The Frank–Starling mechanism
When venous return to the heart increases, stroke volume increases. Why?
Answer A: explanation for every choice
A
Correct. More filling stretches the sarcomeres toward a better overlap, so the ventricle contracts more forcefully.
B
Sympathetic effects are separate from this intrinsic mechanism.
C
Afterload is the pressure the ventricle must eject against and isn't lowered by more venous return.
D
Heart rate changes do not explain the Frank–Starling relationship.
TakeawayMore in → more out: preload stretch increases stroke volume.
Next question →
Reviewed 2026-11-05 by a medical student. Spot an error? Report it with question ID bb141.