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| Description: 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. Picture Stats: Views: 89 Filesize: 181.95kB Height: 688 Width: 1500 Source: https://biology-forums.com/index.php?action=gallery;sa=view;id=47434 |