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Mac 4
Gastric Phase- Part B: Emptying and Pancreatic Secretion
37
Physiology
Undergraduate 2
04/10/2012

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