Feedback control of ADH secretion

Feedback control of ADH secretion, one of the negative feedback loops from kidneys to the brain that helps adjust the volume of extracellular fluid.

1 Osmoreceptors in the brain detect an increased Na+ concentration and alertthe hypothalamus.
2 Action potentials travel from cell bod-ies in the hypothalamus to axon terminals in the posterior pituitary. These terminals release ADH, which enters the blood.  
3 ADH binds to cells that make up the walls of distal tubules and collecting tubules. Binding of ADH makes these cells more permeable to water.
4 When the Na+ concentration returns to within its normal range, osmorecep-tors stop signaling, and ADH secretion ceases.
5 More water is reabsorbed across the distal tubule and collecting tubule. As blood volume rises, Na+ concentration declines.