OSMT (Ontario Society of Medical Technologists) Practice Exam

Increased blood flow within a muscle during exercise primarily occurs due to vasodilatation. This physiological response involves the widening of blood vessels, which allows for a greater volume of blood to flow through the muscle tissues. When you exercise, the metabolic demands of the muscles increase, calling for a higher supply of oxygen and nutrients while also requiring the removal of metabolic waste products, like carbon dioxide and lactic acid.

The release of various local factors, such as adenosine and nitric oxide, during physical activity contributes to vasodilatation. These substances signal the smooth muscle lining blood vessels to relax, leading to an increase in blood vessel diameter. This increase in diameter reduces vascular resistance, allowing more blood to flow to the active muscles that are working harder during exercise.

In contrast, vasoconstriction, which is the narrowing of blood vessels, would impede blood flow rather than enhance it. More nerve impulses to the muscle could increase muscle contraction but do not necessarily increase blood flow. Increased respiration supports oxygen uptake but does not directly lead to increased blood flow within the muscles themselves. Thus, the correct mechanism by which blood flow is increased during exercise is through vasodilatation.