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MEDICAL PHYSIOLOGY - PART 7

Sóng điện chậm trong ruột non. A, Không có tiềm năng hành động xuất hiện ở đỉnh của các sóng chậm, và các cơn co thắt cơ liên quan với mỗi sóng chậm là nhỏ. B, cơ tiềm năng hành động xuất hiện như là độ võng upwarddownward sắc nét ở các đỉnh của các sóng chậm. | CHAPTER 26 Neurogastroenterology and Gastrointestinal Motility 453 Small I 10 sec I WVWWM 10 g 1.2 mV FIGURE 26.4 Electrical slow waves Small 10 g in the small intestine. A No action potentials appear at the crests of the slow waves and the muscle contractions associated with each slow wave are U ẤẤẮẤẠA 1.2 mV small. B Muscle action potentials appear as sharp upward-downward deflections at the crests of the slow waves. Large-amplitude muscle contractions are associated with each slow wave when action potentials are present. Electrical slow waves trigger action potentials and action potentials trigger contractions. thetic signals to the digestive tract originate at levels 3 and 4 central sympathetic and parasympathetic centers in the medulla oblongata and represent the final common pathways for the outflow of information from the brain to the gut. Level 5 includes higher brain centers that provide input for integrative functions at levels 3 and 4. Autonomic signals to the gut are carried from the brain and spinal cord by sympathetic and parasympathetic nervous pathways that represent the extrinsic component of innervation. Neurons of the enteric division form the local intramural control networks that make up the intrinsic component of the autonomic innervation. The parasympathetic and sympathetic subdivisions are identified by the positions of the ganglia containing the cell bodies of the postganglionic neurons and by the point of outflow from the CNS. Comprehensive autonomic innervation of the di gestive tract consists of interconnections between the brain the spinal cord and the ENS. Autonomic Parasympathetic Neurons Project to the Gut From the Medulla Oblongata and Sacral Spinal Cord The origins of parasympathetic nerves to the gut are located in both the brainstem and sacral region of the spinal cord Fig. 26.7 . Projections to the digestive tract from these regions of the CNS are preganglionic efferents. Neu- Higher brain centers Interstitial cells of Cajal. .