Question 1
During exercise, blood flow to the active skeletal muscles is increased by autoregulation. Propose a mechanism based on the need for nutrients that would explain how the autoregulation might take place.Question 2
Individuals with McArdle's disease cannot break down glycogen. How would this affect substrate utilization during exercise?Answer 1
When a skeletal muscle becomes more active, it has an increased demand for nutrients such as oxygen and glucose and quickly removes these from the surrounding interstitial fluid. This leaves fewer nutrients available for other cells that share the same interstitial fluid, such as the smooth muscle cells of the precapillary sphincter. As the available nutrients decline, energy production in the precapillary sphincters cannot keep pace with the need to keep the muscle in a contracted state, and the sphincters begin to relax. As they relax, the opening to the capillary becomes larger so that more blood flows into the capillary network that serves the skeletal muscle.Answer 2
These individuals cannot rely on glycogen stores during exercise. Therefore, carbohydrates are available to them through only two pathways: gluconeogenesis and glucose from the diet. As a result, they must rely mostly on fat β-oxidation for energy.