Cambridge O Level Biology · Syllabus 5090 · Coordination and Control
Vasoconstriction
What is Vasoconstriction?
The narrowing of the arterioles that supply the capillary networks near the skin surface. Less blood then flows close to the surface, so less thermal energy is transferred to the surroundings and body temperature rises towards the set point. Blood flow to the skin is reduced, not stopped.
This definition is part of the Coordination and Control chapter in Cambridge O Level Biology.
Questions students ask about Vasoconstriction
What is the difference between vasodilation and vasoconstriction?
Vasodilation is the widening of the arterioles supplying the capillaries near the skin surface, increasing blood flow there and increasing heat loss. Vasoconstriction is the narrowing of those same arterioles, reducing blood flow and reducing heat loss. Capillaries themselves cannot change diameter, because their walls are one cell thick and contain no muscle.