Renal physiology: tubuloglomerular feedback: practice question

A Physiology question in the style of the NEET PG paper. Answer it first, then read why the right option is right and why each of the others is wrong.

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Physiology · Renal physiology: tubuloglomerular feedback

Sample item

When sodium chloride delivery to the distal tubule rises, what does the macula densa do to restore the glomerular filtration rate towards normal?

AIt releases aldosterone from the adrenal cortex directlyBIt signals dilation of the afferent arteriole, increasing glomerular filtrationCIt signals constriction of the afferent arteriole, reducing glomerular filtrationDIt stimulates renin release from the efferent arteriole

Original practice item, not a recalled exam question. Nothing here is recorded.

The answer and the reasoning

C. It signals constriction of the afferent arteriole, reducing glomerular filtration

High distal sodium chloride delivery signals that filtration is excessive. Macula densa cells release mediators such as adenosine that constrict the afferent arteriole, lowering the glomerular filtration rate. Low delivery does the opposite and also stimulates renin release.

Option by option

A. It releases aldosterone from the adrenal cortex directly
Aldosterone is released by the adrenal cortex in response to angiotensin II and potassium, not directly by the macula densa.
B. It signals dilation of the afferent arteriole, increasing glomerular filtration
Dilation would increase filtration further and is the response to low delivery.
C. It signals constriction of the afferent arteriole, reducing glomerular filtration (correct)
Correct. Afferent constriction reduces filtration when delivery is high.
D. It stimulates renin release from the efferent arteriole
Renin is released by juxtaglomerular granular cells, and mainly when delivery is low.

Source note: Original NextPrep sample item — pending expert review. This item is original practice material awaiting independent expert review, so confirm important facts in a standard textbook.

Questions about this Physiology question

What is the answer to this Physiology question?

The best answer is C, It signals constriction of the afferent arteriole, reducing glomerular filtration. High distal sodium chloride delivery signals that filtration is excessive.

Why is "It releases aldosterone from the adrenal cortex directly" not the answer?

Aldosterone is released by the adrenal cortex in response to angiotensin II and potassium, not directly by the macula densa.

Why is "It signals dilation of the afferent arteriole, increasing glomerular…" not the answer?

Dilation would increase filtration further and is the response to low delivery.

Why is "It stimulates renin release from the efferent arteriole" not the answer?

Renin is released by juxtaglomerular granular cells, and mainly when delivery is low.

What concept does this question test?

It tests Renal physiology: tubuloglomerular feedback in Physiology. Macula densa cells release mediators such as adenosine that constrict the afferent arteriole, lowering the glomerular filtration rate. Low delivery does the opposite and also stimulates renin release.

How hard is this question?

We tag it as an application question: it asks you to use a fact on a patient or a finding. The tag is our own editorial judgement, not an official difficulty rating, so read the reason for every option, not only the answer.

How should I study Renal physiology: tubuloglomerular feedback?

For each system, sketch the key graph (pressure–volume loop, oxygen dissociation curve, nephron handling) and explain it aloud. Then use the flashcards and the other Physiology questions on this site to test what stuck.

Is this a real NEET PG question?

No. It is an original practice item (editorial status: sample, version 1). NextPrep does not publish recalled or leaked questions, and independent faculty review of this item has not been completed yet, so confirm important facts in a standard textbook.