Nerve and muscle: myelination in CNS and PNS: 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 · Nerve and muscle: myelination in CNS and PNS

Sample item

In a patient with a demyelinating disease of the optic nerve, loss of which cell's processes explains the conduction defect, given that one such cell can myelinate segments of several axons?

ASchwann cellBOligodendrocyteCAstrocyteDSatellite cell

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

The answer and the reasoning

B. Oligodendrocyte

In the CNS, one oligodendrocyte extends several processes and myelinates segments of many axons. In the peripheral nervous system, each Schwann cell myelinates a single segment of one axon. Multiple sclerosis targets oligodendrocyte myelin, leading to slowed or blocked saltatory conduction.

Option by option

A. Schwann cell
A Schwann cell myelinates one segment of one peripheral axon, and the optic nerve is part of the CNS.
B. Oligodendrocyte (correct)
Correct. One oligodendrocyte myelinates segments of many CNS axons.
C. Astrocyte
Astrocytes support neurons and the blood-brain barrier and do not form myelin.
D. Satellite cell
Satellite cells surround neuronal cell bodies in ganglia and do not make myelin.

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 B, Oligodendrocyte. In the CNS, one oligodendrocyte extends several processes and myelinates segments of many axons.

Why is "Schwann cell" not the answer?

A Schwann cell myelinates one segment of one peripheral axon, and the optic nerve is part of the CNS.

Why is "Astrocyte" not the answer?

Astrocytes support neurons and the blood-brain barrier and do not form myelin.

Why is "Satellite cell" not the answer?

Satellite cells surround neuronal cell bodies in ganglia and do not make myelin.

What concept does this question test?

It tests Nerve and muscle: myelination in CNS and PNS in Physiology. In the peripheral nervous system, each Schwann cell myelinates a single segment of one axon. Multiple sclerosis targets oligodendrocyte myelin, leading to slowed or blocked saltatory conduction.

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 Nerve and muscle: myelination in CNS and PNS?

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.