Understanding RAAS and ADH in Hypotension Control
Kia ora team,
Let's look into the mechanisms of the Renin-Angiotensin-Aldosterone System (RAAS) and Antidiuretic Hormone (ADH) and their roles in regulating blood pressure, particularly in the context of hypotension.
The 3 ways the Renin – Angiotensin Aldosterone System (RAAS) is stimulated are
1 Decreased renal perfusion pressure,
2 Decreased BP causing sympathetic nerves to stimulate the Juxtaglomerular cells of the kidney to release Renin
3 Decreased solute concentration in distal convoluted tubules of the kidneys
RENIN is an enzyme released from the juxtaglomerular cells of the KIDNEYS. This converts ANGIOTENSINOGEN (a protein made by the liver) into ANGIOTENSIN-1.
ANGIOTENSIN CONVERTING ENZYME (ACE) (an enzyme mostly produced by endothelial cells of the lungs) then converts this into ANGIOTENSIN-2.
This molecule has 4 actions:
1 It acts on the arterioles to cause VASOCONSTRICTION.
2 This molecule causes ALDOSTERONE to be released from the Adrenal cortex. This causes INCREASED reabsorption of SODIUM and H2O in the distal convoluted tubules of the KIDNEYS
3 Stimulates the release of ANTIDIURETIC HORMONE/VASOPRESSIN from the posterior pituitary. This hormone is produced by the hypothalamus and it is also stimulated by osmoreceptors in the hypothalamus sensing INCREASED BLOOD OSMOLARITY. It causes VASOCONSTRICTION of blood vessels and increased H2O reabsorption from the collecting ducts of the kidneys
4 It acts on the THIRST centre in the hypothalamus to promote the increased consumption of fluid to increase blood volume
Happy studying