Question

What role do the kidneys play in the RAAS and BNP system?

Answer 1

Renin–Angiotensin–Aldosterone System (RAAS) start from the kidney to regulates the blood pressure. BNP (brain natriuretic peptide) system have inhibitory effects on RAAS of kidney. Both are involved in regulation of body fluid and blood pressure through kidney

When blood pressure decreases, less blood flow through the kidney results in release of renin (an enzyme) from juxtaglomerular apparatus of the kidney. This renin catalyzes the conversion of angiotensinogen to angiotensin I. Angiotensin converting enzyme from the lung catalyzes the conversion of angiotensin I to angiotensin II. Angiotensin II have two main functions

• Angiotensin II is a potent vasoconstrictor causes vasoconstriction result in elevation of blood pressure
• Angiotensin II stimulates the adrenal cortex to release aldosterone which increases reabsorption of water and sodium in the kidney result increases blood volume thereby blood pressure

Increases tension on heart and blood vessels due to high blood volume stimulates heart and blood vessels to release  BNP. BNP has inhibitory effects on RAAS. BNP decreases Aldosterone secretion causes less water reabsorption and more water elimination, BNP causes vasoconstriction, and BNP also inhibits the secretion of renin bu kidney there by RAAS system stop. This all ultimately leads to decreases in blood pressure to the normal