Question

Make a schematic diagram on the activation of renin–angiotensin–aldosterone system.

Answer 1

RAAS (RENIN ANGIOTENSION-ALDESTERON SYSTEM)

It a hormonal system consist of renin, angiotensin II and aldosterone to control the renal flow. It is essentially for regulation of blood flow and fluid balance in the body

Let’s discus it step by step

1. Release of renin from the juxtaglomerular apparatus is the first step in the response of:

a. Reduce sodium level

b. Reduce perfusion pressure detected by baroreceptor

c. Sympathetic stimulation of JGA by beta-adrenergic.

Release of renin is inhibited by ANP (Atrial natriuretic peptide) release by stretched atria in response of increase blood pressure.

2. Angiotensin is the precursor protein in the liver and cleaved by renin to form Angiotensin, angiotensin I is converting into angiotensin II by Angiotensin converting enzymes released by endothelial cell of lungs and kidney.

3. Angiotensin II is bind to G-protein couples’ receptor, AT1 and AT2 receptor and causes

a. Constriction of arterioles

b. Na+ reabsorption in the kidney

c. Increase release of noradrenaline

d. Act on adrenal gland and stimulate the release of aldosterone

e. Act on hypothalamus and stimulate the release of ADH.

4. Angiotensin II act on the adrenal gland and stimulate the release of aldosterone. Aldosterone act on the principle cells of collecting duct leads to reabsorption of Na+ from the filtrate and potassium is released from the blood and exit in the urine.

MAP- mean arterial pressure

ADH- antidiuretic harmone

SNS- sympathetic nervous system

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