Nerve physiology: axonal transport: 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 physiology: axonal transport

Sample item

A farmer bitten by a rabid dog on the hand later develops rabies encephalitis. By which process does the virus travel from the wound to the central nervous system?

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

The answer and the reasoning

C. Fast retrograde axonal transport along microtubules powered by dynein

Rabies virus, herpes simplex virus and tetanus toxin travel from peripheral nerve endings to the cell body by retrograde transport using dynein on microtubules; fast axonal transport runs at roughly 200 to 400 mm per day. Kinesin moves cargo toward the terminal. Slow transport carries cytoskeletal proteins at only a few millimetres per day.

Option by option

  • A. Fast anterograde axonal transport powered by kinesin

    Kinesin moves vesicles and organelles from soma to terminal, the opposite direction.

  • B. Slow axonal transport of cytoskeletal proteins

    Slow transport is far too slow and concerns structural proteins.

  • C. Fast retrograde axonal transport along microtubules powered by dynein (correct)

    Correct. Dynein-based retrograde transport carries the virus to the neuronal cell body.

  • D. Passive diffusion through the axoplasm

    Passive diffusion over such lengths would be far too slow to explain spread.

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 Physiology question

What is the answer to this Physiology question?

The best answer is C, Fast retrograde axonal transport along microtubules powered by dynein. Rabies virus, herpes simplex virus and tetanus toxin travel from peripheral nerve endings to the cell body by retrograde transport using dynein on microtubules; fast axonal transport runs at roughly 200 to 400 mm per day.

Why is "Fast anterograde axonal transport powered by kinesin" not the answer?

Kinesin moves vesicles and organelles from soma to terminal, the opposite direction.

Why is "Slow axonal transport of cytoskeletal proteins" not the answer?

Slow transport is far too slow and concerns structural proteins.

Why is "Passive diffusion through the axoplasm" not the answer?

Passive diffusion over such lengths would be far too slow to explain spread.

What concept does this question test?

It tests Nerve physiology: axonal transport in Physiology. Kinesin moves cargo toward the terminal. Slow transport carries cytoskeletal proteins at only a few millimetres per day.

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 physiology: axonal transport?

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.