Maintaining a constant internal environmentSpec 7.9
- Homeostasis
- Maintaining a constant internal environment in response to internal and external change.
Conditions inside the body change. Eating a meal changes blood glucose. Exercise raises body temperature. A hot or cold day changes the temperature outside. The body responds to keep the conditions inside constant.
| Condition | Example of a change |
|---|---|
| Blood glucose concentration | A meal raises it, exercise lowers it |
| Body temperature | Hot or cold surroundings, or exercise |
| Water content of the blood | Sweating, or drinking a lot |
This matters because enzymes and cells work best in a narrow range of conditions. If conditions drift too far, reactions in cells slow down or stop. Many of these controls use negative feedback.