Vestibular disorders: Ewald's first law: practice question

A ENT 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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ENT · Vestibular disorders: Ewald's first law

Sample item

In the horizontal semicircular canal, which direction of endolymph flow produces the strongest stimulation of the hair cells and the greatest increase in firing rate?

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

The answer and the reasoning

D. Ampullopetal flow, towards the ampulla (utriculopetal)

In the horizontal canal, deflection of the cupula towards the utricle (ampullopetal flow) excites hair cells, whereas ampullofugal flow inhibits them. This is Ewald's first law and is the reverse in the vertical canals. It explains the direction of nystagmus in caloric testing.

Option by option

  • A. Flow in the vertical plane only

    The vertical canals have the opposite polarity and are not the horizontal canal.

  • B. Flow in the saccule

    The saccule is an otolith organ and has no endolymph flow of this kind.

  • C. Ampullofugal flow, away from the ampulla

    Ampullofugal flow is inhibitory in the horizontal canal.

  • D. Ampullopetal flow, towards the ampulla (utriculopetal) (correct)

    Correct. In the lateral canal, flow towards the ampulla excites.

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 ENT question

What is the answer to this ENT question?

The best answer is D, Ampullopetal flow, towards the ampulla (utriculopetal). In the horizontal canal, deflection of the cupula towards the utricle (ampullopetal flow) excites hair cells, whereas ampullofugal flow inhibits them.

Why is "Flow in the vertical plane only" not the answer?

The vertical canals have the opposite polarity and are not the horizontal canal.

Why is "Flow in the saccule" not the answer?

The saccule is an otolith organ and has no endolymph flow of this kind.

Why is "Ampullofugal flow, away from the ampulla" not the answer?

Ampullofugal flow is inhibitory in the horizontal canal.

What concept does this question test?

It tests Vestibular disorders: Ewald's first law in ENT. This is Ewald's first law and is the reverse in the vertical canals. It explains the direction of nystagmus in caloric testing.

How hard is this question?

We tag it as a multi-step question: it asks you to combine more than one idea. 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 Vestibular disorders: Ewald's first law?

Learn tuning fork results and audiogram patterns by sketching them. Then use the flashcards and the other ENT 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.