What is the role played by Renin-Angiotensin

When there is a fall in glomerular filtration rate (GFR), they activate the JG cells to release renin which gets converted to angiotensinogen in the blood to angiotensin I

and further to angiotensin II. Angiotensin II is a powerful vasoconstrictor that increases GFR. Angiotensin II is also responsible for activating the adrenal cortex to release

Aldosterone which causes reabsorption of Na+ and water from the distal parts of the tubule leading to an increase in blood pressure and GFR.