1.12 Homeostasis and negative feed back

  • Created by: JTY3
  • Created on: 16-03-16 21:17
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  • Homeostasis and negative feedback
    • Homeostasis
      • Keeping the internal environment constant even though the external environment changes.
      • Several conditions must be kept at a constant inside the body
        • Body temperature
        • blood glucose concerntration
        • blood salt concerntration
        • water potential of the blood
        • blood pressure
        • CO2 concerntration
    • Negative feedback
      • The reverse of a change in the internal environment to return to a steady state or optimum position
      • Several structures which have a complex arrangement make up the pathway of communication
        • Sensory receptors like glucose concentration  receptors
        • A communication system like the nervous system or the hormonal system
        • Effector cells like liver or muscle cells
    • Positive feedback
      • The increase of the original change that often leads the destablisation of the system which causes harm
        • Example: when the body gets too cold enzymes become less active slowing down exergonic reactions that release heat. this slowing continues as the body gets colder
      • An example of positive feedback being beneficial is at the end or pregnancy. as the cervix begins to stretch the change is signalled to the arterior pituritary gland which is stimulted to secrete the hormone oxytocin. Oxytocin increases uterine contractions which lead to further stretching of the cervix.


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