What homeostasis isSpec 4.5.1
In short
Homeostasis is the regulation of the internal conditions of a cell or organism to maintain optimum conditions for function, in response to internal and external changes. It keeps conditions close to the optimum for enzyme action and all cell functions. In humans it controls blood glucose concentration, body temperature and water levels, using automatic nervous or chemical responses.
Cells in the body can only survive within narrow physical and chemical limits. They need a constant temperature and pH, and a constant supply of dissolved food and water. The body therefore has control systems that constantly monitor and adjust the composition of the blood and tissues.
- Homeostasis
- The regulation of the internal conditions of a cell or organism to maintain optimum conditions for function, in response to internal and external changes.
Homeostasis maintains optimal conditions for enzyme action and for all cell functions. If conditions drift too far from the optimum, enzymes work more slowly or stop working, and cells cannot carry out their reactions.
In the human body, homeostasis includes control of:
- blood glucose concentration
- body temperature
- water levels
These control systems are automatic. They may involve nervous responses or chemical responses (hormones).
Homeostasis does not keep conditions exactly the same all the time. It keeps them close to the optimum. Link your answer to enzymes working at their best.
Written and checked against the AQA GCSE Combined Science (8464) specification · Updated October 2026