Homeostasis

It is important that the body’s internal environment is controlled. For example, the amount of carbon dioxide in the bloodstream is carefully controlled.

Maintaining a constant internal environment is called homeostasis. The nervous system and hormones are responsible for this. Here are some of the other internal conditions that are controlled:

Blood sugar level

This is controlled to provide cells with a constant supply of energy. The blood sugar level is controlled by the release and storage of glucose, which is in turn controlled by a hormone called insulin.

Body temperature

This is controlled to maintain the temperature at which enzymes work best, which is 37°C. Body temperature is controlled by:

• controlling blood flow to the skin
• sweating
• shivering

The body’s water content

This is controlled to protect cells by stopping too much water from entering or leaving them. Water content is controlled by water loss from:

• the lungs when we exhale
• the skin by sweating
• the body, in urine produced by the kidneys

Feedback mechanisms - higher

Homeostasis is achieved by negative feedback mechanisms. The animation shows how this works when controlling the body’s water content.