Homeostasis

Your internal environment stays remarkably stable despite constant change outside. Blood temperature, glucose, water, and pH are all held within narrow limits. This maintenance of a steady internal state is called homeostasis, and it is essential because enzymes and cells function properly only within specific ranges.

Negative feedback: the core mechanism

Most homeostatic control relies on negative feedback. When a variable drifts away from its set point, the body detects the change and triggers a response that reverses it, returning the variable toward normal. The general loop has three components:

• Receptor — detects the change in the variable.
• Control center — usually the brain or an endocrine gland; compares the value to the set point.
• Effector — a muscle or gland that produces the cor