2.77 Homeostasis

2.77 understand that homeostasis is the maintenance of constant internal environment and that body water content and body temperature are both examples of homeostasis

Homeo~ = ‘same’/’constant’
~stasis = ‘conditions’
Homoeothermic = constant temperature

Mammals maintain a constant body temperature no matter what the environmental temperature; these are homoeothermic organisms and carry out Thermoregulation.
Mammals must contain this constant body temperature in order to maintain optimum temperatures for enzyme catalysed reactions.

Thermoregulation:

A negative feedback loop is used to regulate body temperature in the human body about a constant condition. For human body temp, this constant condition (the co-ordinator) is roughly 37°C.

In thermoregulation the receptor is the Hypothalamus, a region of the brain that responds to a stimulus: the temperature of Blood. The hypothalamus compares the body temperature of blood to the theoretical level (37°C). If the body temperature needs to be increased or decreased effectors such as the skin are used to create a responsive increase or decrease in body temperature. This temperature feeds back to the hypothalamus to produce a new output.

Using Skin to Regulate body temperature:

There are several important features of the skin used to regulate body temperature: these include sweat glands, hair, and blood vessels.

On a hot day when body temperature needs to be lowered blood flow to the surface of the skin increases through dilated blood vessels and the body is cooled through the evaporation of sweat and radiation of heat from the blood.

On a colder day less blood is pumped towards the surface of the skin as the blood vessels constrict allowing less heat to radiate from the body. The hairs also stand upright in order to trap air as an insulation layer.