Keeping internal conditions steady

By UK GCSE Biology · independent study · myAudience

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Keeping internal conditions steady

Homeostasis regulates internal conditions within ranges suitable for cell function. Examples include blood glucose concentration, water balance and temperature. A receptor detects a change, a coordination centre processes information, and effectors produce a response.

Blood glucose, body temperature and water balance are regulated because cells function within suitable conditions. Homeostasis does not mean the body never changes: exercise, food intake and environmental changes create disturbances. A good explanation follows the disturbance, detection and corrective action rather than claiming that one organ maintains every internal variable unchanged.

The regulated value is the variable being controlled, not necessarily a single exact number. After a disturbance, receptors detect information about conditions; a coordination centre organizes signals, and effectors alter the variable. A response can fail to restore conditions if the disturbance is too large or the control system is impaired. Calling a response homeostatic therefore requires explaining which internal condition it helps regulate, not simply saying that the body reacted.

Worked example: Temperature rises above the usual regulated range. What kind of response would restore it?

Identify the upward disturbance

A corrective response should increase heat loss or reduce heat gain

Answer: A response opposing the rise supports homeostasis.

Check your understanding: Are receptors and effectors the same role?

Answer: No.

Why: Receptors detect change; effectors carry out a response.