How does an increase in end-diastolic volume affect stroke volume according to Frank Starling Law?

According to the Frank-Starling Law of the Heart, an increase in end-diastolic volume (EDV) leads to an increased stroke volume (SV) up to a certain point. This relationship arises because as the heart fills with more blood during diastole, the myocardial fibers are stretched more. This greater stretch enhances the force of contraction during systole due to optimal alignment of actin and myosin filaments in cardiac muscle fibers.

When EDV increases, it allows the heart to pump a greater volume of blood. Thus, the stroke volume, which is the amount of blood ejected by the heart with each beat, typically increases as a direct response, illustrating the heart's ability to adjust its output based on the volume of incoming blood.

It's important to note that while the statement suggests that stroke volume doubles, in practical scenarios stroke volume will increase significantly but may not literally double due to limits of myocardial function and the physical characteristics of the heart. The underlying principle of the Frank-Starling mechanism is that increased filling volume enhances cardiac output efficiently, up to a physiological limit.