Question:medium
The primary action of nitric oxide (NO) in the gastrointestinal tract is?
The primary action of nitric oxide (NO) in the gastrointestinal tract is?
Show Hint
NO is the NANC inhibitory transmitter that relaxes gut muscle ahead of the bolus.
Updated On: Jun 24, 2026
- Vasodilatation
- Vasoconstriction
- GI smooth muscle relaxation
- Slow smooth muscle contraction
Show Solution
The Correct Option is C
Solution and Explanation
Nitric oxide is the same molecule once described as endothelium-derived relaxing factor. Wherever it is released, its signalling endpoint is similar: it enters smooth muscle, stimulates guanylate cyclase to raise cGMP, and the resulting fall in cytosolic calcium relaxes the muscle.
The question asks specifically about the gut, so the relevant context is enteric motility rather than the vasculature. When food distends a segment of intestine, the enteric nervous system organises a coordinated reflex: the muscle just behind the bolus contracts while the muscle just ahead of it relaxes, propelling contents forward.
That forward (descending) relaxation is driven by inhibitory enteric neurons whose transmitters include nitric oxide, vasoactive intestinal peptide and ATP. These are classic non-adrenergic, non-cholinergic (NANC) signals, and NO is the principal inhibitory mediator producing relaxation of gastrointestinal smooth muscle.
While NO certainly causes vasodilatation in blood vessels, the option set is asking for its dominant role within the GI tract itself, which is to relax the smooth muscle of the gut wall.
\[\boxed{\text{GI smooth muscle relaxation}}\]
The question asks specifically about the gut, so the relevant context is enteric motility rather than the vasculature. When food distends a segment of intestine, the enteric nervous system organises a coordinated reflex: the muscle just behind the bolus contracts while the muscle just ahead of it relaxes, propelling contents forward.
That forward (descending) relaxation is driven by inhibitory enteric neurons whose transmitters include nitric oxide, vasoactive intestinal peptide and ATP. These are classic non-adrenergic, non-cholinergic (NANC) signals, and NO is the principal inhibitory mediator producing relaxation of gastrointestinal smooth muscle.
While NO certainly causes vasodilatation in blood vessels, the option set is asking for its dominant role within the GI tract itself, which is to relax the smooth muscle of the gut wall.
\[\boxed{\text{GI smooth muscle relaxation}}\]
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