two ganglionated neural plexuses in the gut wall which form one of the three major divisions of the autonomic nervous system; the enteric nervous system innervates the gastrointestinal tract, the pancreas, and the gallbladder; it contains sensory neurons, interneurons, and motor neurons, thus the circuitry can autonomously sense the tension and the chemical environment in the gut and regulate blood vessel tone, motility, secretions, and fluid transport; the system is itself governed by the central nervous system and receives both parasympathetic and sympathetic innervation.