What is the significance of juxta glomerular apparatus (JGA) in kidney function?

The juxta glomerular apparatus in the kidney is a autoregulatory mechanism of GFR. It plays a major role in the regulation of GFR. When the GFR falls, the decrease activates the juxta glomerular cells to release renin which can stimulate the glomerular blood flow. This there by brings back the glomerular filtration rate to normal.