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102 Cards in this Set
- Front
- Back
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Innervation and regulation of GIT
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190
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Layers of intestines 8
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Epithelium, lamina propria, muscularis mucosa, submucosal plexus, circular muscle, myenteric plexus, longitudinal muscle, serosa
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contraction of muscularis mucosa causes
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change in surface area for secretion/absorption
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contraction of circular muscle causes
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dec in GIT diameter
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contraction of longitudinal muscle causes
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shortening of GIT segment
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Meissner's plexus is the same as
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submucosal plexus
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Auerbacch's plexus is the same as
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myenteric plexus
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PNS is carried via
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CN X and pelvic nerves
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SNS is carried via
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prevertebral -> myenteric & submucosal plexi
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Myenteric/Auerbach plexus controls
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GI motility
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Submucosal/Meissner plexus controls
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secretion & blood flow
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Gastrin is secreted by
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G cells of stomach
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3 stim of gastrin
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small peptides/amino acids, stomach distension, vagus
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2 inh of gastrin
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H+, somatostatin
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Axn of gastrin 2
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inc gastric H+, stim gastric mucosa growth
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CCK is secreted by
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I cells of duodenum/jejunum
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2 stim of CCK
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small peptides/amino acids, fatty acids
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Axn of CCK 5
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stim GB contraction, relax Sphincter of Oddi, inc panc enzyme, inc HCo3 secretion, inh gastric emptying
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Secretin secreted by
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S cells of duodenum
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2 stim of secretin
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H+ in duodenum, fatty acid in duodenum
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Axn of secretin 2
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inc HCO3 secretion, dec gastric H+ secretion
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GIP is secreted by
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duodenum/jejunum
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3 stim for GIP
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fatty acids, amino acids, oral glucose
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Axn of GIP 2
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inc insulin secretion, dec gastric H+ secretion
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most potent stim for gastrin of amino acids 2
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phe, trp
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somatostatin is secreted by
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Panc
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main stim for somatostatin
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H+ in GI lumen
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Axn of somatostatin 2
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inh all GI hormones, inh gastric H+ secretion
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histamine is secreted by
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mast cells fo gastric mucosa
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Axn of histamine 3
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inc gastric H+ secretion directly; potentiate gastrin fx; stim vagus
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VIP, GRP, enkephalins are secreted by
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GIT neurons
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Axn of VIP 3
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relax GI SM, stim HCO3 secretion, inh gastric H+ secretion
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Axn of GRP 1
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stim gastrin release from G cells (vagal route)
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Axn of enkephalins 2
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contract GI SM, inh intestinal secretion
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GI motility
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195
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GIT is mostly what type of SM
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unitary
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what part of GIT is not unitary SM?
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Sphincters
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phasic contractions occur in 3
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esophagus, gastric antrum, SI
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Tonic contractions occur in 4
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LES, orad stomach, ileocecal and internal anal sphincters
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characterisitcs of slow waves in GIT 3
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spontaneous; inherent to SM; not AP
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slow waves originate in
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interstitial cells of Cajal (GI pacemaker)
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slow wave freq are lowest in the? Highest in the?
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lowest in stomach, highest in duodenum
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role of chewing 3
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lubricate, mix, inc surface area
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sawllowing reflex is coordinated in
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medulla
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what prevents air form enter upper esophagus/gastric acid entering lower esophagus
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Sphincters
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intraesophageal pressure should be
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lower than atm
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primary v. secondary peristaltic contraction
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primary creates high pressure area to push; secondary clears remaining
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what nerve & NT is important to relaxing LES
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CN X, VIP
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3rd muscular layer of stomach
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oblique
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which is proximal: orad or caudad
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orad (toward the mouth)
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receptive relaxation is
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relaxing of orad stomach to allow food to enter
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receptive relaxation is mediated by
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CN X
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CCK fx on receptive relaxation
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enhances by inc orad distensibility
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if threshold is reached during slow waves in caudad
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AP fired -> contraction
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freq of slow waves sets the
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max freq of contractions
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closing of distal antrum when caudad contracts allows
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retropulsion and food mixing
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meigrating myoelectric complex occur at what intervals
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90 min
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mediator of the MMC
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motilin
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gastric emptying is fastest when stomach contents are
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isotonic
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segmentation contractions in SI causes what type of movement
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back & forth (mixing)
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2 parts of peristaltic contractions in SI
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contract behind bolus, relaxation in front
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gastroileal reflex
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food in stomach trigger inc peristalsis in ileum and ileocecal sphincter relaxation
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fecal material moves slower in prox or distal colon
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distal (less H2O)
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Rectosphincteric reflex
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fecal material in rectus contracts it & relaxes IAS
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gastrocolic reflex
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food in stomach inc colon motility & freq of BM
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3 parts to vomiting
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reverse peristalsis, closing of UES, high presure opening esophageal sphincter
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GI Secretion
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199
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5 characteristics of saliva
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high HCO3, high K, hypotonic, amylase, lingual lipase
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does the SNS stim or suppress saliva?
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STIMULATE
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3 components of gastric secretion
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HCl, pepsinogen, intrinsic factor
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5 characteristics of panc secretion
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high HCO3, isotonic, lipase, amylase, protease
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4 components of bile
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bile salts, bilirubin, phospholipids, cholesterol
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3 major glands making saliva
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parotid, submandibular, sublingual
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where is saliva made hypotonic?
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ducts not acinar
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what exchanges occur in the duct
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Na/K and Cl/HCO3 exchange (but resorption > secretion)
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what makes saliva more hypotonic? 2
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aldosterone, low flow rate
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what secretes pepsinogen?
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chief cells of the body of stomach
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what secretes HCl/intrinsic factor?
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parietal cells in the body of the stomach
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second messenger for Ach, gastrin on gastric parietal cell
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Gq
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second messenger for histamine
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Gs
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second messenger for somatostatin, PG?
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Gi
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HCO3/Cl exchange in the panc occurs where
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in ductal cells
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second messenger for secretin
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Gs
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second messenger for CCK
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Gq
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where are bile salts resorbed
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ileum
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glucose and galactose are aborbed by
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Na-dependent cotransport
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fructose is absorbed by
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facilitated diffusion
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endo v. exopeptidases
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exo work a terminus
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optimum pH for pepsin
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pH 1-3
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panc proteases - 5
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chymo/trypsin, elastase carboxypeptidase A/B
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which is the activating machine?
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trypsin
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what activates the activating machine?
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enterokinase (brush border enzyme)
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free amino acids are absorbed by
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Na-dependent cotransport
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di & tripeptides are absorbed by
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H+-dependent cotransport
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tight tight jxn are found in
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the colon
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leaky tight jxn are found in
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SI, gallbladder
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Na reabsorption in SI is mostly through
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cotransport
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Na reabsorption in colon is mostly through
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Na channels
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mech of diarrhea inc K secretion
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like in renal tubule, inc flow inc distal secretion
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secretory mechnism of electrolytes and H2O are located in
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crypts
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conjugation of bili occur in
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liver
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conversion of conj bili to urobilinogen and uro/stercobilin occurs in
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SI
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