Which statement best describes the Frank-Starling mechanism?

Which statement best describes the Frank-Starling mechanism?

• A. An increase in end-diastolic volume leads to greater stretch of the heart muscle and a stronger contraction, increasing stroke volume.
• B. An increase in end-diastolic volume leads to decreased stroke volume.
• C. End-diastolic volume has no effect on stroke volume.
• D. End-diastolic volume increases afterload.

Answer: (A)

The Frank-Starling mechanism shows how the heart adjusts its force of contraction based on how much it is filled. When more blood returns to the ventricle, the end-diastolic volume increases, which stretches the cardiac muscle fibers to a longer length. This stretch moves the sarcomeres toward an optimal length for interaction between actin and myosin, so the heart can generate a stronger contraction during systole. The result is a higher stroke volume, helping the heart pump out the amount of blood that returned to it and keeping cardiac output in balance with venous return. In short, more filling → greater stretch → stronger heartbeat → larger stroke volume. The other ideas don’t fit this relationship: increasing EDV does not reduce stroke volume, EDV does influence stroke volume, and EDV is about preload, not a change in afterload.

The Frank-Starling mechanism shows how the heart adjusts its force of contraction based on how much it is filled. When more blood returns to the ventricle, the end-diastolic volume increases, which stretches the cardiac muscle fibers to a longer length. This stretch moves the sarcomeres toward an optimal length for interaction between actin and myosin, so the heart can generate a stronger contraction during systole. The result is a higher stroke volume, helping the heart pump out the amount of blood that returned to it and keeping cardiac output in balance with venous return. In short, more filling → greater stretch → stronger heartbeat → larger stroke volume. The other ideas don’t fit this relationship: increasing EDV does not reduce stroke volume, EDV does influence stroke volume, and EDV is about preload, not a change in afterload.