1、Gastrointestinal system,Xiang-Yao LI, PhDDepartment of PhysiologyZhejiang University School of MedicineEmail: ,Alimentary CanalContinuous, muscular digestive tube winding throughout the bodyDigests and absorbs food particlesContains the following organs:Mouth,Pharynx,Esophagus, Stomach, Small Intest
2、ine Large IntestineAccessory Digestive OrgansContains the following organs:Teeth, Tongue,Salivary GlandsLiver,Gallbladder,Pancreas,General properties of gastrointestinal smooth muscle,Low excitabilityHigh distensibilityTonic contractionAutorhythmicityHigh sensitivity to temperature, stretch and chem
3、ical stimulation,Electrophysiological properties of gastrointestinal smooth muscle,Resting membrane potential-40-80 mVIonic basisEm (selective membrane permeability to K+, Na+, Cl- and Ca2+)Electrogenic Na+-K+ pump,Slow wave (basic electrical rhythm)The spontaneous rhythmic, subthreshold depolarizat
4、ions of the cell membrane (slow wave) of the gastrointestinal tract that characterizes the underlying electrical activity of the bowelInitiated in the interstitial cells of Cajal (ICC) (pacemaker cell),Santiago Ramon Y Cajal,He and Camillo Golgi received the Nobel Prize in 1906 for introduction of t
5、he silver-chromate stain,Slow wave (basic electrical rhythm)Intensity: 1015 mVFrequency: 312 cpmIonic mechanismspontaneous rhythmic changes in Na+-K+ pump activity,Normal BER frequencies in the gastrointestinal system,Spike potential (Action potential)Duration: 1020 msIonic mechanism:Depolarization:
6、 Ca2+ influxRepolarization: K+ efflux,The digestion and absorption,CarbohydrateAbout 250-300g/day:,Plant polysaccharides starch (2/3), Disaccharides: sucrose, lactose (1/3),Cellulose (fiber),Large intestine,Bacteria,Mouth(5%) + Small intestine (95%),Amylase Brush border enzymes,Proteins,Proteins,Fat
7、,Fat,Neural control of gastrointestinal function,Enteric nervous system (intrinsic)Autonomic nervous system (extrinsic),Enteric (Intrinsic) nervous systemMyenteric plexus (Auerbachs plexus)Submucosal plexus (Meissners plexus)Neurotransmitters secreted by enteric neuronsAch, NE, ATP, serotonin, dopam
8、ine, cholecystokinin, substance P, vasoactive intestinal polypeptide, somatostatin, leu-enkephalin, met-enkephalin, bombesin, etc.,Sympathetic nerveNEInhibitory (-),Autonomic nervous system,Parasympathetic nerveMainly AChStimulatory (+),Afferent sensory nerve fiber from the gutSensory fibers with th
9、eir cell bodies in the ENS terminate in the ENSSensory fibers with their cell bodies in the ENS send axons upward through the ANS to terminate in the prevertebral sympathetic gangliaSensory fibers with their cell bodies in the dorsal root ganglia or in the cranial nerve ganglia send axons to multipl
10、e area of the spinal cord or brain stem,Gastrointestinal reflexesThree typesReflexes that are integrated entirely within the enteric nervous systemReflexes from the gut to the prevertebral sympathetic ganglia and then back to the gastrointestinal tractReflexes from the gut to the spinal cord or brai
11、n stem and then back to the gastrointestinal tract,Gastrointestinal hormones,The hormones synthesized by a large number of endocrine cells within the gastrointestinal tractPhysiological functionsControl of the digestive functionControl of the release of other hormonesTrophic action,Gastrointestinal
12、hormones,Four main typesGastrinSecretinCholecystokinin (CCK)Gastric inhibitory peptide (GIP),Digestion in the stomach,The swallowing reflex is coordinated by the medulla oblongata, which stimulates the appropriate sequence of contraction and relaxation in the participating skeletal muscle, sphincters, and smooth muscle groups.,The coordinated sequence of contraction and relaxation in the upper esophageal sphincter, the esophagus, and the lower esophageal sphincter is necessary to deliver swallowed food to the stomach.,End.,
