Question

Outline and diagram the effects of Vasopressin (ADH) on the nephron, and how it promotes water conservation in the kidneys. Be sure to EXPLAIN the cellular mechanisms of action.

Answer 1

osmoreceptors in the body are activated by changes ith blood volume,body fluid volume and ionic concentraion. an excessive loss of fluid from the body can activate these receptors which stimulate the hypothalamus to release anti diuretic hormone or vasopressin from theneurohypophysis.

Final concentration of urine is achieved by the action of ADH. Normally, the distal convoluted tubule and collecting duct of nephron are not permeable to water. But the presence of ADH makes them permeable, resulting in water reabsorption. Water reabsorption induced by ADH is called facultative reabsorption of water

Mechanism of action of ADH – Aquaporins
Antidiuretic hormone increases water reabsorption in distal convoluted tubules and collecting ducts bystimulating the water channels called aquaporins. ADH combines with vasopressin (V2) receptors in the tubular epithelial membrane and activates adenyl cyclase, to form cyclic AMP. This cyclic AMP activates the aquaporins, which increase the water reabsorption.
Aquaporins (AQP) are the membrane proteins, which function as water channels. Aquaporin­1, 2 and 3 are present in renal tubules. Aquaporin­2 forms the water channels in renal tubules.