Term
| What are the 4 aspects of gastric motility? |
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Definition
| Filling, storage, mixing, and emptying. |
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Term
| Where do storage, and mixing take place in the stomach? |
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Definition
Storage = Body
Mixing = Antrum |
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Term
| Where are the factors located that regulate emptying? |
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Definition
| They are mostly located in the duodenum |
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Term
| What cells are the "pacemakers of the gut"? |
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Definition
| The Interstitial Cells of Cajal (ICC) |
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Term
| What type of mechanism allows the ICC's to control firing? |
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Definition
| A slow-wave mechanism paired with L-type Ca++ currents to cause action potentials in the smooth muscle. |
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Term
| What is the relation between action potential firing rate and muscle contractions? |
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Definition
| Force and duration of muscle contraction is directly to amplitude and frequency of action potentials. |
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Term
| How does retropulsion work and how does it work?? |
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Definition
| The pyloric sphincter closes as the antrum contracts towards it. This build pressure in the antrum causing a jet-like propulsion of material into the body. |
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Term
| What are the three processes of food mixing in the antrum of the stomach? |
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Definition
| Propulsion, grinding, and retropulsion. |
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Term
| What is propulsion and how does it work? |
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Definition
| Propulsion is the initial movement of food in the antrum towards the pylorus. This occurs through a peristaltic wave started by the ICC. |
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Term
| What is grinding and how does it work? |
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Definition
| As the material in the antrum approaches the pylorus it begins to get churned by the continuing peristaltic wave. |
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Term
| What factor in the stomach affects gastric emptying? |
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Definition
| The amount of chyme regulates the strength of stomach contraction. |
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Term
| What factors in the duodenum affect gastric emptying? |
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Definition
Fat (more fat = less fat emptying)
Acid (unneutralized acid in duodenum delays emptying)
Hypertonicity (high osmolarity inhibits emptying)
Distention (too much chyme in duodenum = less emptying) |
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Term
| What factors outside the GI system affect gastric emptying? |
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Definition
Emotion (can stimulate or inhibit emptying)
Intense pain (increases symp. activity to inhibit emptying) |
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Term
| What is emptied faster a solutiong of 1% glucose, or a meal of cubed liver? |
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Definition
| The glucose solution is emptied much faster. |
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Term
| What does the lag phase of gastric emptying correspond to? |
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Definition
| The time needed to reduce the meal to particles less than 2mm in size. |
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Term
| What is emptied fastest, an oleate meal, an acid meal, or a saline meal? |
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Definition
| They are emptied in the reverse order. (saline meal, acid meal, oleate meal) |
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Term
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Definition
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Term
| What coordinates the vomiting reflex? |
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Definition
| The vomiting center in the medulla of the brain stem. |
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Term
| What causes the expulsion of stomach contents during vomiting? |
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Definition
| The diaphragm contracts downwards as the abdominal viscera contracts to increase intra-abdominal pressure. This squeezes the stomach from above and below to force the contents out. |
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Term
| What events other than contractile forces occur to facilitate vomiting? |
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Definition
| Both esophageal sphincters relax, the glottis closes, and the uvula raises to close off nasal cavity. |
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Term
| What factors can cause vomiting? |
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Definition
| Tactile stimulation of back of throat, irritation or distention of stomach, chemical factors effecting the chemoreceptors in the brain, and psychogenic factors such as nausea/anxiety. |
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Term
| What two tissue types exist in the pancreas? |
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Definition
| The pancreas contains both endocrine and exocrine tissues. |
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Term
| What pancreatic cells are responsible for its endocrine function? |
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Definition
| The islets of Langerhans secrete insulin and glucagon. |
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Term
| What pancreatic cells are responsible for its exocrine function? |
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Definition
Pancreatic acinar cells secrete the pancreatic enzymes.
Pancreatic duct cells secrete bicarbonate. |
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Term
| What two factors regulate pancreatic exocrine function? |
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Definition
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Term
| What three types of enzymes exist in pancreatic juices, and what do they do? |
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Definition
Proteolytic enzymes - digest proteins
Pancreatic amylase - Converts polysaccharides into the disaccharide amylase
Pancreatic lipase - Only enzyme secreted throughout entire digestive system that can digest fat |
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Term
| What three proteolytic enzymes make up the pancreatic proteolytic enzymes? |
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Definition
Trypsinogen - converted to active form trypsin
Chymotrypsinogen – converted to active form chymotrysin
Procarboxypeptidase – converted to active form carboxypeptidase |
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Term
| What converts pepsinogen into pepsin within the small intestine? |
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Definition
| Enteropeptidase within the brush border of the intestine. |
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Term
| What converts the inactive zymogens of the pancreas into their active forms? |
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Definition
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Term
| What happens to pancreatic secretion levels during a period of fasting? |
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Definition
| The juices are released in a rhythmic fashion. |
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Term
| What happens to pancreatic secretion levels during a fed state? |
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Definition
| The juices are released at much higher levels in spikes at a great frequency. |
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Term
| What two pathways in pancreatic acinar cells control enzyme release, and which plays the larger role? |
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Definition
| cAMP-depandent, and Ca++-dependent pathways. The Ca++ pathway is much more important. |
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Term
| What two signals stimulate the cAMP-dependent pathway in pancreatic acinar cells? |
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Definition
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Term
| What three signals stimulate the Ca++-dependent pathway in pancreatic acinar cells? |
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Definition
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Term
| What type of feedback occurs in the secretin pathway? |
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Definition
| A negative feedback system. |
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Term
| The presence of what in the duodenum is found to significantly increase the release of secretin? |
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Definition
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Term
| What do duodenal I cells secrete? |
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Definition
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