BY4 - Homestasis

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  • BY4 - Homeostasis
    • Mechanisms by which a constant internal environment is achieved
      • Internal Environment - Made up of tissue fluids that bathe cells, supplying nutrients and removing waste
        • Maintaining these fluids at an optimum level protects the cells from changes in the external environment
          • Changes in temperature, pH and water potential still take place and fluctuate around a set point
    • All homeostatic processes include a control system
      • Detector
        • Coordinator
          • Effector
            • Carry out the corrective procedure to return the factor back to the set point
              • E.G. Collecting duct in the nephron in the kidneys
          • Communicates with one or more effectors
            • E.G Pituitary gland - releases ADH hormone
        • Detects any deviation from a set point
          • E.G. Osmo-receptors in the hypothalamus of the brain
      • Negative feedback
        • Once the correction is made the condition/ factor returns to the set point
          • Information is fed back to the detector and the co-ordinator switches off
    • Kidneys
      • Osmo-regulation
        • The control of water content and solute composition of body fluids
        • Homeostatic control of body water
      • Kidneys remove anything that causes an imbalance to the water potential
        • E.G. Urea
          • Formed from the break down of excess amino acids and nucleic acids
            • In the liver
            • Excess amino acids cannot be stored unlike fats and carbo-hydrates
              • Instead they are DEAMINATED (amine group is removed)
      • Nephron Features
        • Glomerulus
          • Ultrafiltration
            • Bowman's Capsule
        • Bowman's Capsule
        • Proximal Convoluted Tubule
          • Selective Reabsorption
        • Loop of Henle
          • Controls solute concentration and water potential
        • Distal Convoluted Tubule
        • Collecting Duct
          • Osmo-regulation


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