Question:medium
Antegrade peristalsis (descending relaxation ahead of the bolus) is due to which one of the following neurotransmitters?
Antegrade peristalsis (descending relaxation ahead of the bolus) is due to which one of the following neurotransmitters?
Show Hint
Antegrade movement needs descending relaxation ahead of the bolus - recall its inhibitory transmitter.
Updated On: Jun 23, 2026
- Acetylcholine
- Serotonin
- Substance P
- VIP
Show Solution
The Correct Option is D
Solution and Explanation
Step 1: Forward gut propulsion works as a two-part reflex: the muscle behind the food contracts while the muscle in front relaxes to make room.
Step 2: The contracting limb above the bolus is cholinergic and excitatory, using acetylcholine together with substance P and neurokinin A.
Step 3: The relaxing limb below the bolus is inhibitory and uses VIP along with nitric oxide and PACAP; this descending relaxation is what lets contents advance in the antegrade direction.
Step 4: Since the question asks for the transmitter responsible for the forward-enabling relaxation, serotonin (a trigger), acetylcholine and substance P (contraction) are excluded, leaving VIP.
\[\boxed{\text{VIP}}\]
Step 2: The contracting limb above the bolus is cholinergic and excitatory, using acetylcholine together with substance P and neurokinin A.
Step 3: The relaxing limb below the bolus is inhibitory and uses VIP along with nitric oxide and PACAP; this descending relaxation is what lets contents advance in the antegrade direction.
Step 4: Since the question asks for the transmitter responsible for the forward-enabling relaxation, serotonin (a trigger), acetylcholine and substance P (contraction) are excluded, leaving VIP.
\[\boxed{\text{VIP}}\]
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