Cambridge O Level Biology · Syllabus 5090 · Coordination and Control
Vasodilation
What is Vasodilation?
The widening of the arterioles that supply the capillary networks near the skin surface. More warm blood then flows close to the surface, so more thermal energy is transferred to the surroundings and body temperature falls towards the set point. Capillaries themselves cannot widen, because their walls are one cell thick and contain no muscle.
This definition is part of the Coordination and Control chapter in Cambridge O Level Biology.
Common mistakes with Vasodilation
- Two marks. "You sweat and your blood vessels get bigger so you cool down." Sweating is there and vasodilation is roughly there, but nothing is linked: it does not say the sweat must evaporate, it does not say which vessels widen, and "cool down" is a restatement of the question rather than a mechanism.
Questions students ask about Vasodilation
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.