Zusammenfassung der Ressource
Renin - Angiotensin - Aldosterone System
- Juxtaglomerular cells secrete renin
- 3 factors are involved in activating renin secretion:
- 1.) PERFUSION PRESSURE - a decrease in perfusion pressure causes renin secretion
- 2.) SYMPATHETIC NERVE ACTIVITY - increased activity of SNS that innervates afferent arterioles increases renin secretion
- 3.) DELIVERY OF NaCl TO THE MACULA DENSA - a decrease in NaCl to the macula densa activates renin secretion
- Activated when ECF volume decreases and causes an increase in Na reabsorption
- Increasing Na in ECF draws in water by osmosis to return ECF volume to normal
- Indirectly causes reabsorption of Cl aswell as it is drawn across tight junctions by Em
- Renin cleaves angiotensin ( a liver derived protein) to produce angiotensin I which is further cleaved by the converting enzyme ACE in the lungs to angiotensin II
- Angiotensin II stimulates AT1 receptors to cause secretion of aldosterone from adrenal cortex
- Aldosterone stimulates the NaK ATPase in the basolateral membrane and the Na channel in the apical membrane of principal cells in the collecting duct
- Angiotensin II stimluates activity and insertion of NaH antiporter in proximal tubule cells to up-regulate Na reabsorption