When the body becomes too hot, the arterioles supplying the skin capillaries
Correct answer: C. dilate, so more blood flows near the surface and more heat is lost
- A. constrict, so less blood reaches the surface
- B. are unaffected, since only sweating matters
- C. dilate, so more blood flows near the surface and more heat is lost
- D. carry blood away from the skin into deeper shunt vessels
Explanation
Vasodilation of the arterioles lets more warm blood flow through the surface capillaries, so heat is lost by radiation and conduction and the skin looks flushed. In the cold these arterioles constrict and blood is diverted through deeper shunt vessels, keeping the skin pale and conserving heat. The capillaries themselves have no muscle, so they cannot dilate or constrict on their own.
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About Thermoregulation
Thermoregulation maintains body temperature through negative feedback controlled mainly by the hypothalamus. It covers vasodilation and vasoconstriction, sweating, shivering, changes in metabolic heat production and behavioural responses, while distinguishing heat loss by radiation, conduction, convection and evaporation from temperature regulation itself.
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