Describe control of ADH on urine output.

Antidiuretic hormone (ADH) or vasopressin hormone : Urine output is inversely proportional to ADH. It is secreted by hypothalamus and released through posterior lobe of pituitary gland.

If there is excess of water in body then ADH is secreted in less amount so that urine output is increased and if there is less amount of water in the body then ADH is secreted more, because osmoreceptors in hypothalamus detect an increase in osmolarity of blood above a set point of 300 mosml–1, so that urine output is decreased. In this condition osmorecptor cells promote thirst. Drinking reduces osmolarity of blood. Those substances which increase urine output are called diuretics e.g. alcohol, tea, coffee and all type of non-alcoholic drinks etc. Control of ADH is a negative feed back circuit.