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Phys4 GI Lect3

Phys4 Hormonal control of the GI tract

QuestionAnswer
Different types of Cell signaling seen in the GI 1.Cell-Cell (via gap junctions). 2.Autocrine. 3.Paracrine. 4.Neuronal (Synapse). 5.Endocrine via hemacrine (Blood). 6.Neuroendocrine (nerve synapses into BL stream). **2&3 move only in extracellular space
Through what does a paracrine & autocrine hormone travel through to reach its target? Extracellular space. NOT the blood stream.
What determines if a circulating endocrine hormone activates a particular cell? RECEPTOR SPECIFICITY
5 Major GI hormones 1.Gastrin. 2.CCK. 3.Secretin. 4.GIP. 5.Motilin.
Gastrin 1.Located:G-cells Antrum>Duo. 2.What triggers release: Vagas N, Protein, Distention. 3.Target: Stim (Parietal, ECL, Cheif cells). 4.Effects: Inc Pepsinogen, gastric acid, & histamine
CCK 1.Located:I-cells Duo=Jej>Ileum. 2.What triggers release: Protein, Fat. 3.Target: Stim (GB, Pancreatic ancinar cels). 4.Effects: Inc bicarb from GB & Pancreas, Inc bile & digestive enzymes (all kinds), Dec gastric acid & emptying.
Secretin 1.Located:S-cells Duo. 2.What triggers release: acid (pH<4.5), FA. 3.Target: Stim (liver, Pancreas), Inh (G & Parietal cells). 4.Effects: liver/Pancreatic bicarb into stomach, Dec gasrtic acid secretion. **Natural anti-acid
GIP 1.Located:K-cells in Duo=Jej. 2.What triggers release: Carbs (glucose), protein, fat. 3.Target: Inhib (G & Parietal cells), Stim (pancreas) 4.Effects:Dec acid secretion, Inc Insulin secretion. **Potent releaser of Insulin
Motilin 1.Located:Duo=Jej. 2.What triggers release: every 90min during fasting. 3.Target: GI musculature 4.Effects: Inc gastric & intestinal motility.
What is the only hormone originating/located in the Antrum? Gastrin
What is the most powerful releaser (trigger) of CCK Fat
What inhibits the release of Gastrin? Acid.
What inhibits the release of Motilin? A mixed meal (porteins, carbs, Fats)
Trophic effect of Gastrin Causes growth and enlargement of parietal & ECL cells as well as stimulates secretion. **Amplifies tumor in Zolinger-Elison disease (Gastrinoma of the Pancreas).
Trophic effect of CCK causes growth and enlargment of Pancreatic ancinar cells (exocrine pancreas).
What 3 things stimulate Parietal cells? 1.ACh. 2.Gastrin. 3.Histamine (released from ECL, enhances the effects of 1 & 2).
Pancreatic somatostatin 1.Loaction: D-cells Pancreas, gastric mucosa, duo. 2.What triggers it: Acid & Gastrin. 3.Target: Inh (G, Chief, Parietal, and ECL cells). 4.Effect: Dec gastric acid secretion.
Can pepsin be released in response to Secretin? YES, but usually not at physiological levels.
3 important Neurocrines (located in nerves, released into BL to affect distant target). 1.VIP. 2.GRP. 3.Enkephalins (opiates). 4.Neurotensin.
What nerves release GRP? Post-synaptic Enteric nerves (stimulated by PNS). **Causes Inc Gastrin Secretion via G-cell stimulation.
What common disorder are Enkephalins (opiates) useful in treating? Diarrhea
Actions of VIP 1.STIMULATORY: Pancreatic & intestinal secretion. 2.INHIBITORY: Gastric secretions, relaxes GI smooth muscle. **Increased by distention & vagal stimulation.
Actions of Enkephalins 1.Dec motility. 2.Dec intestinal secretions
2 Important Paracrines 1.Somatostatin (Delta-cells). 2.Histamine (ECL cells).
Candidate hormones 1.Pancreatic Polypeptide (Fat, protein, glucose). 2.Peptide YY (fat). 3.Enteroglucagons (hexose, fat).
Enteroglucagons **GLP-1** Potent insulin releaser, plays a role in ILEAL BRAKE
Created by: WeeG