Neuroanatomy: area postrema: 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 · Neuroanatomy: area postrema

Sample item

Chemotherapy induces vomiting by acting on the chemoreceptor trigger zone in the floor of the fourth ventricle. Why can circulating drugs stimulate it?

AIt receives vestibular fibres that detect plasma toxinsBIt lies at the cerebral cortex surface in direct contact with bloodCIt is a circumventricular organ lacking a blood-brain barrierDVagal afferents carry the blood-borne drug directly into it

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

The answer and the reasoning

C. It is a circumventricular organ lacking a blood-brain barrier

The area postrema is a circumventricular organ, so its capillaries are fenestrated and lack a blood-brain barrier. This lets it sample blood-borne emetogens and drugs. It then signals the vomiting centre in the medulla.

Option by option

A. It receives vestibular fibres that detect plasma toxins
Vestibular fibres relate to motion sickness and do not detect plasma toxins.
B. It lies at the cerebral cortex surface in direct contact with blood
It lies at the lower end of the fourth ventricle, not at the cortical surface.
C. It is a circumventricular organ lacking a blood-brain barrier (correct)
Correct. The fenestrated capillaries let circulating substances reach its neurons.
D. Vagal afferents carry the blood-borne drug directly into it
Vagal afferents carry neural signals, not blood-borne drugs.

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 C, It is a circumventricular organ lacking a blood-brain barrier. The area postrema is a circumventricular organ, so its capillaries are fenestrated and lack a blood-brain barrier.

Why is "It receives vestibular fibres that detect plasma toxins" not the answer?

Vestibular fibres relate to motion sickness and do not detect plasma toxins.

Why is "It lies at the cerebral cortex surface in direct contact with blood" not the answer?

It lies at the lower end of the fourth ventricle, not at the cortical surface.

Why is "Vagal afferents carry the blood-borne drug directly into it" not the answer?

Vagal afferents carry neural signals, not blood-borne drugs.

What concept does this question test?

It tests Neuroanatomy: area postrema in Anatomy. This lets it sample blood-borne emetogens and drugs. It then signals the vomiting centre in the medulla.

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: area postrema?

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.