Respiratory system: medullary rhythm generation: 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: medullary rhythm generation

Sample item

A man given a large intravenous dose of morphine breathes slowly and then becomes apnoeic. Which site, rich in mu-opioid receptors, contains the neurons that generate the basic respiratory rhythm?

APre-Botzinger complex in the ventrolateral medullaBPneumotaxic centre in the upper ponsCApneustic centre in the lower ponsDNucleus of the tractus solitarius

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

The answer and the reasoning

A. Pre-Botzinger complex in the ventrolateral medulla

The pre-Botzinger complex is the main inspiratory rhythm generator, and opioids suppress it, causing slow, shallow breathing and apnoea. The pontine centres modulate the pattern, and the nucleus of the tractus solitarius mainly relays afferents from the lungs and chemoreceptors.

Option by option

A. Pre-Botzinger complex in the ventrolateral medulla (correct)
Correct. Opioids depress the pre-Botzinger rhythm generator.
B. Pneumotaxic centre in the upper pons
The pneumotaxic centre limits inspiration and increases rate but does not generate the rhythm.
C. Apneustic centre in the lower pons
The apneustic centre prolongs inspiration and is not the rhythm source.
D. Nucleus of the tractus solitarius
The nucleus of the tractus solitarius is a sensory relay, forming part of the dorsal respiratory group.

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 Physiology question

What is the answer to this Physiology question?

The best answer is A, Pre-Botzinger complex in the ventrolateral medulla. The pre-Botzinger complex is the main inspiratory rhythm generator, and opioids suppress it, causing slow, shallow breathing and apnoea.

Why is "Pneumotaxic centre in the upper pons" not the answer?

The pneumotaxic centre limits inspiration and increases rate but does not generate the rhythm.

Why is "Apneustic centre in the lower pons" not the answer?

The apneustic centre prolongs inspiration and is not the rhythm source.

Why is "Nucleus of the tractus solitarius" not the answer?

The nucleus of the tractus solitarius is a sensory relay, forming part of the dorsal respiratory group.

What concept does this question test?

It tests Respiratory system: medullary rhythm generation in Physiology. The pontine centres modulate the pattern, and the nucleus of the tractus solitarius mainly relays afferents from the lungs and chemoreceptors.

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: medullary rhythm generation?

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.