Respiratory system: vagal reflexes: 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 · Respiratory system: vagal reflexes

Sample item

After bilateral cervical vagotomy in an experimental animal, breathing becomes slow and deep. Loss of which reflex best explains this change in breathing pattern?

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

The answer and the reasoning

D. Hering-Breuer inflation reflex

Slowly adapting stretch receptors in the bronchial smooth muscle send vagal afferents to the medulla and switch off inspiration when the lungs are inflated. After vagotomy this brake is lost, so inspiration lasts longer and breathing becomes slower and deeper. The reflex is weak in resting adult humans and more important in neonates and during exercise.

Option by option

  • A. Cushing reflex

    The Cushing reflex is hypertension and bradycardia from raised intracranial pressure.

  • B. Bainbridge reflex

    The Bainbridge reflex is atrial stretch causing tachycardia, not a respiratory reflex.

  • C. Carotid body chemoreflex

    The carotid body chemoreflex travels in the glossopharyngeal nerve, which is spared by vagotomy.

  • D. Hering-Breuer inflation reflex (correct)

    Vagal pulmonary stretch afferents limit tidal volume, so their loss slows and deepens breathing.

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, Hering-Breuer inflation reflex. Slowly adapting stretch receptors in the bronchial smooth muscle send vagal afferents to the medulla and switch off inspiration when the lungs are inflated.

Why is "Cushing reflex" not the answer?

The Cushing reflex is hypertension and bradycardia from raised intracranial pressure.

Why is "Bainbridge reflex" not the answer?

The Bainbridge reflex is atrial stretch causing tachycardia, not a respiratory reflex.

Why is "Carotid body chemoreflex" not the answer?

The carotid body chemoreflex travels in the glossopharyngeal nerve, which is spared by vagotomy.

What concept does this question test?

It tests Respiratory system: vagal reflexes in Physiology. After vagotomy this brake is lost, so inspiration lasts longer and breathing becomes slower and deeper. The reflex is weak in resting adult humans and more important in neonates and during exercise.

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 Respiratory system: vagal reflexes?

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.