The conditions inside our body must be carefully controlled if it is to function effectively. Homeostasis is the maintenance of a constant internal environment in the body. The nervous system and the endocrine system - which produces hormones - are involved in homeostasis.
The body control systems have three basic parts:
Body temperature is one of the factors that is controlled during homeostasis. The human body maintains the temperature at which enzymes work best, which is around 37°C. This process is controlled by the thermoregulatory centre, which is contained in the hypothalamus in the brain, and it contains receptors sensitive to the temperature of the blood. The skin also has temperature receptors and sends nervous impulses back to the thermoregulatory centre.
When we get too cold:
When we get too hot:
The hairs on the skin also help to control body temperature. The hairs lie flat when we are warm, and rise when we are cold.
If we are too cold, nerve impulses are sent to the hair erector muscles which contract. This raises the skin hairs and traps a layer of insulating air next to the skin.
The control of body temperature is an example of a negative feedback mechanism. It regulates the amount of:
The amount of blood flowing through the skin capillaries is altered by vasoconstriction and vasodilation.
|Too cold||Too hot|
|Arterioles||Get narrower||Get wider|
|Blood flow in skin capillaries||Decreases||Increases|
|Heat loss from skin||Decreases||Increases|
These diagrams show the processes that take place when vasoconstriction and vasodilation occur.
Generally, when the body temperature is too low, a variety of processes happen - vasoconstriction, sweating stops and shivering starts.
When the temperature is too high, different processes happen - vasodilation and sweat production, which both transfer energy from skin to the environment, resulting in a cooling effect.