i can’t scan picture here because of the limitted of this web. you can consult it in www.cvphysiology.com

Renin-Angiotensin-Aldosterone System
There are three important components to this system: 1) renin, 2) angiotensin, and 3) aldosterone
Renin is a proteolytic enzyme that is released into the circulation primarily by the kidneys (Juxtaglomerular (JG) cells) A reduction in afferent arteriole pressure causes the release of renin from the JG cells. Its release is stimulated by:

1. sympathetic nerve activation (acting via β1-adrenoceptors which locates on the JG cells respond to sympathetic nerve stimulation by releasing renin)
2. renal artery hypotension (caused by systemic hypotension or renal artery stenosis)
3. decreased sodium delivery to the distal tubules of the kidney.

When renin is released into the blood, it acts upon a circulating substrate, angiotensinogen, that undergoes proteolytic cleavage to form the decapeptide angiotensin I. Vascular endothelium, particularly in the lungs, has an enzyme, angiotensin converting enzyme (ACE), that cleaves off two amino acids to form the octapeptide, angiotensin II (AII), although many other tissues in the body (heart, brain, vascular) also can form AII

The renin-angiotensin-aldosterone pathway is regulated not only by the mechanisms that stimulate renin release, but it is also modulated by natriuretic peptides (ANP and BNP) released by the heart. These natriuretic peptides acts as an important counter-regulatory system.