Please enable JavaScript.

Coggle requires JavaScript to display documents.

GI Innervation (general regulatory mechansims (Autonomous contraction of…

- - - - secretin
      - CCK
      - GIP
      - gastrin
    - - somatostatin
      - histamine
  - - - present in submucosa of SI & LI
      - fxns
        
        GI secretions/absorptions
        
        local blood flow
        
        local contraction of submucosal m. >> infolding of GI mucosa
        
        secretion regulation
      - aka " Meissner's plexus"
    - - muscularis externa b/w inner circular & outer longitudinal layers
      - fxns:
        
        stimulatory
        
        inc. intensity of rhythmical contractions
        
        slightly inc. rate of rhythm of contraction
        
        inc. velocity of conduction of excitatory waves >> more rapid peristalsis
        
        inc. tonic contraction (tone) of gut wall
        
        inhibitory
        
        endings secrete inhibitory transmitter (possibly VIP)
        
        inhibits some GI sphincters (pyloric, ileocecal valve)
        
        motility regulation
      - aka "Auerbach's plexus"
      - consists mostly of linear chain of many interconnecting neurons
      - extends entire length of GI tract; located in all GI organs
    - - can act independent of extrinsic, but is usually modified by extrinsics
      - coordinates local reflexes (motility & secretions)
      - entirely w/in wall of gut (esophagus >> anus)
      - ~100 million neurons (= to spinal cord)
      - types of NTs:
        
        ACh (+), NE (-)
        
        ATP (-)
        
        serotonin (+), dopamine
        
        CCK
        
        VIP (-), GRP (+),
        enkephalins (+), substance P (+)
        
        somatostatin (-)
      - division of autonomic NS
      - coordinates & relays parasympathetic & sympathetic inputs to GI tract
  - - - fxns
        
        (-) GI smooth m. contraction
        
        (-) motility & secretions
        
        (+) mucosal m. contraction
        
        (-) digestion & absorption
        
        (+) sphincter constriction
      - preganglionic:
        
        cholinergic (ACh)
        
        most enter sympathetic chains >> ganglia (celiac & mesenterics)
        
        cell bodies in spinal cord
      - postganglionic:
        
        adrenergic (NE & small amounts of epi)
        
        bodies in ganglia
        
        fibers spread via postganglionic symp. nn. to all parts of gut
        
        some direct sympathetic supply to blood vessels, glands & smooth m.
      - origin: CNS >> T5-L2
      - postganglionics mainly synapse on myenteric & submucosal plexuses >> dec. activity of entire enteric NS
    - - pre- & post-ganglionic:
        
        cholinergic (ACh)
      - fxns
        
        (+) digestion & absorption
        
        (+) motility & secretions
      - named branches
        
        cranial
        
        almost entirely in vagus nn.
        
        except for few fibers to mouth & pharyngeal regions
        
        extensive innervation to esophagus, stomach & pancreas
        
        somewhat less innervation to SI to first half of LI
        
        sacral
        
        origin: S2, S3, S4 via pelvic nn.
        
        innervation to distal half of LI to anterorectal region
        
        sigmoidal, rectal & anal regions
        better supplied w/ parasym. than other GI areas
        
        execute defecation feflexes
      - postganglionics mainly synapse on myenteric & submucosal plexuses >> inc. activity of entire enteric NS
      - absence: dec. ACh, dry mouth, urine retention, constipation
    - - connect myenteric & submucosal plexuses
      - can greatly enhance/inhibit GI fxns in different regions by modulating enteric NS
- - - - defecation reflexes: colon & rectum >> spinal cord >> back again >> powerful colonic, rectal & abdominal contractions
      - pain reflexes: general (-) of entire GI tract
  - - - enterogastric reflexes: LI & SI >> (-) stomach motility & secretion
      - colonoileal reflex: colon >> (-) ileal emptying
      - gastrocolic reflex: stomach >> (+) colon emptying