Question

Which of the following best describes the sympathetic pathway's effect on the glomerulus in the kidney?

• A. Sympathetic stimulation causes vasodilation of the afferent arteriole, increasing glomerular filtration rate (GFR).
• B. Sympathetic stimulation causes vasoconstriction of the afferent arteriole, decreasing glomerular filtration rate (GFR).
• C. Sympathetic stimulation has no effect on the glomerulus.
• D. Sympathetic stimulation causes vasodilation of the efferent arteriole, decreasing glomerular filtration rate (GFR).

Hint:

The sympathetic nervous system reduces GFR by causing vasoconstriction of the afferent arteriole, helping conserve water and maintain blood pressure.

Answer 1

The Correct Option is B

Step 1: Understanding the sympathetic response.
Sympathetic stimulation is part of the "fight or flight" response, which prioritizes blood flow to vital organs (e.g., muscles and brain) by reducing blood flow to the kidneys. Step 2: Effect on the glomerulus.
Sympathetic stimulation causes vasoconstriction of the afferent arteriole. This reduces blood flow into the glomerulus, leading to a decreased glomerular filtration rate (GFR). This response helps conserve water and maintain blood pressure during stress. Step 3: Explanation of other options.
Option (A): Incorrect. Vasodilation of the afferent arteriole would increase GFR, which is opposite to the sympathetic response. Option (B): Correct. Vasoconstriction of the afferent arteriole decreases GFR during sympathetic stimulation. Option (C): Incorrect. Sympathetic stimulation significantly affects renal blood flow and GFR. Option (D): Incorrect. Vasodilation of the efferent arteriole would decrease filtration pressure, but this is not a typical sympathetic response. \text {The correct answer is: } \text{Sympathetic stimulation causes vasoconstriction of the afferent arteriole, decreasing GFR.}