Regulation of homeostasis by the kidney: fluid balance Flashcards
What is a consequence of having too much water
Drinking too much water may lead to fluid overload that disrupts the bodies water and electrolyte balance and can cause cerebral oedema’s that can lead to death
How does ADH increase water retention
ADH acts on V2 receptors in the basolateral membrane of principal cells in the collecting duct which leads to insertion of aquaporin-2 water channels into the apical surface.
Outline the mechanism of ADH action
ADH interacts with a G-protein coupled receptor which stimulates a subunit called G. simulatory subunit which activates adenylate cyclase that converts ATP into cyclic-AMP which leads to activation of protein kinase A which phosphorylates aquaporin 2 water channels that leads to their expression into the surface of the cell.
What is ADH released in response to?
It is released in response to changes in plasma osmolality and ECV. These changes are detected by osmoreceptors and baroreceptors.
What are two pathways in which osmolality is regulated
ADH—> affects the kidneys—-> renal excretion of water affected
Thirst—> affects the brain: drinking behaviour—-> affects water intake.
Outline how ECV is regulated
ECV is regulated by ADH, RAAS, ANP and SNS. the short term effects are on the Blood vessels to affect BP but long term effects are on kidneys to affect Na excretion.
What are short term and long term effects of ANG-2
short term; vasoconstriction of renal and other systemic vessels and more sodium reabsorption.
long term effects: ang2 causes renal cell hypertrophy
What is ANP
Atrial natriuretic peptide is released by the atrial myocytes in response to raised ECV by detecting the atrial stretch and it promotes Na+ excretion and renal vasodilation to increase GFR so more Na is excreted.
