What term describes the processes that increase or decrease the diameter of a blood vessel?

What term describes the processes that increase or decrease the diameter of a blood vessel?

• A. Conduction
• B. Vasodilation and Vasoconstriction
• C. Diffusion
• D. Peristalsis

Answer: (B)

The change in a blood vessel’s diameter is governed by the smooth muscle in its wall, which can relax or contract to widen or narrow the lumen. When the smooth muscle relaxes, the vessel diameter increases—this is vasodilation. When the smooth muscle contracts, the diameter decreases—this is vasoconstriction. These opposing actions together regulate blood flow and vascular resistance to meet the body's needs, with factors like autonomic nerve input, hormones, and endothelium-derived signals (for example, nitric oxide promoting dilation or endothelin promoting constriction) guiding the response. Other terms don’t describe this diameter-change process. Conduction refers to electrical signal propagation, diffusion is the spread of particles from high to low concentration, and peristalsis is the rhythmic propulsion seen in some ducts and the digestive tract.

The change in a blood vessel’s diameter is governed by the smooth muscle in its wall, which can relax or contract to widen or narrow the lumen. When the smooth muscle relaxes, the vessel diameter increases—this is vasodilation. When the smooth muscle contracts, the diameter decreases—this is vasoconstriction. These opposing actions together regulate blood flow and vascular resistance to meet the body's needs, with factors like autonomic nerve input, hormones, and endothelium-derived signals (for example, nitric oxide promoting dilation or endothelin promoting constriction) guiding the response.

Other terms don’t describe this diameter-change process. Conduction refers to electrical signal propagation, diffusion is the spread of particles from high to low concentration, and peristalsis is the rhythmic propulsion seen in some ducts and the digestive tract.