing contractility. The outcome of this action is an increase in stroke volume and ultimately an increase in cardiac output.