Key Definitions

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.

Internal environment: The conditions inside the body (temperature, blood glucose, water balance, pH) that must be kept within a narrow range for cells and enzymes to function properly.

Receptor: A cell or organ that detects a change (stimulus) in the internal or external environment and sends a signal to the coordination centre.

Coordination centre: The component of a control system (e.g. brain, spinal cord, pancreas) that receives and processes information from receptors and sends instructions to effectors.

Effector: A muscle or gland that responds to instructions from the coordination centre, producing a response that corrects the detected change.

Negative feedback: A control mechanism in which a change from the normal level triggers a response that opposes and reverses the original change, restoring conditions to normal.

Stimulus: A detectable change in the internal or external environment that triggers a response from a receptor.

Optimum conditions: The specific temperature and pH at which an enzyme (or cellular process) works at its maximum efficiency.