Homeostasis

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  • Created by: Liv Scott
  • Created on: 06-03-15 10:18
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  • Homeostasis
    • Negative feedback
      • Blood glucose regulation
        • Islets of Langerhans
          • Drop in blood glucose conc.
            • Alpha cells secrete glucagon
              • Inhibit insulin secretion
              • Glycogenolysis - converts glycogen to glucose
              • More fatty acids used in respiration
              • Gluconeogenesis- conversation of amino acids & fats to glucose
          • Rise in blood glucose conc.
            • Beta cells secrete insulin
              • Inhibits glucagon production
              • Binds to receptors on hepatocytes
                • Activates adenyl cyclase
                  • Converts ATP to cAMP
                    • More glucose channels in the cell surface membrane
                      • More glucose enters cells
                      • Glycogenesis- glucose converted to glycogen
      • Brings about a reversal of a change back to the norm
    • Communication system
      • Hormonal
        • Slow response, long term
      • Neural
        • Quickly, through neurons
    • Thermoregulation
      • Endotherms
        • Use internal sources of heat to maintain body temp within a narrow range
          • Advantages
            • Constant internal temp, regardless of external temp
            • Activity possible in cold weather
            • Can live in cold climates
          • Disadvantages
            • More energy used up producing heat
            • More food needed
            • Less energy from food can be used for growth
          • Adaptations
            • Sweat
            • Alter breathing pattern
            • Alter body shape
            • Alter body shape
            • Move into/away from sun
            • Hair (lies flat or erect)
      • Ectotherms
        • Relies on external sources of heat to regulate body temp
          • Advantages
            • Constant internal temp. independent of external temp.
            • Activity possible in cold conditions e.g. winter
            • Can live in cold climates
          • Disadvantages
            • More energy used in producing heat energy
            • More food needed to make heat energy
            • Less of the energy from food used for growth
          • Adaptions
            • Move into/out of the sun
            • Change breathing movements
            • Alter body shape
    • Cell signalling
      • Cells need to communicate with each other
    • Positive feedback
      • Response is to increase the original change
        • E.g. hypothermia & labour contractions
    • The maintance of the internal environment in a stable state

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