First 122 words of the document:
Biology Unit 5
Topic 7: Run for your life
15. Explain the principle of negative feedback in
maintaining systems within narrow limits.
Negative feedback systems
Homeostasis is the maintenance of a stable internal environment, within a narrow limit, of the
optimum conditions needed by cells so they can function properly. A homeostatic system therefore
Receptors to detect the change away from the norm value (stimulus)
A control mechanism that can respond to the information. The control mechanism uses the
nervous system or hormones to switch effectors on or off
Effectors to bring about the response (usually to counteract the effect of the initial change).
Text Book: p.154