Homeostasis and negative feedback

  • Created by: Katieh211
  • Created on: 12-03-14 14:25
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  • Homeostasis and negative feedback
    • Homeostasis
      • The maintenance of the internal environment in a constant state despite external changes
      • Many organisms have to keep a great deal of conditions constant inside the body. Such as:
        • Body temperature
        • Blood glucose concentration
        • Blood salt concentration
        • Water potential of the blood
        • Blood pressure
        • Carbon dioxide concentraion
    • Negative feedback
      • In order to maintain a constant internal environment a number of processes must occur.
        • Any change to the internal environment must be detected
          • The change must be signalled to other cells.
            • There must be a response that reverses the change
      • The reversal of a change in the internal environment to return to a steady state or optimum position
      • For negative feedback to work effectively there must be a complex arrangement of structures that are all coordinated through cell signalling.
        • Stimulus-Receptor- communication pathway (cell signalling)-effector-response
          • There are a number of structures required for this pathway to work
            • Sensory receptors
              • Temperature receptors or glucose concentration receptors.
              • They are internal and monitor conditions inside the body
            • A communication system
              • The nervous system or the hormonal system
              • Signals between cells
              • Transmits a message from the receptor cells to the effector cells
            • Effector cells
              • Liver cells or muscle cells
              • These bring about a response that reverses the change detected by the receptor cells.
    • Positive feedback
      • Less common than negative feedback
      • A process that increases any change detected by the receptors. It tends to be harmful and does not lead to homeostasis


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