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GI Secretion
N/A
60
Physiology
Graduate
11/28/2011

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Term
What characterizes the cephalic phase of GI digestion?
Definition
Secretion in mouth due to conditional reflex (pavlov's reflex) or taste of actual food in mouth
Term
What characterizes the gastric phase of GI disgestion?
Definition
Food in the stomach
Term
What characterises the intestinal phase of GI digestion?
Definition
Food in the intestines
Term
What effect does parasympathetic stimulation have on the rate of GI secretion?
Definition
Increases GI secretion
Term
What effect does sympathetic stimulation have on GI secretion?
Definition
May slightly increase secretion, but may also counter parasympathetic stimulation and decrease secretion via vasoconstriction and reduction of blood supply
Term
What enzymes are found in saliva?
Definition
Ptyalin (alpha-amylase), lingual lipase, kallikrein
Term
What immunoglobulin is found in saliva?
Definition
IgA
Term
How does saliva compare osmotically to plasma?
Definition
Hypotonic
Term
What is the major neural stimulator of salivary secretion?
Definition
Parasympathetic NS, though Sympathetic NS contributes
Term
What effect does aldosterone have on salivary glands?
Definition
Increases K+ secretion, Na+ reabsorption
Term
What are the types of glands in the gastric mucosa of the stomach?
Definition
Oxyntic glands and Pyloric glands
Term
What types of cells make up oxyntic glands?
Definition
Parietal cells, Chief cells, Mucus cells
Term
What kind of cells make up pyloric glands?
Definition
Mucus cells, G cells
Term
What do parietal cells secrete?
Definition
HCL, intrinsic factor
Term
What do chief cells secrete?
Definition
Pepsinogen
Term
What do G cells secrete?
Definition
Gastrin
Term
What is the function of HCl in the GI tract?
Definition
Bactericidal, denatures polypeptides, fascilitates conversion of pepsinogen to pepsin
Term
What is the function of pepsin?
Definition
Initiates protein digestion
Term
What is the purpose of gastric lipase?
Definition
Fat digestion
Term
What is the function of mucus and HCO3?
Definition
Creates the gastric mucosal barrier which protects gastric mucosa, buffers gastric acid
Term
What is the function of intrinsic factor by parietal cells?
Definition
Vitamin B12 absorption
Term
What is the result of deficient levels of intrinsic factors?
Definition
Low vit B12 absorption leading to pernicious anemia
Term
What enzyme produces H+ and HCO3- in parietal cells?
Definition
Carbonic anhydrase
Term
What kind of transporter secretes H+
Definition
H+/K+ATPase proton pump
Term
What stimulates gastric acid secretion?
Definition
AcH, Histamine, Gastrin (stimulates histamine release)
Term
What specific receptor does ACh bind to on parietal cells?
Definition
M3
Term
What specific receptor does gastrin bind to on parietal cells?
Definition
CCKB
Term
What kind of signal transduction do ACh and Gastrin receptors participate in in parietal cells?
Definition
G-protein Gaq activated PLC -> PKC and the release of Ca2+
Term
What is the specific receptor on parietal cells for Histamines?
Definition
H2 producing cAMP and activating PKA
Term
Which inhibitors oppose the action of histamines on parietal cells?
Definition
Somatostatin and Prostaglandins
Term
What nerve directly stimulates parietal cells?
Definition
Vagus nerve via ACh
Term
Vagal stimulation of what enhances gastric acid secretion through what?
Definition
ECL cells via increased histamine release
Term
Vagal stimulation of what promotes gastric acid secretion by inhibiting the release of what?
Definition
D cells, inhibiting somatostatin release
Term
What stimulates D cells to release somatostatin? What kind of feedback is this?
Definition
Luminal H+, negative feedback
Term
What effect does food have on gastric pH?
Definition
Raises pH due to buffering effect
Term
When are gastric secretions at their highest?
Definition
1hr after a meal
Term
Chyme in the duodenum stimulates what?
Definition
Secretin release and enetrogastric reflex
Term
What is the function of secretin?
Definition
Inhibition of gastric acid secretion
Term
What is the function of the enetrogastric reflex
Definition
Inhibits gastric secretion and stomach emptying
Term
What stimulates gastric acid secretion in the stomach?
Definition
Wall distention, presence of digested protein fragments
Term
What is the major stimulus for gastric secretion in the intestines?
Definition
Circulating amino acids are the major stimulus, distention of the intestinal wall is minor stimulus
Term
What stimulates the secretion of pepsinogen?
Definition
ACh, H+ in the stomach lumen, Secretin, Gastrin
Term
What are the functions of the mucus secreted by surface cells in the gastric mucosa?
Definition
Diffusion barrier for H+ and pepsins, also traps HCO3- which titrates any H+ that diffuses into the gel layer from the stomach lumen
Term
What is the result of H+ penetrating the gastric mucosa into the gastric epithelium?
Definition
Damage to mast cells, releasing histamines that trigger an inflammatory response. May lead to injury/ulcers.
Term
What factors contribute to peptic ulcer disease?
Definition
H. Pylori, Aspirin, Bile acids
Term
What is the distribution of exocrine and endocrine cells in the pancreas?
Definition
90% exocrine, 10% endocrine
Term
What do ductal cells of the pancreas secrete and what are their functions?
Definition
Aqueous component that secretes HCO3-, H2O, and electrolytes, optimizes pH for digestive enzymes and prevents ulceration
Term

What do acinar cells of the pancreas secrete and what are their functions?

Definition
Enzymatic component, secretes digestive enzymes (amylase, lipase, proteases), aids digestion
Term
What hormones regulate pancreatic secretion?
Definition
Secretin and Cholecystokinin
Term
What stimulates secretin release?
Definition
Acidic chyme in the duodenum
Term
What is the primary effect of secretin?
Definition
Increases HCO3- from pancreatic ductal cells and liver
Term
What stimulates the release of Cholecystokinin?
Definition
Amino acids, fatty acids
Term
What is the primary effect of Cholecystokinin?
Definition
Increases digestive enzyme secretion
Term
What is the primary neural regulator of pancreatic secretions and what are the effects?
Definition
ACh, stimulated by peptides and amino acids, increases enzyme and aqueous secretions from the pancreas
Term
What type of secondary messengers do ACh and CCk use on pancreatic acinar cells?
Definition
Both utilize G-receptors -> PLC -> PKC and release of Ca2+
Term
What secondary messengers do VIP and Secretin activate?
Definition
Both use G-protein receptors -> Adenylyl Cyclase -> cAMP -> PKA
Term
What should be kept in mind about dosing patients with CCK?
Definition
High doses are less effective
Term
What electrolyte movement generates HCO3- cotransport?
Definition
Cl- movement out of the cell due to secretin causes favored Na/HCO3 cotransport
Term
What would be the effect of a high protein, low carb diet on pancreatic secretions?
Definition
Increased proportion of proteases, decreased amylase
Term
What is the effect of insulin on the pancreas?
Definition
Maintains normal rates of pancreatic protein synthesis and stores of digestive enzymes
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