Juxta glomerular Apparatus (JGA) has a complex regulatory role and it controls multihormonal Renin-Angiotensinogen System (RAAS). It responds to decrease in blood pressure in afferent arteriole of glomerulus. Afferent arteriole's cells release an enzyme called renin into blood stream.
Renin converts angiotensinogen present in plasma into angiotensin II peptide. Functions of Angiotensin II :
1. Angiotensin II is a hormone which increases B.P. by causing arterioles to contract.
2. Angiotensin II also increases blood volume in following two ways.
(a) It signals the PCT to absorb more H20 and more NaCl.
(b) It also stimulates adrenal cortex to release aldosterone which induces the DCT to absorb Na+ and water.
Therefore, B.P. and blood volume is increased and it completes the feed back circle.
