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