Rise in water potential response

• A fall in solute concentration causes the water potential of the blood to rise.
• When the blood water potential rises, firstly the osmoreceptors in the hypothalamus will detect this. This is because when the water potential is too high, water moves into the osmoreceptor cells, causing them to swell.
• When the osmoreceptor cells swell, this triggers an increase in the frequency of nerve impulses to the pituitary gland in order to reduce the release of ADH.
• Since there is less ADH being released, the collecting ducts of the kidneys will become less permeable to water and urea, meaning that less water is reabsorbed into the kidneys and more dilute urine is produced and released. This causes the blood water potential to fall.
• Once the water potential of the blood has been returned to normal, the osmoreceptors in the hypothalamus cause the pituitary to raise/lower its ADH release back to normal levels. This forms the negative feedback loop.