Reduced heat loss response

Physiological mechanisms to reduce heat loss include:

• reduced sweating: however, minimal effect because sweating does not tend to occur at temperatures lower than 36 degrees centigrade. Insensible losses are still present and cannot be regulated.
• piloerection: the sympathetic nervous system stimulates the arrectores pilorum smooth muscle in skin to raise hairs up from the skin surface. This 'traps' a layer of insulating air in animals with fur, so reducing heat loss by conduction and radiation. The response is present in Man - characterised by 'goose flesh' - but is functionally unimportant due to the sparsity of hairs.
• vasoconstriction: the posterior hypothalamus increases sympathetic vasoconstriction of arteriolar and pre-capillary smooth muscle. This results in less blood travelling through the superficial arcades of the skin, losing heat energy in transit. Also, vasoconstriction aids the counter current heat exchange mechanism between arteries and their associated venae comitantes.