reniiniangiotensiinaldosteronijärjestelmään

The renin-angiotensin-aldosterone system, often abbreviated as RAAS, is a complex hormonal cascade that plays a crucial role in regulating blood pressure and fluid balance in the body. It is primarily activated when blood pressure drops, or when the body detects a decrease in sodium levels. The system begins in the kidneys, where the enzyme renin is released in response to these stimuli.

Renin then acts on angiotensinogen, a protein produced by the liver, converting it into angiotensin I. Angiotensin I is relatively inactive, but as it travels through the bloodstream, it encounters another enzyme called angiotensin-converting enzyme (ACE), which is found mainly in the lungs. ACE transforms angiotensin I into angiotensin II.

Angiotensin II is a potent vasoconstrictor, meaning it narrows blood vessels, which directly increases blood pressure. It also stimulates the adrenal glands to release aldosterone. Aldosterone acts on the kidneys, promoting the reabsorption of sodium and water back into the bloodstream, which further contributes to increasing blood volume and, consequently, blood pressure. Additionally, angiotensin II can influence thirst and the release of antidiuretic hormone (ADH), both of which help conserve water. Through these combined actions, the RAAS effectively works to restore blood pressure to normal levels.