Renin–angiotensin system
hormone system that is involved in the regulation of the plasma sodium concentration and arterial blood pressure
The renin–angiotensin system (RAS), or renin–angiotensin–aldosterone system (RAAS), is a hormone system that regulates blood pressure / fluid / electrolyte balance, and systemic vascular resistance.
When renal blood flow is reduced, juxtaglomerular cells in the kidneys convert the precursor prorenin (already present in the blood) into renin and secrete it directly into the circulation. Plasma renin then carries out the conversion of angiotensinogen, released by the liver, to angiotensin I, which has no biological function on its own. Angiotensin I is subsequently converted to the active angiotensin II by the angiotensin-converting enzyme (ACE) found on the surface of vascular endothelial cells, predominantly those of the lungs. Angiotensin II has a short life of about 1 to 2 minutes. Then, it is rapidly degraded into angiotensin III by angiotensinases which are present in red blood cells and vascular beds in many tissues.
Angiotensin III increases blood pressure and stimulates aldosterone secretion from the adrenal cortex; it has 100% of the adrenocortical stimulating activity and 40% of the vasopressor activity of angiotensin II. Angiotensin IV also has adrenocortical and vasopressor activities.
Angiotensin II is a potent vasoconstrictive peptide that causes blood vessels to narrow, resulting in increased blood pressure. Angiotensin II also stimulates the secretion of the hormone aldosterone from the adrenal cortex. Aldosterone causes the renal tubules to increase the reabsorption of sodium which in consequence causes the reabsorption of water into the blood, while at the same time causing the excretion of potassium (to maintain electrolyte balance).
“Renin–angiotensin system” enters the record as hormone system that is involved in the regulation of the plasma sodium concentration and arterial blood pressure. Crown Archives preserves that source wording while asking what Renin, angiotensin and system can confirm, complicate or overturn.
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