According to the Frank-Starling law of the heart: A. At lower end diastolic volu

Question

According to the Frank-Starling law of the heart:

A. At lower end diastolic volumes, stroke volume will increase due to more overlap of actin and myosin and more forceful contractions

B. If end diastolic volume increases, stroke volume will increase proportionately due to optimal overlap of actin and myosin

C. The shorter the initial length of the cardiac muscle fibers prior to contraction the more forceful will be the subsequent contraction

D. As cardiac output is reduced, blood pools in the veins so that arterial blood pressure increases and venous return increases

My choice is between B or D, not sure which one.

Explanation / Answer

Ans.

The choice is (B).

According to Frank- Starling law of the heart if end diastolic volume increases, stroke volume will increase proportionately due to optimal overlap of actin and myosin.

According to Frank Starling law, stroke volume of heart increases with increase in the volume of blood in the ventricles before contraction. Volume of blood in the ventricles before contraction is called as End Diastolic Volume. When volume of blood is more in ventricles then it stretches the muscle fibres of ventricles more and due to which force of contraction of muscle fibres of ventricles increases which leads to increased stroke volume. When muscles fibres are stretched, active tension is created due to overlap of actin and myosin filaments. The importance of this law is that there is always equality between right and left ventricular stroke volume.

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