Neurophysiology: tonic and phasic receptors: 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 · Neurophysiology: tonic and phasic receptors

Sample item

A blind person reads Braille using the fingertip, feeling edges and points of raised dots with sustained pressure. Which receptors mainly signal this?

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

The answer and the reasoning

D. Merkel discs, which are slowly adapting

Merkel discs are slowly adapting tonic receptors with small receptive fields that resolve edges, points and texture and signal sustained pressure. Pacinian and Meissner corpuscles are rapidly adapting phasic receptors, responding to vibration and flutter and to light moving touch. Rapidly adapting receptors signal changes rather than maintained stimuli.

Option by option

  • A. Meissner corpuscles, which are slowly adapting

    Meissner corpuscles are rapidly adapting, not slowly adapting.

  • B. Free nerve endings, which are rapidly adapting

    Free nerve endings mediate pain and temperature and are not the main receptors for fine spatial discrimination.

  • C. Pacinian corpuscles, which are rapidly adapting

    Pacinian corpuscles respond to deep vibration and have large receptive fields.

  • D. Merkel discs, which are slowly adapting (correct)

    Correct. Slowly adapting receptors report fine spatial detail during sustained contact.

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 Physiology question

What is the answer to this Physiology question?

The best answer is D, Merkel discs, which are slowly adapting. Merkel discs are slowly adapting tonic receptors with small receptive fields that resolve edges, points and texture and signal sustained pressure.

Why is "Meissner corpuscles, which are slowly adapting" not the answer?

Meissner corpuscles are rapidly adapting, not slowly adapting.

Why is "Free nerve endings, which are rapidly adapting" not the answer?

Free nerve endings mediate pain and temperature and are not the main receptors for fine spatial discrimination.

Why is "Pacinian corpuscles, which are rapidly adapting" not the answer?

Pacinian corpuscles respond to deep vibration and have large receptive fields.

What concept does this question test?

It tests Neurophysiology: tonic and phasic receptors in Physiology. Pacinian and Meissner corpuscles are rapidly adapting phasic receptors, responding to vibration and flutter and to light moving touch. Rapidly adapting receptors signal changes rather than maintained stimuli.

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 Neurophysiology: tonic and phasic receptors?

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.