The self-regulating mechanism of the heart's blood pumping: the frank starling mechanism

2021-06-02 03:19 PM

Under different conditions, the amount of blood the heart pumps out per minute is usually determined mostly by the speed at which blood flows through the heart from the veins, which are the returning veins.

A person at rest, the heart only pumps about 4-6 litres of blood per minute. During exercise, the heart may have to pump four to seven times more blood than normal. This is because the pumping volume of the heart is regulated by (1) internal regulation of the heart in response to changes in the volume of blood flow into the heart and (2) regulation of the rate and force of contraction of the heart by the autonomic nervous system.

Under different conditions, the amount of blood the heart pumps out per minute is usually determined mostly by the speed at which blood flows through the heart from the veins, which are the returning veins. Each of the peripheral tissues of the body regulates the blood flow at home, and all the blood in the tissues combines and returns through the veins to empty into the atria.

The heart's ability to self-regulate to think with increased inflow is known as the Frank-Starling mechanism of the heart, in recognition of Otto Frank and Ernest Dtarling, two great physiologists of the heart. previous century. Basically, the Frank-Starling mechanism is understood that a lot of heart muscle is stretched during filling, a great deal of energy of contraction, and a very large amount of blood is pumped into the aorta. In other words: within physiological limits, the heart pumps all the blood back to itself through the venous route.

When more blood is added to the ventricles, the heart muscle is stretched. The stretch in turn causes the muscle to contract with increased contractility because the actin and myosin filaments are brought very close to the optimal position for strength formation. Thus, the ventricles automatically pump more blood into the arteries because of the increased pumping power.

The ability of the muscle to elongate, reaching an optimum strength to contract with increased muscle work, is characteristic of all skeletal muscles, and not unique to the heart muscle.

In addition, an important effect of dilated myocardium, which is still a factor in increasing cardiac pumping force as volume is increased. Stretching of the right atrial septum directly increases heart rate by 10-20%, which also increases the amount of blood pumped per minute, although it contributes very little compared to the Frank-Starling mechanism.