Explain what is meant by 'homeostasis' and give an example of this process in the human body.

Homeostasis is the process of maintaining a constant internal environment in the body.

An example of this is maintaining the temperature of the body. Human body temperature must be maintained at 37ºC as this is the optimum temperature for human enzymes to work. High temperatures can cause dehydration and eventually death and low temperatures can cause hypothermia and lead to death therefore body temperature must be maintained constant.

The temperature of the body is regulated by the brain. The part of the brain that is involved is called the hypothalamus. It can sense the temperature of the body and then send nerve impulses down to the skin and muscles to increase or decrease heat loss.

There are a few mechanisms that the hypothalamus uses to regulate body temperature:

Firstly, if your body is too hot, sweat glands in the skin secrete sweat onto the surface of the skin. The sweat then evaporates to cause heat loss.

Secondly, the hairs on the body can be moved upright or flat by small muscles in the skin. When upright, the hairs trap warm air to warm the body up and when flat they increase heat loss.

Thirdly, there are blood vessels inside the skin which can swell (dilate) to allow more warm blood to flow nearer the skin surface. This way, heat can be transferred through the skin and away from the body to increase heat loss. Also, the blood vessels can become smaller (constrict) so that less heat is lost if the body is cold.

Lastly, your muscles also receive messages from the brain to tell them to move when cold. This causes shivering which warms the body up.

Through these mechanisms, the body temperature is kept constant, an example of homeostasis.