Question

3- Please EXPLAIN the Renin-Angiotensin-Aldosterone axis.

Answer 1

ANS:- Renin-angiotensin-aldosterone system or RAAS is a system that is mainly controlled by three hormones- renin, angiotensin, and aldosterone. This system is mainly activated with low blood pressure.

First, due to low blood pressure blood flow in the kidney also reduce. Reducing blood flow leads to secrete renin hormone (Active form of prorenin) from the juxtaglomerular apparatus cells of the kidney.

Then, renin converts angiotensinogen ( produced by the liver) into the angiotensin-I.

After that, angiotensin-I is converted into the angiotensin-II by an enzyme called angiotensin-converting enzyme. The angiotensin-converting-enzyme is present in lungs capillary.

Then, this angiotensin-II can do two things- i) it can directly work on the blood vessels and can work as a vasoconstrictor. As a result of this blood pressure increase (ii), it stimulates the adrenal gland to secrete aldosterone hormone. Then aldosterone increases the reabsorption of the sodium ions and water. Due to this blood volume and concentration is increased and because of this blood pressure rise.