Maintaining the internal environment
Homeostasis is the maintenance of a stable internal environment within restricted limits.
Physiological control systems keep internal conditions within a narrow range so that cells can continue to function effectively. Conditions may change, but control systems respond before they move too far from suitable levels.
Examples of internal conditions regulated in mammals include:
- core body temperature
- blood pH
- blood glucose concentration
- water potential of the blood
Parts of a physiological control system
Receptor
A receptor detects a stimulus: a change in the internal or external environment.
Coordinator
Information is passed to a coordination system. Coordination may involve the nervous system, using nerve impulses, or the endocrine system, using hormones carried in the blood.
Effector
The coordinator signals an effector, which produces a response that changes the internal condition.
Some homeostatic responses involve the nervous and endocrine systems working together within the same control pathway.