RENIN-ANGIOTENSIN SYSTEM::
This is one of the most important system regulating blood pressure in many instances it has been shown that high blood pressure is correlated with high renin levels in the blood
Renin is a protein secreted by juxtaglomerular cells of the kidney these are the specialized cells found in the afferent arteriole and the Distal tubules near the glomerulus the secretion occurs in response to decrease in renal perfusion pressure mechanical stress hypoglycemia exercise emotional stress etc the decrease in perfusion pressure may again be due to decrease in extracellular fluid and volume changes
Activation of adrenoceptors present on the juxtaglomerular cells may cause renin release Atrial Natriuretic peptide causes a decrease in renin release increase in Na reabsorption at macula densa and increase in blood pressure in pre -glomerular vessels cause a decrease in renin release
The renin thus released activates angiotensinogen (a y globulin formed in liver and found in plasma) to form angiotensin I This angiotensin is an inactive decapeptide and gets converted into angiotensin II by the angiotensin converting enzyme (ACE)
The angiotensin II acts on adrenal cortex to initiate the aldosterone secretion which causes sodium retention and vasoconstriction Angiotensin II by itself also produces vasoconstriction The resultant effect is a rise in arterial blood pressure This rise in arterial blood pressure inhibits renin release and hence the blood pressure is controlled
0 Comments