Question

WRITE AN ESSAY ON THE RENIN-ANGIOTENSIN-ALDOSTERONE SYSTEM

Answer 1

Answer:

Renin-Angiotensin-Aldosterone System (RAAS) is one of the major regulatory mechanisms to control and monitor the functions of the kidneys by the assistance of multiple important hormones.

This system becomes functional upon the drop in the blood pressure within the glomerulus of the renal corpuscle such that the glomerular filtration gets impaired and also the rate of urine formation.

In response to the drop in the blood pressure, the juxtaglomerular cells (JG cells) of the JG apparatus release an enzyme; Renin. The cells are called as JG cells because of their close proximity to the glomerulus (a network of the blood capillaries). The hormone Renin is responsible for changing an inactive plasma protein Angiotensinogen released by the liver to angiotensin II. The angiotensin II leads to the contraction of the arterioles and due to this the blood pressure within them increases. The hormone Angiotensin II also stimulates the cortex region of the adrenal glands to release the hormone aldosterone. The hormone aldosterone is known to stimulate the distal convoluted tubules of the renal tubular segment of the nephron to absorb more amounts of Na+ ions and water.

Thus, the overall function of the RAAS system is to;

a) Increase the blood pressure within the arterioles and

b) Increase the blood volume by reabsorbing more amounts of NaCl and water within the renal tubular segments of the nephron

The system becomes functional in response to a pressure drop within the arterioles of the glomerulus. And again, since the metabolism means to regulate the complete processes within the body; the increased pressure again needs to be counteracted. It is for that reason that the action of RAAS is counteracted by the Atrial Natriuretic Factor (ANF) which is released by the walls of the atria of the human heart. The peptide hormone ANF opposes the RAAS and hence the blood volume, osmolarity and the blood pressure with which the urine gets formed within the kidneys gets effectively monitored.