Small intestine: Edited by David H. Alpers and William F. StensonEnteric nervous system: reflexes, pattern generators and motilityWood, Jackie D Author Information Department of Physiology and Cell Biology and Internal Medicine, College of Medicine, The Ohio State University, Columbus, Ohio, USA Correspondence to Jackie D. Wood, MSc, PhD, FAGA, 304 Hamilton Hall, 1645 Neil Avenue, Columbus, OH 43210-1218, USA Tel: +1 614 292 5449; fax: +1 614 292 4888; e-mail: [email protected] Current Opinion in Gastroenterology: March 2008 - Volume 24 - Issue 2 - p 149-158 doi: 10.1097/MOG.0b013e3282f56125 Buy Metrics Abstract Purpose of review Advances in understanding of the enteric nervous system (ENS) support the brain-in-the-gut concept. Progress relative to sensory neurons, reflex circuits and central pattern generators is summarized. Recent findings A ‘hardwired’ polysynaptic circuit in the ENS evokes descending inhibition of the intestinal circular muscle below an activation point, and contraction of the muscle above the activation point. This circuit occupies the lowest complexity level of the hierarchical organization of neural motility control. Networks in the ENS contain central pattern generators, which activate the ‘hardwired’ basic circuit in recurrent fashion to generate motility patterns linked with intestinal secretion. Summary The dogma that muscle responses seen when the investigator stretches the intestinal wall or stimulates the mucosa reflect a classic reflex can be challenged. No limb equivalent to the afferent limb of a spinal motor reflex has been identified unequivocally in the ENS. Central pattern generators are neural circuits, which generate organized and repetitive motor patterns independent of their sensory input. Central pattern generators rather than afferent-evoked reflexes are postulated to be responsible for the patterns of propulsive contractile behavior and secretion, which recur rhythmically when distension is maintained above threshold or during mucosal application of nutrients or paracrine mediators. © 2008 Lippincott Williams & Wilkins, Inc.