General anatomy and histology: axon hillock: 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: axon hillock

Sample item

A neuron stained with cresyl violet shows basophilic clumps in the soma and proximal dendrites, but a pale, clump-free cone where the axon leaves the soma. What is this region, and what is its functional importance?

ANode of Ranvier, where the impulse is regeneratedBSynaptic bouton, where transmitter is releasedCDendritic spine, where synaptic inputs are receivedDAxon hillock, where action potentials are initiated

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

The answer and the reasoning

D. Axon hillock, where action potentials are initiated

The axon hillock lacks Nissl substance (rough endoplasmic reticulum). Together with the initial segment, it has a high density of voltage-gated sodium channels and is the usual site where summed inputs trigger the action potential.

Option by option

A. Node of Ranvier, where the impulse is regenerated
Nodes of Ranvier lie along the myelinated axon, away from the soma.
B. Synaptic bouton, where transmitter is released
Boutons lie at the axon terminal and release transmitter.
C. Dendritic spine, where synaptic inputs are received
Dendritic spines receive input and lie on dendrites, not at the origin of the axon.
D. Axon hillock, where action potentials are initiated (correct)
Correct. The Nissl-free hillock and its initial segment is the trigger zone for the action potential.

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, Axon hillock, where action potentials are initiated. The axon hillock lacks Nissl substance (rough endoplasmic reticulum).

Why is "Node of Ranvier, where the impulse is regenerated" not the answer?

Nodes of Ranvier lie along the myelinated axon, away from the soma.

Why is "Synaptic bouton, where transmitter is released" not the answer?

Boutons lie at the axon terminal and release transmitter.

Why is "Dendritic spine, where synaptic inputs are received" not the answer?

Dendritic spines receive input and lie on dendrites, not at the origin of the axon.

What concept does this question test?

It tests General anatomy and histology: axon hillock in Anatomy. Together with the initial segment, it has a high density of voltage-gated sodium channels and is the usual site where summed inputs trigger the action potential.

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: axon hillock?

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.