Term
| Two types of nutrient sensing, hormone releasing cells |
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Definition
Closed system: senses nutrients on the basolateral side (nutrients pass through the epithelial cells)
Open system: senses nutrients on the luminal side of the epithelial cell |
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Term
| Two types of cell-membrane-bound hormone receptors |
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Definition
G-protein coupled
single trans-membrane domain |
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Term
| Three ways of regulating number of hormone receptors |
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Definition
Internalization: receptor invaginates into the membrane, forming a vesicle
Degradation: after receptor is in a vesicle, it fuses with another vesicle with enzymes for breakdown
Recycling: the process of invagination of receptors is reversed to get the receptor back into action. This is a much faster process than synthesizing new receptors. |
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Term
| Five major classic GI tract hormones |
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Definition
secretin
gastrin
cholecystokinin
GIP
motilin |
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Term
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Definition
Increases HCO3- secretion by pancreas.
Increases bile secretion from gall bladder.
Promotes pancreatic growth (maintenance).
Decreases H+ secretion in stomach (this occurs in dogs; there's no evidence of it occurring in humans).
Minor effect: Decreases gastric emptying. |
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Term
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Definition
Secretin is secreted by the S-cells of the duodenum and proximal jejunum.
It is stimulated by acid in the duodenum and consumption of alcohol or spicy food. |
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Term
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Definition
Gastrin major effects:
Increases acid secretion
Promotes stomach growth (maintenance).
Minor effects are:
an increase in pancreatic secretion of HCO3- and enzymes.
Increase bile production, especially HCO3-. |
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Term
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Definition
Gastrin is produced by the G-cells in the antrum of the stomach and duodenum.
Secretion is stimulated by distension of the stomach and presence of aromatic amino acids (from the protein in a meal).
Secretion is inhibited by a high level of acid. |
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Term
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Definition
CCK effects:
Contracts gall bladder (causing expulsion of contents into duodenum).
Increases production of pancreatic enzymes (HCO3-, enzymes).
Stimulates pancreatic growth (maintenance).
Inhibits gastric emptying. |
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Term
| Cholecystokinin secretion |
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Definition
CCK secretion stimulated by:
Fat component of meal: FFA
Protein components:
a) small peptides (less than or equal to 10 AA).
b) aromatic amino acids
No effect from carbs. |
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Term
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Definition
GIP (glucose-dependent insulotropic peptide) effects:
Promotes insulin production.
Minor: decreases fat absorption and liver glucose output.
Inhibits gastric secretion (non-physiologic). |
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Term
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Definition
GIP is produced by the K-cells in the duodenum and jejunum.
Secretion is stimulated by:
A meal with fat as a major component.
Carbs and proteins have less effect. |
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Term
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Definition
Motilin effects:
Major: increases GI tract mobility (throughout).
Induces MMC (migrating motor complex). |
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Term
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Definition
Motilin is secreated by the M-cells in the duodenum and jejunum.
Secretion is stimulated by fasting. |
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Term
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Definition
| migrating motor complex: waves of activity that sweep through the intestines in a regular cycle during fasting state. This facilitates transportation of indigestible substances through the GI tract into the colon. |
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Term
| peptides of GI tract with hormonal effects |
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Definition
Peptide YY : inhibits GI tract motility ('ileal brake')
gastric somatostatin : inhibits gastrin
gastric histamine : stimulates G-cells to secrete gastrin |
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