Explain how anti-diuretic hormone (ADH) is released and acts on cells in the collecting duct wall?

Osmoreceptors in the hypothalamus detect a change in the water potential of blood, this stimulates neurosecretory cells to make and release ADH. ADH travels down the axon to the terminal bulb in the posterior pituitary gland . It is then secreted into the capillaries and blood stream where it acts on the collecting duct wall of nephrons.

ADH is detected by cell surface receptors on the collecting duct wall causing vesicles containing aquaporins (water permeable channels) to fuse and be inserted into the cell surface membrane. This allows for the uptake of water into the blood stream