--- title: "Osmoregulation and the Action of ADH" description: "Osmoregulation keeps blood water potential near its usual range. ADH changes water permeability in collecting duct cells, adjusting water reabsorption and the volume and concentration of urine." canonical: https://lightmysky.com/learn/science/osmoregulation-and-the-action-of-adh-mt_Rz_MmL-Pa- source: https://lightmysky.com/learn/science/osmoregulation-and-the-action-of-adh-mt_Rz_MmL-Pa-.md retrieved: 2026-11-12 --- > **Agent view.** This is the Markdown twin of the page, for tools and assistants. > When to use this site, and the call that answers each job: https://lightmysky.com/agent-instructions.md > API description (OpenAPI 3.1): https://lightmysky.com/openapi.json · Authentication: https://lightmysky.com/auth.md > Pricing: https://lightmysky.com/pricing.md · Catalog: https://lightmysky.com/llms.txt · Full catalog: https://lightmysky.com/llms-full.txt > Every machine-readable file on this domain: https://lightmysky.com/.well-known/ai-catalog.json > Ask for Markdown with `Accept: text/markdown`, a `.md` address, or `?mode=agent`. # Osmoregulation and the Action of ADH Osmoregulation keeps blood water potential near its usual range. ADH changes water permeability in collecting duct cells, adjusting water reabsorption and the volume and concentration of urine. Subject: Science · Area: The Human Body · Ages 17 to 18 Page: https://lightmysky.com/learn/science/osmoregulation-and-the-action-of-adh-mt_Rz_MmL-Pa- ## Ready when they can - Traces the loop from a fall in blood water potential through to a change in urine volume. - Explains how ADH increases collecting duct water permeability and water reabsorption. - Predicts what happens to urine concentration after a large drink of water. ## Lesson: How ADH tunes your urine Osmoregulation keeps blood water potential near its usual range. Water loss in sweat, or salt gain without enough water, can lower it. Osmoreceptors in the hypothalamus detect the fall. ADH means antidiuretic hormone: anti means against, and a diuretic increases urine volume. ADH reduces water loss in urine. It is made in the hypothalamus and released into the blood from the posterior pituitary. ADH travels in the blood to collecting duct cells. It increases aquaporin water channels in the membranes facing the fluid inside the duct. This makes the duct wall more permeable to water. In the kidney medulla, water can leave the duct by osmosis into tissue fluid with a lower water potential, then return to blood. This increases reabsorption of filtered water; it is different from forming filtrate by pressure at the glomerulus. *(drawing: Follow blood water potential through the response. Its recovery reduces the stimulus for ADH release.)* With healthy kidneys, more ADH increases water reabsorption and leaves a smaller volume of more concentrated urine. Returning water raises blood water potential towards its usual range. As the fall is corrected, the stimulus for ADH release decreases. This is negative feedback: the response opposes the change that started it. Urine colour can change for other reasons, so colour alone does not tell you the ADH level. **Example.** After a large drink has been absorbed, blood water potential may rise. Less ADH is then released, and fewer aquaporin channels remain in the tubule-facing membranes. The collecting duct becomes less permeable to water. Less water is reabsorbed, so a larger volume of dilute urine forms. This prediction assumes healthy kidneys. Dehydration means too little body water; diuresis means increased urine production. **Recap.** ADH increases collecting duct water permeability. More water returns to blood by osmosis, leaving a smaller volume of more concentrated urine. *Original lesson, questions and flashcards written for this dataset. Anatomy and Physiology and Khan Academy renal physiology were consulted for facts and teaching structure.* ## Practice 8 questions on this page, each with its working shown. ## Needs first - [Hormones and Negative Feedback](https://lightmysky.com/learn/science/hormones-and-negative-feedback-mt_OBa6BHmW29) - [Ultrafiltration and Selective Reabsorption in the Nephron](https://lightmysky.com/learn/science/ultrafiltration-and-selective-reabsorption-in-the-nephron-mt_vSKfoJN6zh) ## Opens up - [Transamination, Ammonia and the Urea Cycle](https://lightmysky.com/learn/science/transamination-ammonia-and-the-urea-cycle-mt_MFu5uQKyFL)