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GI Tract - self assessment questions back to the teaching materials

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NOTE: These questions have one and only one correct answer

Q1. In the enteric nervous system:

(a) excitatory motor neurons from myenteric ganglia release acetylcholine, substance P, vasoactive intestinal peptide, or nitric oxide (NO) onto smooth muscle cells of the circular and longitudinal layer.
(b) interneurons release substance P.
(c) many stimulatory secretomotor neurons from the submucosal plexus release NO onto gland cells in the gastrointestinal tract.
(d) vasodilator neurons may release norepinephrine onto mucosal blood vessels.
(e) numerous sensory neurones, whose cell bodies are in the myenteric and submucosal ganglia respond to mechanical and chemical stimuli.

   



Q2. In the esophasgus:

(a) the swallowing reflex is elicited when touch receptors on the posterior part of the hard palate are stimulated.
(b) the upper esophageal sphincter opens early on in the swallowing reflex and remains open for most of the time that the esophageal peristaltic wave travels from the upper to the lower end of the esophagus.
(c) if food remains in the esophagus after a swallow, a new complete swallowing reflex occurs.
(d) in achalasia, the lower part of the body of the esophagus contracts spasmodically.
(e) the lower esophageal sphincter remains open while the peristaltic wave traverses the length of the esophagus.

   



Q3. With regard to gastric emptying:

(a) fats tend to be emptied during the active contractile phase of the migrating myoelectric complex (MMC).
(b) acid in the duodenum elicits release of gastric inhibitory peptide, which slows the rate of gastric emptying.
(c) indigestible objects tend to be emptied into the duodenum during the active contraction phase of the MMC.
(d) fats and fat digestion products in the duodenum elicit the secretion of secretin, which slows the rate of gastric emptying.
(e) gastrin released from duodenal G cells in response to peptides and amino acids decreases the force of gastric contractions.

   



Q4. In the small intestine:

(a) peristalsis is the most frequent type of contractile behaviour in a fed individual.
(b) stimulating sympathetic nerves have very little effect of segmentation.
(c) in a fasted individual, segmental contractions are more or less continuous.
(d) the MMC is characterised by 75 or 90 minutes of quiescence, punctuated by 3- to 6- minute periods of intense and propulsive contractions.
(e) long-range peristalsis occurs frequently.

   



Q5. With regard to salivary secretion:

(a) the major control of salivary secretion is via the enteric nervous system
(b) secretory endpieces (acini) secrete a fluid that contains salivary amylase and has HCO3- at levels much higher than in plasma.
(c) when salivary secretion is stimulated under physiological conditions, the concentration of bicarbonate in saliva rises.
(d) stimulation of the sympathetic nerves to salivary glands results in prolonged stimulation of salivation.
(e) agonists that elevate cyclic AMP stimulate acinar cell secretion; agonists that elevate intracellular Ca++ inhibit secretion of fluid and amylase.

   



Q6. With regard to gastric secretions:

(a) oxyntic glands that contain parietal cells are located in the body and the pylorus of the stomach.
(b) the higher the flow rate of gastric juice, the higher is its Cl- concentration.
(c) patients with gastric ulcers secrete larger amounts of HCl than do normal individuals.
(d) glands in the pylorus contain G cells that secrete gastrin, cells that secrete mucus, and numerous chief cells and parietal cells.
(e) the rate of HCl secretion during the cephalic phase is low, but the total amount of HCI secreted may be large.

   



Q7. With regard to gastric acid secretion.

(a) the total amount of H+, K+-ATPase present in an unstimulated parietal cell is low.
(b) H+ is secreted across the basolateral membrane of the parietal cell by H+, K+-ATPase.
(c) HCO3- leaves the parietal cell at the basolateral membrane, and its downhill efflux powers the uphill entry of Cl- into the parietal cell.
(d) Cl- is secreted into the secretory canaliculus via a Cl- active transport protein.
(e) H2 receptor blockers inhibit HCl secretion by directly inhibiting the H+, K+-ATPase.

   



Q8. With regard to pancreatic secretion:

(a) the acinar cells and intralobular ducts secrete a fluid that contains the enzyme component and bicarbonate levels that are higher than in plasma.
(b) secretin stimulates the acinar cells and intralobular ducts to produce a secretion with a high bicarbonate concentration.
(c) during the gastric phase, CCK stimulates pancreatic acinar cells to secrete pancreatic enzymes.
(d) secretin does not influence the response of acinar dells to CCK.
(e) pancreatic acinar cells are stimulated to secrete by agonists that elevate intracellular cyclic AMP, but not by agonists that elevate intracellular Ca++.

   



Q9. With regard to the digestion and absorption of carbohydrates:

(a) the only monosaccharides absorbed to an appreciable extent are glucose and galactose.
(b) a-dextrinase (isomaltase) is the enzyme in the cytosol of jejunal epithelial cells that is responsible for cleaving the a-1,6-glycosidic linkage of branched starch molecules.
(c) certain disaccharides are taken up by intestinal epithelial cells.
(d) a small fraction of the world’s adult population is lactose intolerant.
(e) sucrase and isomaltase ( a-dextrinase) are synthesised as a single polypeptide chain.

   



Q10. With regard to the digestion and absorption of proteins:

(a) trypsinogen is activated by chymotrypsin that is secreted by the duodenal mucosa.
(b) oligopeptidases present in pancreatic juice cleave peptides to produce smaller peptides and single amino acids.
(c) neutral amino acids are transported across the brush border membrane by a single Na+-powered secondary active transport protein with broad specificity for neutral amino acids.
(d) dipeptides and tripeptides are taken up across the brush border membrane by a single type of H+-powered secondary active transport protein.
(e) dipeptides and tripeptides are transported across the basolateral membrane and appear in portal blood.

   



Q11. With regard to the intestinal handling of salts and water:

(a) the enteric nervous system plays a minor role in regulation of intestinal salt and water transport.
(b) aldosterone enhances the absorption of Na+ in the colon mainly by increasing the number of Na+, K+-ATPase molecules in the basolateral membrane.
(c) cells in the crypts of Lieberkühn are stimulated to secrete Cl- into the lumen by an agonist that elevates intracellular cyclic AMP in the crypt cells.
(d) the glucose that is present ion oral rehydration solution promotes the absorption of Na+, Cl-, and water by the cells in the crypts of Lieberkühn.
(e) in the jejunum and ileum, very little K+ is absorbed via the paracellular pathway

   



Q12. With regard to the intestinal absorption of iron:

(a) the fraction of the ingested inorangic iron that is absorbed is larger than the fraction of the ingested heme iron that is absorbed.
(b) vitamin C inhibits iron absorption by forming a complex with ferrous (Fe++) iron.
(c) iron bound to ferritin in intestinal epithelial cells is part of the absorbable pool of iron.
(d) Fe++, but not Fe+++, Is taken up across the brush border membrane by a specific transport protein.
(e) the intestinal epithelial cells of iron-deficient animals contain more apoferritin than do the intestinal epithelial cells of iron-replete individuals.

   





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Copyright © 1998 University of Bristol. All rights reserved.
Author: Phil Langton 		Last modified: 11 Jun 1999 07:25
Authored in CALnet