Slide 1Slide 2Slide 3Slide 4Slide 5Slide 6Slide 7Slide 8Slide 9Slide 10The Digestive System:5. Regulation of GI FunctionsThe regulation of motility and secretion, to optimize digestion and absorption, is under complex internal and external control. •Long (cephalic)reflexes integrated in the CNS ( feed forward reflexes; emotional reflexes)•Short reflexes integrated in the enteric nervous system•Reflexes involving the GI peptidesReceptor activation alters digestive activity through neural reflexes and hormonal pathways.•Mechanoreceptors•Chemoreceptors•OsmoreceptorsAnatomically and functionally, the enteric nervous system shares many features with the CNS•Intrinsic neurons + extrinsic neurons = autonomic neurons that bring signals from CNS)•Neurotransmitters and neuromodulators -more than 30 different types•acetylcholin , Substance P -> Stimulation•VIP (vasoactive intestinal peptide), nitric oxide -> Inhibition•Glial support cells•Diffusion Barrier (similar to blood-brain barrier)•Integrating centerThe enteric nervous system can act independently of the CNSThe Enteric Nervous System (“Brain of the Gut”)The Enteric Nervous System (“Brain of the Gut”)MucosaSubmucosaMuscularis externa•ENS can act independently of CNS(peristalsis in lower esophagus;migrating motor complexes)•But normal digestive function requires link to CNS Vagus nerve: esophagus to transv. colon(incl. pancreas and gall baldder)Pelvic nerve: descending colon to anus(autonomic nerves usually synapse first to neurons of ENS), Osmo-receptorsPeristalsis is under control of the ENS+Acetylcholine Substance P-VIPnitric oxide12345Diaphram andabdominal musclesVomiting is under control of the CNSVomiting: Reflex oral expulsion of gastric (and sometimes intestinal) contents through reverse peristalsis and abdominal contraction. e.g.: - overeating -> mechanoreceptors - touch receptors in throate.g.: opiatese.g.: motion sicknessVomiting1237489568(uvula)(lower esophageal sphincter)(antrum)Defecation is under ENS and CNS control P“Urge to defecate”RelaxContract(Skeletal muscle)GI Peptides include Hormones, Neuropeptides, and CytokinesReflexes involving GI