Question

During exercise, how/why does a larger percentage of blood (cardiac output) go to skeletal muscles?

Answer 1

There is a great increase in the amount of blood flowing to skeletal muscles during exercise. In resting
condition, the blood supply to the skeletal muscles is 3 to 4 mL/100 g of the muscle/minute. It increases up to 60 to 80 mL in moderate exercise and up to 90 to 120 mL in severe exercise.

.When any tissue becomes highly active, the rate of blood flow through the tissue increases . The increase in local metabolism causes the cells to devour tissue fluid nutrients rapidly and also to release large quantities of vasodilator substances. The result is dilation of local blood vessels and increased local blood flow. In this way, the active tissue receives the additional nutrients required to
sustain its new level of function.

During the muscular activity, stoppage of blood flow occurs when the muscles contract. It is because of compression of blood vessels during contraction. And in between the contractions, the blood flow increases. It is due to the sympathetic activity. Sympathetic nerves cause vasodilatation in muscles. The sympathetic nerve fibers causing vasodilatation in skeletal muscle are called sympathetic cholinergic fibers since these fibers secrete acetylcholine instead of noradrenaline