How does the body respond to a decrease or increase in core body temperature?

If the temperature decreases:The blood vessels supplying the skin constrict (vasoconstriction) resulting in less blood flow to the skin surface and hence less energy (by heat) is lost. Hairs stand on end to trap warm air by creating an insulating layer, shivering by muscle contraction generates heat by respiration and sweating stops.If the temperature increases:The blood vessels supplying the skin dilate (vasodilation) resulting in more blood flow to the skin surface and hence more energy (by heat) is lost. Hairs lay flat, muscles relax and sweat is produced from sweat glands. Sweat is a liquid which retains heat and hence when it evaporates from the surface of the skin more energy is lost.Homeostasis is the maintenance of a constant internal environment, this is needed for enzyme actions which catalyse metabolic reactions and all cell functions. In particular, temperature is important to control because if it is too hot, enzymes in the body will denature and become inactive. On the other hand, if it is too cold, the enzymes will too become ineffective as their function will slow down due to a lower kinetic energy of particles.