What causes the release of renin from the juxtaglomerular apparatus?

• A. Increased blood volume in the renal veins
• B. High blood pressure in the efferent arterioles
• C. Decreased blood pressure in the afferent arterioles
• D. Increased sodium concentration in the distal tubule

Answer: (C)

Verified step by step guidance

1. Understand the role of the juxtaglomerular apparatus (JGA) in the kidney. It is responsible for regulating blood pressure and fluid balance through the release of renin.
2. Recognize that renin is an enzyme that initiates the renin-angiotensin-aldosterone system (RAAS), which helps to increase blood pressure and sodium retention.
3. Identify the triggers for renin release. The JGA releases renin primarily in response to decreased blood pressure in the afferent arterioles, which are the blood vessels supplying the glomerulus.
4. Consider the physiological mechanism: When blood pressure in the afferent arterioles decreases, the JGA senses this change and responds by releasing renin to restore normal blood pressure.
5. Note that other factors such as decreased sodium concentration in the distal tubule can also stimulate renin release, but the primary trigger in this context is decreased blood pressure in the afferent arterioles.