gi hormone sheet

7/26/2019 GI Hormone Sheet

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1. CCKa. Source

i. I cells of duodenumb. Stimulated by

i. Peptides

1. CCK-RPa. In response to amino acids and fatty acids2. Monitor peptide

a. From acinar cells that are neurally regulatedii. Amino acidsiii.Fatty acids

c. Actionsi. Stomach

1. Inhibits gastric emptyinga. Negative feedback mechanism

2. Inhibits HCl secretion

ii. Bile ducts of liver1. Potentiates effect of secretin

iii.Gall bladder1. Binds to CCK-A2. Stimulates contractions

iv.Pancreas1. Binds to CCK-A receptors on basolateral membranes of acinar cells which

stimulates phosphorylation via Ca2+ pathwayv. Sphincter of Oddi

1. Stimulates relaxationvi.Large intestine

1. Stimulates segmentation and mass peristalsisvii.Splanchnic circulation

1. Vasodilationd. Receptors

i. CCK-A - requires sulfated tyrosine at position 7 of C-terminusii. CCK-B - requires aminated C-terminus

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2. Secretina. Source

i. S cells of duodenumb. Stimulated by

i. pH less than 4.5 in duodenum

c. Actionsi. Potent stimulator of water and HCO3 secretionii. Stomach

1. Inhibits gastric emptying2. Inhibits HCl secretion3. Inhibits secretion of gastrin4. Stimulates secretion of SST

iii.Bile ducts of liver1. Secretion of water and HCO3-2. CCK potentiates this

iv.Pancreas

1. Acinar cellsa. Phosphorylates CFTR via cAMP

i. Increases secretion1. Causes Cl to leave2. Water and Na follow

v. Splanchnic circulation1. Vasodilation

3. Gastrina. Source

i. G cells of stomachb. Stimulated by

i. Small peptidesii. Amino acidsiii.Gastric distentioniv.Vagal stimulation


1. Parietal cellsa. Binds to CCK-Bb. Secreted in response to GRP, ACh, and amino acids

d. Receptorsi. CCK-A - requires sulfated tyrosine at position 7 of C-terminus

ii. CCK-B - requires aminated C-terminus

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4. Histaminea. Source

i. ECL cellsb. Stimulated by

i. GABA

c. Actionsi. Acts as a paracrine moleculeii. Stomach

1. Stimulates HCl secretion by binding to H2 receptors on parietal cell andinitiating cAMP pathway

5. Somatostatina. Source

i. D cellsb. Modulation

i. Stimulated by low pHii. Stimulated by GLP-1 (glucagon-like peptides)

1. From intestinal L cellsiii.By GABAiv.Inhibited by Helicobacter pylori


1. Inhibits HCL secretiona. Paracrine mechanismb. Blocks histamine release by ECL cells

6. Aldosteronea. Increases Na-K exchangeb. Increases ENaC

7. Prostaglandinsa. Actions

i. Inhibit release of HCl by blocking histamine release

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8. Vagus nerve (vago-vagal reflex)a. Stimulated by

i. Gastric distentionb. Actions

i. Esophagus

1. Excitatory fibers releases ACh that binds to M3 receptorsa. Causes smooth muscle contractionb. Causes increased LES pressure

2. Inhibitory fibers release non-adrenergic, non-cholinergic (NANC)neurotransmitters

3. ***Figure 1-4ii. Stomach

1. Relaxation via vago-vagal reflexa. Occurs with swallowing

2. Accomodationa. Prevents increased intragastric pressure with stomach filling

i. Compliance, dependent on vago-vagal reflex3. Stimulates acid secretion via ACh

a. Stimulates parietals cellsb. Stimulates ECL cellsc. Stimulates release of GRPd. Inhibits D cells

iii.Pancreas1. Stimulates secretions via ACh

iv.Gallbladder1. Minor stimulation of contraction via ACh

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9. Acetylcholinea. Mouth

i. Stimulates salivary secretionsb. Smooth muscle

i. Stimulates contractions by binding to muscarinic receptors

c. Esophagusi. Increase LES pressure by binding to M3 receptor1. ACh can be released by

a. Vagal excitatory fibersb. Norepinephrine binding to !-receptors

d. Stomachi. Stimulate release of acid

1. By directly acting on the parietal cella. Ca2+ pathway

2. By stimulating gastrin release by G-cellsa. Ca2+ pathway

3. By stimulating histamine release from ECL cellsa. cAMP pathway

ii. Present in Cephalic and Gastric phase of acid secretione. Pancreas

i. Stimulates secretion by binding to acinar cellsii. Released in the intestinal phase of the fed period

f. Gallbladderi. Stimulates contraction

10.Sympathetic stimulationa. Mouth

i. Increases flow of saliva

b. Esophagusi. Increases LES pressure by binding to !-receptors

c. Stomachi. Inhibits gastric emptying

d. Activates myoepithelial cellse. Vasoconstriction

GI Hormone sheet

gi hormone sheet

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