Renin Angiotensin Mechanism.



  • Also known as, Renin-Angiotensin-Aldosterone System (RAAS).

  • The Renin-Angiotensin-Aldosterone System is a hormone system that regulates blood pressure by maintaining fluid balance in the body.

  • Dehydration, Sodium deficiency or hemorrhage are main causes of decreasing circulating plasma levels.

  • Decreased circulating plasma levels cause low Blood Pressure (low BP).

  • Decreased circulating plasma levels stimulate the “Juxtaglomerular apparatus”.

  • Juxtaglomerular apparatus secretes a protein called “Reninin plasma.

  • Renin activates Angiotensinogen, a plasma protein secreted by the liver in plasma to Angiotensin I.

  • On reaching the lungs, the Angiotensin I present in plasma gets converted to the active form Angiotensin II  by action of the enzyme “Angiotensin Converting Enzyme (ACE)”.

  • The formed Angiotensin II acts on Angiotensin II receptors present on the Adrenal gland and releases “Aldosterone”.

  • Aldosterone directly acts on kidneys and ↑ Sodium and water reabsorption.

  • As more water is reabsorbed, circulating plasma volume increases causing increased blood pressure.

  • Angiotensin II also causes vasoconstriction of arterioles causing a direct increase in blood pressure.

  • Various drugs are designed which can interfere with the RAAS, to treat hypertension. (Click here for information on drugs acting on RAAS)

Commonly Asked Question.

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