Solution: The juxtaglomerular apparatus is a sensitive zone created by cellular changes in the distal convoluted tubule and the afferent arteriole at the point where they meet.

The significance of the Juxtaglomerular apparatus is that the renin-angiotensin-aldosterone system (RAAS) is the mechanism by which JGA works. When the glomerular filtration rate drops, the juxtaglomerular apparatus activates, generating renin secretion.

Renin transforms a protein into a peptide, converting angiotensinogen to angiotensin. Angiotensin is a hormone that increases GFR and blood flow in three ways:

1. Increasing the glomerular pressure by narrowing the efferent arterioles.

2. Activating the PCT’s walls in order to reabsorb more water and NaCl

3. Causes the adrenal gland to release aldosterone, which aids in water and sodium reabsorption in the DCT.