What happens to stroke volume as venous return increases, according to Starling's law?

According to Starling's law of the heart, stroke volume increases as venous return increases, up to a certain point. This principle explains how the heart's ability to pump blood more effectively is directly related to the volume of blood filling the ventricles before contraction, known as preload.

As venous return increases, it leads to an increased end-diastolic volume, which stretches the cardiac myocardium. This stretching of the heart muscle fibers results in a better alignment of the contractile proteins (actin and myosin), enhancing the force of contraction during systole. Therefore, with increased venous return, there is a corresponding increase in stroke volume as more blood is pushed out of the heart with each beat.

This relationship holds as long as the heart is functioning normally and within physiological limits. However, if the volume exceeds a certain threshold, the heart may not be able to continue effectively increasing stroke volume, but this is not typically seen within normal physiological ranges described by Starling's law.