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OCR A Biology

Blood Fluid Adh Levels Membrane Water Conc Inorganic

This flashcard explains the negative feedback mechanism of water control in the human body, specifically how ADH affects water reabsorption in the kidneys in response to changes in blood water levels.

Ce flashcard explique le mécanisme de rétroaction négative du contrôle hormonal de l'eau dans le corps humain, en particulier comment l'ADH affecte l'absorption de l'eau dans les reins en réponse aux changements du niveau d'eau dans le sang.

Front Negative feedback control and Mechanism of ADH action
Back
  • When low levels of water; conc of inorganic ions in blood inc and WP of blood/tissue fluid dec and detected by osmoreceptors in hypo, which send impulses to posterior pituitary which releases ADH into blood and carried in blood to cells of collecting duct, binds to receptors on membrane of tubule cells and triggers formation of cAMP (second messenger), which signals vesicles to move and fuse with plasma membrane, which inserts aquaporins (protein-based water channels) in inner wall to inc permeability to water so more reabsorbed into tissue fluid of medulla and blood capillaries by osmosis (low levels of concentrated urine)
  • when high levels of water; conc of inorganic ions in blood dec and WP of blood/tissue fluid inc and detected by osmoreceptors in hypo, which sends less impulses to posterior pituitary which releases less ADH into blood, so less binds to membrane of tubule cells, less cAMP formed, less vesicles fuse with plasma membrane so less aquaporins and less water reabsorbed into tissue fluid of medulla and blood capillaries by osmosis (so large amounts of dilute urine)

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