In the context of stroke volume, what does increased venous return promote?

Increased venous return directly influences stroke volume by augmenting the volume of blood that fills the ventricles during diastole, a phenomenon known as preload. When more blood returns to the heart through the veins, the ventricles stretch to accommodate this extra volume, leading to a more forceful contraction during systole, thanks to the Frank-Starling mechanism. This principle states that the greater the stretch of cardiac muscle fibers within physiological limits, the stronger the force of contraction will be. Consequently, with increased venous return, the heart can pump out a larger volume of blood with each heartbeat, effectively increasing stroke volume. This relationship is a key aspect of cardiac physiology, illustrating how the heart adapts to changes in blood volume and flow dynamics.