Gastrointestinal: rectoanal inhibitory reflex: 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 · Gastrointestinal: rectoanal inhibitory reflex

Sample item

A newborn has delayed passage of meconium and a contracted distal segment on contrast enema. Anorectal manometry shows that rectal distension no longer causes the internal anal sphincter to relax. Which reflex is absent?

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

The answer and the reasoning

A. Rectoanal inhibitory reflex

Rectal distension normally triggers a myenteric reflex that relaxes the internal anal sphincter. In Hirschsprung disease the distal bowel lacks ganglion cells, so this reflex is absent and the segment remains contracted.

Option by option

  • A. Rectoanal inhibitory reflex (correct)

    Correct. The rectoanal inhibitory reflex needs intact myenteric ganglia, which are missing in Hirschsprung disease.

  • B. Enterogastric reflex

    The enterogastric reflex slows gastric emptying when acid or fat enters the duodenum.

  • C. Peristaltic reflex

    The peristaltic reflex is the local propulsive reflex of the gut wall, not the sphincter relaxation.

  • D. Gastrocolic reflex

    The gastrocolic reflex increases colonic motility after a meal.

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 A, Rectoanal inhibitory reflex. Rectal distension normally triggers a myenteric reflex that relaxes the internal anal sphincter.

Why is "Enterogastric reflex" not the answer?

The enterogastric reflex slows gastric emptying when acid or fat enters the duodenum.

Why is "Peristaltic reflex" not the answer?

The peristaltic reflex is the local propulsive reflex of the gut wall, not the sphincter relaxation.

Why is "Gastrocolic reflex" not the answer?

The gastrocolic reflex increases colonic motility after a meal.

What concept does this question test?

It tests Gastrointestinal: rectoanal inhibitory reflex in Physiology. In Hirschsprung disease the distal bowel lacks ganglion cells, so this reflex is absent and the segment remains contracted.

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 Gastrointestinal: rectoanal inhibitory reflex?

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.