OSMOREGULATION THEORY

1. If the water potential of the blood plasma decreases e.g. dehydration, the osmoreceptors in the hypothalamus are stimulated. 2.. This causes impulses to be sent to the posterior pituitary gland and the hormone ADH is released into the blood. (ADH is transported to the kidneys)  3.ADH binds to receptor proteins in the epithelial cell membrane that line the distal convoluted tubule and the collecting duct. 4. The binding of ADH causes aquaporins (water channel proteins) to be inserted into the membrane. This increases the DCT and collecting duct’s permeability to water.  5. Increased water moves out of the DCT, through the aquaporins and into the capillaries (by osmosis). This raises the blood water potential. 6.As a result a decreased volume of urine is produced. 7.7. As water is reabsorbed the water potential of the blood returns to normal (negative feedback).