Question #333

Which of the following statements regarding the action of chemical mediators in the gut is true?

the effect of acetylcholine is primarily inhibitory

secretin promotes gastric motility

vasoactive intestinal polypeptide (VIP) relaxes gastrointestinal smooth muscle

cholecystokinin promotes gastric emptying

the effect of noradrenaline is predominantly excitatory

VIP is a key parasympathetic mediator and has a potent relaxing effect on gastrointestinal smooth muscle.

Sympathetic activity, and therefore the effect of noradrenaline, is predominantly inhibitory in the gut: sympathetic activation is associated with a state of autonomic arousal in which gastrointestinal activity is not the first priority. As a counter point, parasympathetic activity and therefore the effect of acetylcholine is predominantly excitatory.

Secretin and cholecystokinin inhibit gastric emptying, allowing additional time for gastric juice to act on food.

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