Nerve and muscle: retrograde neurotrophin signalling: 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: retrograde neurotrophin signalling

Sample item

Sympathetic and small sensory neurones survive only if their targets supply a growth factor that is taken up at the axon terminal. How does the survival signal reach the cell body?

AElectrical conduction along the axonBDiffusion of the factor through the blood to the nucleusCRetrograde axonal transport of the factor bound to its Trk receptorDAnterograde transport of the factor by kinesin

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

The answer and the reasoning

C. Retrograde axonal transport of the factor bound to its Trk receptor

Nerve growth factor released by target tissues binds Trk receptors on the terminal. The complex is internalised and carried to the cell body by dynein-based retrograde transport, where it supports survival and gene expression. Neurones that fail to obtain enough factor undergo apoptosis during development.

Option by option

A. Electrical conduction along the axon
Action potentials do not carry the trophic signal.
B. Diffusion of the factor through the blood to the nucleus
The signal is carried in the axon and not through the blood to the nucleus.
C. Retrograde axonal transport of the factor bound to its Trk receptor (correct)
Correct. Signalling endosomes travel retrogradely on dynein to the soma.
D. Anterograde transport of the factor by kinesin
Kinesin moves cargo anterogradely, away from the cell body.

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, Retrograde axonal transport of the factor bound to its Trk receptor. Nerve growth factor released by target tissues binds Trk receptors on the terminal.

Why is "Electrical conduction along the axon" not the answer?

Action potentials do not carry the trophic signal.

Why is "Diffusion of the factor through the blood to the nucleus" not the answer?

The signal is carried in the axon and not through the blood to the nucleus.

Why is "Anterograde transport of the factor by kinesin" not the answer?

Kinesin moves cargo anterogradely, away from the cell body.

What concept does this question test?

It tests Nerve and muscle: retrograde neurotrophin signalling in Physiology. The complex is internalised and carried to the cell body by dynein-based retrograde transport, where it supports survival and gene expression. Neurones that fail to obtain enough factor undergo apoptosis during development.

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: retrograde neurotrophin signalling?

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.