General anatomy and histology: Nissl substance: practice question

A Anatomy 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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Anatomy · General anatomy and histology: Nissl substance

Sample item

A motor neuron stained with a basic dye shows dark clumps throughout the cell body and proximal dendrites, but the cone-shaped region where the axon begins is pale. What do the clumps represent?

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

The answer and the reasoning

D. Rough endoplasmic reticulum with free ribosomes

Nissl substance is rough endoplasmic reticulum and polyribosomes, which take up basic dyes because of their RNA content. It is absent from the axon hillock and axon, which is why the hillock looks pale. Loss of Nissl substance (chromatolysis) follows axonal injury.

Option by option

  • A. Stacked Golgi cisternae near the nucleus

    The Golgi apparatus is not basophilic and needs silver or osmium methods to be seen.

  • B. Lipofuscin pigment from lysosomal turnover

    Lipofuscin is a yellow-brown wear pigment, not a basophilic structure.

  • C. Bundles of neurofilaments forming the cytoskeleton

    Neurofilaments are fibrillar and are seen with silver stains, not as basophilic clumps.

  • D. Rough endoplasmic reticulum with free ribosomes (correct)

    Correct. The RNA-rich rough ER and ribosomes make protein and stain basophilic.

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.

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Questions about this Anatomy question

What is the answer to this Anatomy question?

The best answer is D, Rough endoplasmic reticulum with free ribosomes. Nissl substance is rough endoplasmic reticulum and polyribosomes, which take up basic dyes because of their RNA content.

Why is "Stacked Golgi cisternae near the nucleus" not the answer?

The Golgi apparatus is not basophilic and needs silver or osmium methods to be seen.

Why is "Lipofuscin pigment from lysosomal turnover" not the answer?

Lipofuscin is a yellow-brown wear pigment, not a basophilic structure.

Why is "Bundles of neurofilaments forming the cytoskeleton" not the answer?

Neurofilaments are fibrillar and are seen with silver stains, not as basophilic clumps.

What concept does this question test?

It tests General anatomy and histology: Nissl substance in Anatomy. It is absent from the axon hillock and axon, which is why the hillock looks pale. Loss of Nissl substance (chromatolysis) follows axonal injury.

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 General anatomy and histology: Nissl substance?

Learn every nerve by its route, its muscles and what a lesion looks like at the bedside. That one habit answers a large share of questions. Then use the flashcards and the other Anatomy 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.