physiology
Last reviewed 01/2018
There are many stimuli to ADH secretion. The most relevant physiologically is change in blood osmolalilty. For example, if extracellular fluid (ECF) volume changes without a corresponding change in the amounts of solutes, then the osmolality of the ECF will change. The osmolality of the ECF is normally 280-295 mOsmol/kg. At around 287 mOsm/kg, the hypothalamic nuclei controlling water metabolism signal to the local ADH-secreting supraoptic and paraventricular nuclei.
ADH, which has descended within the axons - the hypothalamic-hypophyseal tract - of the neurons in this area to the posterior pituitary, is then stored. The signal for release is nerve impulses down the same neurons.
ADH is released with its carrier protein into:
- closely approximed capillaries leading to:
- the systemic circulation
- the anterior pituitary
- CSF