Gastrointestinal Tract enteric nervous system:

The gastrointestinal tract has its own local nervous system known as enteric nervous system in the form of two nerve networks, the  myenteric plexus and the submucosal plexus.  These neurons either synapse with other neurons or end near smooth muscles, glands and epithelial cells. Many axons leave the myenteric plexus and synapse with neurons in the submucosal plexus, and vice vera, so that neural activity in one plexus influences the activity in the other. Moreover, stimulation at one point in the plexus can lead to impulses that are conducted both up and down the tract. The myenteric plexus influences smooth muscle activity whereas the submucosal plexus influences secretory activity.

The enteric nervous system contains adrenergic and cholinergic neurons as well as neurons that release other neurotransmitters such as nitric oxide, several neuropeptides and ATP.

Muscle cells and exocrine glands- are supplied by neurons that are part of the enteric nervous system. This permits neural reflexes that are completely within the tract- that is, independent of the CNS. In addition, nerve fibers from both the sympathetic and parasympathetic branches of the autonomic nervous system enter the intestinal tract and synapse with neurons in both plexuses. Via these pathways, the CNS can influences the motility and secretory activity of the gastrointestinal tract.

Thus, two types of neural-reflex arcs exist:

1) Short reflexes from receptors through the nerve plexuses to effector cells and;

2) Long reflexes from receptors in the tract to the CNS by way of afferent nerves, and back to the nerve plexuses and effector cells by way of autonomic nerve fibers.