What does the Frank-Starling law state?

The Frank-Starling law of the heart, also known as the Starling's law, asserts that the stroke volume of the heart increases in response to an increase in the volume of blood filling the heart, known as preload. This physiological principle highlights the relationship between the degree of stretch of the heart muscle fibers and their ability to contract. When the heart is filled with more blood during diastole, the myocardial fibers are stretched more than usual, which enhances the force of contraction during systole, ultimately resulting in an increased stroke volume.

This process is critical for maintaining efficient blood circulation in response to varying bodily demands. For example, during physical activity, increased venous return due to muscle contractions leads to more blood in the heart, optimizing stroke volume and ensuring that the body receives adequate oxygen and nutrients.

In contrast, other statements do not accurately represent this key cardiac principle. While heart rate can influence overall cardiac output, the Frank-Starling mechanism specifically relates to the effects of preload on stroke volume, independent of heart rate.