Question

Describe the negative feedback loop that controls the secretion of ADH by the posterior pituitary?

Answer 1

ADH is stored in the nerve endings of posterior pituitary gland in the form of large secretory granules.ADH secretion is under the control of electrical impulses from the supraoptic nuclei present within hypothalamus.With the impulses travelling down the nerve endings, ADH is released.The secretion of ADH is under a negative feed back loop of osmoregulation and baroregulation.Osmoreceptors are present in hypothalamus near to the ADH secreting cells that respond to changes in concentration of extracellular fluid (ECF).A concentrated ECF stimulates release of ADH while a diluted ECF inhibits ADH secretion.Baraceptors respond to changes in pressure and this affects ADH secretion.A decreased blood volume and pressure activates the baroreceptors that send impulses to supraoptic nerve in hypothalamus and ADH is secreted but an increased blood volume and pressure inhibits ADH secretion.