- Mammals have many Mechanisms to Change Body Temperature
- Heat Loss
- SWEATING - more sweat is secreted from sweat glands when the body's too hot. The water in sweat evaporates from the surface of the skin and takes heat from the body. The skin is cooled
- HAIRS LIE FLAT- mammals have a layer of hair that provides insulation by trapping air (air is poor conductor of heat. When it's hot, erector pili muscles relax so the hairs lie flat. Less air is trapped, so the skin is less insulated and heat can be lost more easily.
- VASODILAT-ION - when it's hot, arterioles near the surface of the skin dilate ( this is called vasodilation). More blood flows through the capillaries in the surface layers of the dermis. This means more heat is lost from the skin by radiation and temperature is lowered.
- Heat Production
- SHIVERING - when it's cold, muscles contract in spasms. This makes the body shiver and more heat is produced from increased respiration.
- HORMONES - the body releases adrenaline and thyroxine. These increase metabolism and so more heat is produced
- Heat Conservation
- MUCH LESS SWEAT- less sweat is secreted from sweat glands when it's cold, reducing the amount of heat loss.
- HAIRS STAND UP - erector pili muscles contract when it's cold, which makes the hairs stand up. This traps more air and so prevents heat loss.
- VASOCONS-TRICTION - when it's cold, arterioles near the surface of the skin constrict (this is called vasoconstric-tion) so less blood flows through the capillaries in the surface layers of the dermis. This reduces heat loss.
- Heat Loss
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