Neuroanatomy: ascending tracts: 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.

Try it

Anatomy · Neuroanatomy: ascending tracts

Sample item

Second-order neurons of the dorsal column-medial lemniscus pathway arise in the gracile and cuneate nuclei. A small medullary lesion interrupts their crossing to the opposite side. At which site, and in what form, do these fibres cross?

APons, as the trapezoid bodyBSpinal cord at the level of entry, as the anterior white commissureCThalamus, as the posterior commissureDLower medulla, as internal arcuate fibres

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

The answer and the reasoning

D. Lower medulla, as internal arcuate fibres

Dorsal column first-order axons ascend ipsilaterally in the gracile and cuneate fasciculi and synapse in the nuclei gracilis and cuneatus. Second-order axons sweep ventromedially as internal arcuate fibres, decussate in the lower medulla, and ascend as the medial lemniscus to the ventral posterolateral nucleus of the thalamus.

Option by option

A. Pons, as the trapezoid body
The trapezoid body carries crossing auditory fibres.
B. Spinal cord at the level of entry, as the anterior white commissure
The anterior white commissure is where spinothalamic fibres cross, not the dorsal column.
C. Thalamus, as the posterior commissure
The posterior commissure links pretectal and midbrain areas and is unrelated to this tract.
D. Lower medulla, as internal arcuate fibres (correct)
Correct. Crossing occurs in the lower medulla as internal arcuate fibres.

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 Anatomy question

What is the answer to this Anatomy question?

The best answer is D, Lower medulla, as internal arcuate fibres. Dorsal column first-order axons ascend ipsilaterally in the gracile and cuneate fasciculi and synapse in the nuclei gracilis and cuneatus.

Why is "Pons, as the trapezoid body" not the answer?

The trapezoid body carries crossing auditory fibres.

Why is "Spinal cord at the level of entry, as the anterior white commissure" not the answer?

The anterior white commissure is where spinothalamic fibres cross, not the dorsal column.

Why is "Thalamus, as the posterior commissure" not the answer?

The posterior commissure links pretectal and midbrain areas and is unrelated to this tract.

What concept does this question test?

It tests Neuroanatomy: ascending tracts in Anatomy. Second-order axons sweep ventromedially as internal arcuate fibres, decussate in the lower medulla, and ascend as the medial lemniscus to the ventral posterolateral nucleus of the thalamus.

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 Neuroanatomy: ascending tracts?

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.