What happens to a blood vessel's diameter when the smooth muscle relaxes?

Prepare for the Anatomy and Physiology II Exam with comprehensive questions and detailed explanations. Gain confidence with our tailored quizzes and maximize your exam performance!

Multiple Choice

What happens to a blood vessel's diameter when the smooth muscle relaxes?

When smooth muscle in a vessel wall relaxes, the muscle fibers loosen their grip on the vessel. The result is a drop in the contractile tone of the wall, allowing the lumen to widen. This widening is vasodilation, which increases blood flow to the tissues served by that vessel. On a molecular level, relaxation involves a decrease in intracellular calcium and a shift toward the inactive state of the contractile machinery, so the vessel can expand rather than constrict. Vasodilation is the natural response when tissues need more blood supply, and it contrasts with vasoconstriction, where smooth muscle contracts to narrow the lumen. Torsion refers to twisting and does not describe a change in diameter, so it’s not applicable here.

When smooth muscle in a vessel wall relaxes, the muscle fibers loosen their grip on the vessel. The result is a drop in the contractile tone of the wall, allowing the lumen to widen. This widening is vasodilation, which increases blood flow to the tissues served by that vessel. On a molecular level, relaxation involves a decrease in intracellular calcium and a shift toward the inactive state of the contractile machinery, so the vessel can expand rather than constrict.

Vasodilation is the natural response when tissues need more blood supply, and it contrasts with vasoconstriction, where smooth muscle contracts to narrow the lumen. Torsion refers to twisting and does not describe a change in diameter, so it’s not applicable here.

More practice questions