Osmoregulation

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  • Created by: Steff06
  • Created on: 03-03-16 19:57
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  • Osmoregulation
    • = The control of WATER and SALT levels in the body.
    • Water is GAINED from food, drink and metabolism. Water is LOST in urine, sweat, water vapour in exhaled air, faeces.
    • When conserving LESS water, walls of the COLLECTING DUCT are LESS PERMEABLE. So LESS water is reabsorbed and MORE urine will be produced. Opposite for conserving MORE water.
    • WALLS of collecting duct respond to level of ANTIDIURETIC HORMONE (ADH) in the BLOOD.
    • ADH BINDS to RECEPTORS in cells in wall and cause ENZYME-controlled reactions.
    • Causes insertions of vesicles containing AQUAPORINS into cell surface membrane. Makes walls MORE PERMEABLE to WATER.
      • LESS ADH = cell surface membrane FOLDS inwards to create vesicles that remove aquaporins from membrane.
    • Adjusting concentration of ADH in blood:
      • 1. WATER POTENTIAL measured by OSMORECEPTORS in HYPOTHALAMUS.
        • 2. When water potential = LOW, OSMORECEPTOR cells LOSE water by OSMOSIS.
          • 3. NEUROSECRETORY cells release ADH by sending ACTION POTENTIALS down their AXONS.
            • 4. ADH enters BLOOD CAPILLARIES and acts on cells of COLLECTING DUCTS.
              • 5. Once water potential of blood RISES, LESS ADH is released.
                • 6. ADH is slowly broken down and collecting ducts will receive less stimulation.

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