when body temperature increases what happens to blood vessels
As a consequence, the blood pressure usually increases by 20 to 60 mm Hg, which helps sustain the increased blood flow through skeletal muscle blood vessels. In response to sympathetic stimulation, some decrease in the blood flow through the skin can occur at the beginning of exercise. However, as the body temperature increases in response to the increased muscular activity, temperature receptors in the hypothalamus are stimulated. As a result, action potentials in sympathetic nerve fibers causing vasoconstriction decrease, resulting in vasodilation of blood vessels in the skin.
Blood and temperature control - Higher. When we are too hot, blood vessels supplying blood to the skin can swell or dilate (vasodilation). This allows more warm blood to flow near the surface of the skin, where the heat can be lost to the air. This is why some people's skin looks redder when they feel too hot. When we are too cold the blood vessels supplying warm blood to the skin become narrow or constrict (vasoconstriction). This reduces the flow of warm blood near the surface of the skin, and reduces heat loss. This is why some people's skin looks paler when they feel too cold.