Please explain staling`s law in blood circulatory system.

Dear student

1. During Diastole the ventricles fill to a volume called as End diastolic Volume(EDV).
2. The heart does not eject all the blood it contains during systole. A small volume of blood which remains behind after contraction of ventricles is known as End Systolic Volume (ESV).
3. Important point to understand is that stroke volume which is volume of blood ejected during a systole can be equated as : EDV- ESV. A normal SV is 70 ml.
4. An increase in SV occurs when EDV is increased or ESV decreases.
5. The more cardiac muscle is stretched within physiological limits, the more Forcibly it will contract. So, Increasing volumes of blood in ventricles i.e. EDV, increase the stretch in cardiac muscles fibres & thus the Force generated by ventricular wall contraction.
6. Greater stretch means more blood volume is pumped out ( increase in Stroke Volume), up to physical limits.
7. To summarize: More EDV- more Stretch in Cardiac Muscle- More Force of contraction in myocardium- More stroke volume.