Reflex pathways within the enteric nervous system regulate contraction of the muscle, epithelial secretion, and blood flow. Interconnecting neural fibers between the myenteric and submucous plexuses coordinate this activity. The identification of neurons that participate in reflex arcs as sensory neurons, interneurons, or motor neurons is continually evolving with the discovery of new peptides and other substances. Mediators released from endocrine cells, immunocytes, or other cell types modulate the epithelial secretory response by acting directly on epithelial cells or on their innervation.