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GI (physio)
Innervation, Hormones, NTs
40
Physiology
Graduate
02/22/2011

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Term
sympathetic innervation
Definition
-Inhibits GI secretions and motility (decreases gastric emptying)and Constricts blood vessels.
-ADRENERGIC post-ganglionic fibers (epi/NE)
Term
parasympathetic innervation
Definition
-Stimulates motor and secretory activity
-CHOLINERGIC post-ganglionic fibers (Ach, VIP)
Term
intrinsic innervation
Definition
-Can direct all functions of GI tract even w.o extrinsic innervation
-ganglia get input from extrinsic innervation and chemo/mechano receptors in mucosa.
Term
Myenteric Plexus
Definition
-exherts control over MOTILITY
-aka AUERBACHS plexus
Term
submucosal plexus
Definition
-controls SECRETION, regulates GI blood flow and senses environment in lumen
-aka MEISSNERS plexus
Term
ACh
Definition
-PSNS Cholinergic neuron
-contracts smooth muscle in GI, increases motility and strength of contractions
-behind bolus
Term
NE
Definition
-SNS Adrenergic nerve fibers
-relaxes smooth muscle
-ahead of bolus
Term
VIP
Definition
-PSNS: in mucosa and smooth muscle
-relaxes smooth muscle
-ahead of bolus
Term
Substance P
Definition
-cosecreted with ACh
-contracts smooth muscle of GI
-behind bolus
Term
Gastrin
Definition
-comes from G cells in stomach antrum
-stimulated for release by proteins/AA and distension
-Acts on parietal cells to increase secretions (promotes acidity! to begin digestion)
-enhances GI motility and relaxes iliocecal sphincter
-slows gastric emptying
Term
Secretin
Definition
-secreted by endocrine cells in duodenal mucosa in response to increased [H+] and fatty acids inside lumen (promotes secretion of bicarb from pancreatic duct)
-slows gastric emptying
-promotes bicarb/proenzyme secretion by Pancreas
Term
CCK
Definition
-secreted by endocrine cells in duodenal mucosa in response to FA, peptides and AA from a meal
-slows gastric emptying and secretion
-causes GB contraction and relaxes sphincter of Odi
-helps trigger satiety (fleeting fullness)
Term
GIP
Definition
-secreted by endocrine cells in duodenal mucosa in response to glucose and FA
-decreases glucose in blood, decreases motility and increases pH of stomach
-slows gastric emptying and secretion
-*stimulates insulin release
Term
Intestinal Cells of Cajal (ICC)
Definition
-generate slow waves
-abundant in Myenteric Plexus
-pacemaker for waves/AP/contractions
Term
salivary ducts
Definition
-modify salivary secretion by removing NaCl and adding a little K/Bicarb making it HYPOtonic
Term
neural control of salivary secretion
Definition
-PSNS increases volume of secretion by increasing IP3 and [Ca+]
-SNS increases enzymes in saliva and mucous by increasing cAMP
Term
Achalasia
Definition
-dz affecting LES by decreasing VIP/NO (inhibitory neurons) causing loss of peristalsis and increased tone
Term
unstirred layer
Definition
-formed by gastric epithelial cells secreting bicarb to neutralize acid trying to get into mucosa
Term
pepsin
Definition
-digests proteins in stomach
-must be secreted as pepsinogen (by chief cells) o/w would digest the body!
-pepsinogen secretion is stimulated by ACh/vagal activation during cephalic/gastric phase
Term
ACh/Gastrin/Histamine
Definition
-Increase HCl secretion by directly effecting parietal cells
-combo of these 3 augment each other
-POTENTIATION
Term
Somatostatin
Definition
-secreted by D-cells in antrum
-**physiological antagonist (anti) of HCl secretion
-suppresses Gastrin release from G- Cells and Histamine release from ECL cells
-lots of gastrin/H+ in lumen will trigger this hormone
Term
Zollinger-Ellison Syndrome
Definition
-caused by a gastrin secreting tumor leading to formation of a peptic ulcer (mucosal lesion of stomach or duodenum)
Term
retropulsion
Definition
velocity and force of contraction at pyloric sphincter can't get all food through at once, some is pushed back into stomach for more mixing/breaking down.
Term
Motilin
Definition
hormone initiating Migrating Motor Complex to clear lumen to prevent bacterial overgrowth of SI by microorg colonizing LI (every 90-120 min)
Term
gastroparesis
Definition
-delayed stomach emptying caused by a dysfunctional vagus nerve (decreased VIP)
-tx: prokinetics augment motility, erythromycin a motilin againist promotes peristalsis and domperidone
Term
Dumping syndrome
Definition
-results in incomplete digestion of proteins/fats, a decrease in pH and a decrease in digestive enzymes
-Sxs: steatorrhea, gas, cramps
Term
Proteases, pancreatic amylase and lipases
Definition
-digestive enzymes secreted by Pancreas and activated by enterokinase at side of digestion in duodenum
Term
Trypsin Inhibitor, mem bound enterokinase ans pro-enzyme form
Definition
protects pancreas from autodigestion
Term
CCK/Secretin/ACh
Definition
-stimulate pancreatic secretion
-two of them work together through cAMP and exhibit potentiation/amplification
Term
peptidases
Definition
-enzymes from pancreas break down proteins to oligopeptides then di/tri peptides in intestinal lumen
Term
pancreatic lipase
Definition
-converts triglycerides into monoglycerides and free fatty acids which then form micelles with help of bile salts
Term
chylomicron
Definition
-FFA and monoglycerides reform a triglyceride w/ help of watersoluble lipoproteins once inside enterocyte. This can then get exocytosed into lacteal.
Term
Grehlin
Definition
-Hunger hormone from ECC cells in stomach mucosa
-high before meals making you hungry
-high in fat ppl
-anorexics ignore it
Term
Glucagon Like Peptide GLP-1
Definition
-preproglucagon is cleaved in pancreas to glucagon and by intestinal L cells to this hormone
-the combo with PYY ‘really puts on the breaks’
-↑ insulin secretion afte a meal
-↓ food intake
-↓ SLOWS gastric emptying
-↓ glucagon secretion after a meal
Term
Peptide YY3-36
Definition
-comes from endocrine cells in SI/LI after a meal
-↑ EE
-↓ food intake
-↓ expression of Ghrelin
-↓ SLOWS gastric emptying
-Binds to Y2 receptor
Term
Neuropeptide Y
Definition
-very potent STIMULATOR of food intake and meal initiation
-rapid ↑ before meals (stays high as long as food is withheld)
-very high when body is stressed and/or fat stores are low so that u eat
Term
Agouti-Related Peptide (AgRP)
Definition
-Antagonist of α-MSH
-↑ Grehlin
-↓ leptin, insulin and PYY
-↑ in AgRP and NPY causes in ↑ in appetite!
-one of the most potent and long-lasting of appetite stimulators
Term
Leptin
Definition
-↓ food intake (anorexigenic)
-suppresses NPY and AgRP‘fat ppl should want to eat less’
-produced by AT in direct proportion to amount of fat
Term
increase appetite/food intake
Definition
Grehlin, NPY/AgRP
Term
decrease appetite and food intake
Definition
GLP/PYY, leptin
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