Osmoregulation

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  • OSMO- REGULATION
    • the control of water levels and salt levels in the body
    • to prevent problems with osmosis
      • RBC's
        • haemolysed
    • ADH
      • antidiuretic hormone
      • released by posterior pituitary glands
      • acts on collecting duct
      • first messenger: binds to receptors
        • adenyl cylase: ATP-->cAMP
          • enzymecontrolled reactions
          • aquaporins inserted in cell membrane
            • more channels for water to flow through
      • broken down
        • half life of 20 mins
        • otherwise continually acts on collecting ducts
        • membranes infold to create new vesicles (endocytosis)
    • DETECTION
      • osmoreceptors
        • shrink when low water potential
        • stimulate neurosecretory cells
        • found in hypothalamus
      • neurosecretory cells
        • release AHD inot the blood
        • action potential down axon
        • manufacture AHD in cell body
        • differs from other nerve cells
          • hormones made in cell body
          • hormone into blood rather than other nerve cell
      • posterior pituitary gloands
        • where AHD is stored
        • released when action potential passes down the axon
    • decrease in water potential
      • MORE ADH
      • exocytosis of aqaua porins
      • MORE permeable
      • LESS urine produced
      • MORE reabsorped
    • increase in water potenital
      • endocytosis of aquaporins
      • LESS ADH
      • LESS permeable
      • LESS reabsorped
      • MORE urine produced
    • example of negative feedback control
    • DRUGS + HORMONES
      • Antiduretics
        • LESS water lost
        • MORE permeable membrane
        • MORE aquaporins
        • treatments for
          • diabetes
          • bed wetting
      • Diuretics
        • LESS aquaporins
        • LESS permeable membrane
        • MORE water lost
        • treatments for
          • coffee
          • relieve water retention
          • reduce swelling
          • reduce high blood pressure
    • WATER
      • LOST
        • urine
        • sweat
        • water vapour in exhaled air
        • faeces

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