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Phys4 GI Lect3
Phys4 Hormonal control of the GI tract
| Question | Answer |
|---|---|
| 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
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