Final answer:
The renin-angiotensin-aldosterone system (RAS) regulates blood pressure by causing the release of renin from the kidneys, which initiates a cascade resulting in the production of angiotensin II. Angiotensin II increases blood pressure and volume through vasoconstriction, aldosterone release, and ADH secretion. Medications called ACE inhibitors can regulate high blood pressure by interfering with this system.
Step-by-step explanation:
The renin-angiotensin-aldosterone system (RAS) plays a crucial role in regulating arterial pressure, specifically in controlling blood pressure and blood volume. When the kidneys detect decreased blood pressure, specialized cells known as juxtaglomerular (JG) cells release the enzyme renin.
Renin then catalyzes the conversion of angiotensinogen—a protein produced by the liver—into angiotensin I. In the lungs, angiotensin I is further converted into the potent vasoconstrictor angiotensin II by the angiotensin-converting enzyme (ACE).
Angiotensin II raises blood pressure by constricting blood vessels, stimulating the secretion of aldosterone from the adrenal cortex, and triggering the release of anti-diuretic hormone (ADH) from the hypothalamus leading to water retention in the kidneys.
Aldosterone released in response to angiotensin II prompts the kidneys to reabsorb more sodium, which in turn increases blood volume and pressure. Furthermore, angiotensin II decreases the glomerular filtration rate (GFR) in the nephrons, which also contributes to the regulation of fluid balance. Overall, the RAS system stabilizes blood pressure by adjusting the volume of blood flowing through the circulatory system.
In medical practice, the regulation of blood pressure can be achieved using drugs that inhibit ACE, known as ACE inhibitors, demonstrating the importance of the RAS in controlling hypertension.