Direct and indirect activation
Intrinsic nervous system
Gastrointestinal motility is enhanced by stimulation of cholinergic receptors located in the smooth and long muscle layers. Stimulation can occur both directly (extrinsic stimulation of the cholingergic receptors) or indirectly (intrinsic stimulation of the myenteric plexus and then the
cholinergic receptors). The myenteric plexus can be stimulated by neuronal factors (i.e. serotonin, dopamine), neurocrines (i.e. substance P, motilin, cholecystokinin) and GI peptides (i.e. gastrin, VIP).
The effects of the various nervous systems are as follows:
Which of the following is a compound for inhibitory neurons in ENS:
Extra info: Most substances in the GI are peptides which stimulate activity. In general, only nitric oxide is inhibitory.