Table__GI_Motility - Table GI Motility Saturday 7:50 PM...

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Neural Innervation and Hormonal Control of the GI Tract Location: upper 1/3 of esophagus a. CNX somatic motor neuron i. ACh --> Nm in striated muscles ii. Nucleus ambiguous b. Sensory nerves in submucosal plexus--> vagus --> NTSs i. Nucleus of the Solitary Tract (NTS) c. Striated Skeletal Muscle 1) Location: remainder of GI tract a. Smooth Muscle 2) Table - GI Motility Saturday, December 04, 2010 7:50 PM Gastrointestinal Page 1
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NTS--> CNX vagus--> submucosal plexus b. Can bypass CNS i. ENS (enteric neurons) c. In smooth muscle layer as network around cells i. Important for regulating electric potential of muscle cells ii. ICC (interstitial cells of Cajal) d. DVC--> Vagus --> myenteric plexus (location of parasympathetic ganglion) a. Also release Substance P for muscle contraction 1) Stimulatory= motor neurons--> ACh to M3--> contraction i. Relaxation of smooth muscle 1) Inhibitory= motor neurons--> iNANC release NO/VIP --> receptor Nn ii. Innervation of ENS plexuses b. Parasympathetic 3) Sympathetic ganglions near vertebrate (pre or paravertebral ganglia) a. (indirect effect) Ends of parasympathetic stimulatory nerves where NE binds presynaptic neuron to inhibit ACh release i. (direct effect) Circular muscle and release NE --> smooth muscle relaxation ii. Postganglionic nerves terminate at. .. b. Sympathetic 4) Respond to stretch i. Myenteric plexus--> vagus--> brain stem (DVC) ii. Vasovagal (afferent + efferent along CNX) iii. Make note that extrinsic neurons innervate plexuses iv. Extrinsic sensory neurons a. Short reflex that bypasses CNS i. Respond to stretch or luminal contents ii. Innervate other Ens, motor neurons, effectors iii. Enteric neurons system b. Sensory innervation 5) Tone maintained without relaxation i. LES, ileocecal valve, internal and external spincter ii. Continuous contraction state 1) Low level activation of Ca+ channels 2) Membrane potentials constantly depolarized iii. Tonic contraction
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Table__GI_Motility - Table GI Motility Saturday 7:50 PM...

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