What is vasodilation?

What is vasodilation?

• A. The widening of blood vessels, allowing greater blood flow to the muscles.
• B. Narrowing of blood vessels that reduces blood flow.
• C. An increase in blood viscosity.
• D. A decrease in heart rate.

Answer: (A)

Vasodilation is the widening of blood vessels, especially the small arteries and arterioles. When the vessels relax and their diameter increases, the resistance to blood flow drops, so more blood can reach the tissues with the same pressure difference. In exercising muscles, this increased flow delivers more oxygen and nutrients and helps remove heat and metabolic wastes, supporting the higher energy demand. Local signals from the working muscles—such as nitric oxide, carbon dioxide, lactic acid, and adenosine—promote this relaxation of the vessel walls, a process sometimes called functional dilation. The other ideas describe either the opposite process (vasoconstriction, which narrows vessels), or other unrelated factors (blood viscosity or heart rate changes) that don’t define vasodilation.

Vasodilation is the widening of blood vessels, especially the small arteries and arterioles. When the vessels relax and their diameter increases, the resistance to blood flow drops, so more blood can reach the tissues with the same pressure difference. In exercising muscles, this increased flow delivers more oxygen and nutrients and helps remove heat and metabolic wastes, supporting the higher energy demand. Local signals from the working muscles—such as nitric oxide, carbon dioxide, lactic acid, and adenosine—promote this relaxation of the vessel walls, a process sometimes called functional dilation. The other ideas describe either the opposite process (vasoconstriction, which narrows vessels), or other unrelated factors (blood viscosity or heart rate changes) that don’t define vasodilation.