14.1.2

Negative Feedback

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Negative Feedback

Negative feedback is the mechanism that restores systems to the original level. The steps involved in these mechanisms are:

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1) Detect change

  • Change in the internal environment (stimulus) is detected by receptors.
  • Receptors (e.g. thermoreceptors) are stimulated when the level is too high or too low (e.g. temperature).
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2) Counteract change

  • Receptors send a signal to the effectors through coordination systems (nervous system or endocrine system).
  • The effectors counteract the change (e.g by restoring body temperature to 37°C).
  • Negative feedback can only maintain the internal environment within a specific range. If a change is too dramatic, negative feedback may not be able to prevent it.

Multiple Negative Feedback Mechanisms

Multiple negative feedback mechanisms provide a greater degree of control of the internal environment.

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More control

  • Multiple feedback mechanisms provide more control because the body can respond to multiple changes away from the optimum.
    • E.g. Body temperature can be reduced or increased by multiple mechanisms.
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Faster response

  • Multiple feedback mechanisms also provide a faster response because the body can respond in more ways to a change away from the optimum.
    • E.g. If body temperature decreases, negative feedback can increase body temperature by both shivering and vasoconstriction.

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1Cell Structure

2Biological Molecules

3Enzymes

4Cell Membranes & Transport

5The Mitotic Cell Cycle

6Nucleic Acids & Protein Synthesis

7Transport in Plants

8Transport in Mammals

9Gas Exchange

10Infectious Diseases

11Immunity

12Energy & Respiration (A2 Only)

13Photosynthesis (A2 Only)

14Homeostasis (A2 Only)

15Control & Coordination (A2 Only)

16Inherited Change (A2 Only)

17Selection & Evolution (A2 Only)

18Classification & Conservation (A2 Only)

19Genetic Technology (A2 Only)

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