How do arteries supplying the leg muscles alter rate of blood flow through them during exercise?

Arteries supplying the leg muscles undergo several adaptations to alter the rate of blood flow during exercise:

Vasodilation: During exercise, the arteries supplying the leg muscles dilate (expand) to increase blood flow to the active muscles. This dilation is primarily mediated by local mechanisms, such as the release of nitric oxide (NO) and other vasodilators, in response to increased metabolic demands.

Recruitment of Precapillary Sphincters: Precapillary sphincters are small muscular structures located at the entrance of capillaries. During exercise, these sphincters relax, allowing more blood to enter the capillary network and perfuse the muscle tissues.

Increased Cardiac Output: As exercise intensity increases, the heart rate and cardiac output (the volume of blood pumped by the heart per minute) also increase. This rise in cardiac output contributes to the overall increase in blood flow to the leg muscles.

Sympathetic Nervous System Modulation: The sympathetic nervous system plays a role in regulating blood flow distribution during exercise. While sympathetic activity generally increases during exercise, the leg muscles experience a decrease in sympathetic vasoconstriction. This allows for more blood to be directed to the active muscles.

Metabolic Autoregulation: Metabolic autoregulation is a local mechanism that adjusts blood flow to match the metabolic demands of the tissue. As the leg muscles engage in more intense exercise, they produce more metabolic waste products, such as carbon dioxide and lactic acid. These waste products can cause local vasodilation, further increasing blood flow to the muscles.

Together, these mechanisms work in a coordinated manner to ensure that the leg muscles receive an adequate supply of oxygen and nutrients to support the increased energy demands during exercise.