Emergency Medical Technician (EMT) Intermediate Practice Exam

What does the renin-angiotensin system in the kidneys help to regulate?

1. Fluid balance in the body

2. Electrolyte levels

3. Blood pressure

4. Red blood cell production

The correct answer is: Blood pressure

The renin-angiotensin system is a critical hormonal system that plays a vital role in regulating blood pressure. When blood pressure drops, specialized cells in the kidneys detect this decrease and release the enzyme renin. Renin then converts angiotensinogen, a protein produced by the liver, into angiotensin I. Subsequently, angiotensin-converting enzyme (ACE), primarily found in the lungs, converts angiotensin I into angiotensin II, a potent vasoconstrictor. Angiotensin II has several important effects: it narrows blood vessels, which increases peripheral resistance and, subsequently, blood pressure. Additionally, it stimulates the adrenal glands to release aldosterone, promoting sodium and water reabsorption in the kidneys. This retention of fluid further contributes to increased blood volume and blood pressure. Thus, the primary role of the renin-angiotensin system centers on the regulation of blood pressure, making it an essential mechanism in the body’s response to hypotension (low blood pressure). While fluid balance and electrolyte levels are indeed influenced by the activities of the renin-angiotensin system, its primary and most direct function pertains to the regulation of blood pressure.