In vasodilation, the blood vessels near the surface of the skin become wider (dilate) to allow more blood to flow near to the skin surface and therefore lose more heat and the body will cool down. In vasoconstriction, the blood vessels near the surface of the skin narrow (constrict) to restrict the volume of blood flow near the skin, so less blood transfers heat and the body loses less heat.
What are arteirioles and what do they do in different temperature changes?? Thx
Exactly what I said above. I assume you're GCSE in which case you don't need to know about arterioles, just the action of blood vessels. But for extra knowledge, arterioles are smaller arteries that join up ateries and capillaries.