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Homeostasis is the maintenance of a constant internal environment.

The nervous system and hormones are responsible for this.

Example: the concentration of carbon dioxide in the blood being carefully controlled. [1]

Blood sugar level

This is controlled to provide cells with a constant supply of glucose for respiration.

It is controlled by the release and storage of glucose, which is in turn controlled by insulin. [2]

Negative feedback

Homeostatic control is achieved using negative feedback mechanisms:

- if the level of something rises, control systems reduce it again

- if the level of something falls, control systems raise it again [3]

Body temperature

This is controlled to maintain the temperature at which the body’s enzymes work best, which is usually 37°C. [4]

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 [5]

Bitesize - The circulatory system








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