exercies,fever, or an increase in environmental temperture tend to raise body temperature.
homeostasis requires the loss of excess heat. blood vessels (arterioles) in the dermis dilate and enable more blood to flow through the skin, thus transferring heat from deeper tissues to the skin where the heat is lost by radiation (infrared energy), convection (air movement), or conduction (direct contact with an object). sweat that spreads over the surface of the skin and evaporates also carries away heat and reduces body temperature.
If body temperature begins to drop below normal, heat can be conserved by constriction of dermal blood vessels, which reduces blood flow to the skin. thus, less heat is transferred from deeper structures to the skin, snd heat loss is reduced. with smaller amounts of warm blood flowing through the skin, however, the skin temperature decreases. If the skin temperature drops below 15 (59), blood vessels dilate.