Osmoregulation

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  • Created by: portia
  • Created on: 29-04-17 09:55

Control of water content 

Osmoreceptors, the hypothalamus and ADH

  • osmoregulation is the control of the water potential of body fluids
  • it involes the hypothalamus, prosterior pituitary gland and the kidneys
  • water potential of blood is constantly monitored by specialised sensory neurones in the hypothalamus known as osmoreceptors
  • if these cells detect a decrease in water potential of blood below set point, nerve impulses are sent along the neurones to where they terminate in the prosterior pituitary gland
  • these impulses stimulate the release of antidiuretic hormone (ADH), a peptide hormone
  • ADH molecules enter blood capillaries and are carried all over the body
  • the effect of ADH is to reduce loss of water in urine by making kidneys reabsorb as much water as possible
  • diuresis is the production of dilute urine
  • Antidiuretic hormone gets its name because it stops dilute urine being produced, by stimulating the reabsorption of water

How ADH affects the kidneys

  • water is absorbed by osmosis from fluid in the collecting duct
  • the cells of the collecting duct are the target cells for ADH
  • this hormone acts on the cell surface membranes of the collecting ducts, making them more permeable to water than usual
  • this change in permeability is brought about by increasing the number of the water-permeable channels known as aquaporins in cell surface membrane of collecting duct cells
  • ADH molecules…

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