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64 Cards in this Set

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______ innervates esophagus, stomach, pancreas, proximal section of large intestine
Vagus nerve
______ innervates last half of large intestine
Pelvic nerve
(innervates longitudinal and circular muscle layers and controls movement)
myenteric plexus
(innervates epithelium, endocrine cells and blood vessels and controls secretions)
submucous plexus
Smooth muscle electrical activity is the result of _________ changes
Slow resting membrane potential
Superimposed on basic rhythm
Depolarization: Ca++ influx
Repolarization: K++ efflux
Directly cause mm contraction
Spike potentials
when food enters stomach, stomach <-> brainstem circuit reduces stomach wall muscle tone
Vagovagal reflex
Pyloric muscle contracts with each peristaltic wave
retropulsion
prevents large food particles in chyme from exiting stomach
pyloric sphincter contraction
prevent excess gastric emptying
Duodenal enterogastric reflexes
released in response to fat in chyme -> slows emptying of stomach (feedback mechanism)
Mucosal jejunum CCK
Parietal cells secrete (2)
gastric acid, intrinsic factor
Effects of excess stomach acid (pH below 3)
Decreased G-cell gastrin secretion

inhibitory nervous reflex results in decreased secretions
Pyloric glands located in _____ secrete protective mucus, pepsinogen, gastrin
antrum
During gastric phase, _______ and hormone release decrease secretions
enterogastric reflex
ACID (HCl)secreted by _______
parietal cells
PEPSINOGEN Synthesized by ________
chief cells
Required for absorption of vitamin B12, secreted by parietal cells, combines w/Vit B12, then absorbed in ileum.
INTRINSIC FACTOR
Stimulates parietal cells and chief cells to secrete HCl and pepsinogen
GASTRIN
produced by antral G cells, stimulates gastric acid and pepsin secretion and mucosal growth
Gastrin:
contracts gallbladder and causes pancreas to secrete enymes, inhibits gastric emptying, stimulated by small peptides, amino acids, fatty acids in food
-CCK:
released by S cells in small intestine, causes watery alkaline pancreatic secretions
-Secretin:
produced by small intestine K cells, stimulates release of insulin
-GIP (glucose-dependent insulinotropic polypeptide):
causes release of water and electrolytes, relaxes smooth muscle
-VIP (vasoactive intestinal peptide):
inhibits food intake and gastric acid secretion, released by jejunum by fat
-Peptide YY:
secreted by stomach, increases food intake partly by action on hypothalamus
-Ghrelin:
produced in both stomach and intestines, contracts smooth muscle, role in MMCs
-Motilin:
released by D cells in GI tract and pancreas, inhibits motilin, gastrin, VIP, GIP, secretin release
-Somatostatin: -
released by ileum, inhibits motility, increases ilieal blood flow
Neurotensin:
increases small intestine motility
-Substance P:
neurotransmitter that increases gastrin secretions upon vagal stimulation
-GRP (gastrin-releasing peptide):
released by pancreas, important in carbohydrate metabolism
-Glucagon:
secreted by intestines, receptors are stimulated by some E coli toxins
-Guanylin:
in body of stomach parietal cells secrete
intrinsic factor
HCL
in body of stomach chief cells secrete
pepsinogen
antrum secretes
gastrin
total emptying of the stomach takes
5h
transit through colon takes
30-40h
breaks down carbohydrates
salivary amylase
breaks down PROTEIN and converts pepsinogen to the active enzyme pepsin
HCl
converts more precursors to active enzymes via autocatalysis
-an endopeptidase that splits peptide bonds involving aromatic L-amino acids
PEPSIN
Increase absorptive surface area of mucosa by 3X
Folds of Kerckring
1 mm projections increase
mucosa surface area 10X
Villi
Projections on villi form
brush border; increase surface area 20X
Microvilli
-diffuses across plasma membranes of epithelial cells
-absorbed to a greater extent in the small intestine
-fat-rich foods delay absorption
ALCOHOL
-weak acid (acetylsalicylic acid)
-does not dissociate in the gastric lumen
-absorbed similar to alcohol
ASPIRIN
-relatively rapid absorption
Caffeine
the primary stimulant of gastric emptying
VOLUME
FLUIDITY affects the rate of gastric emptying; the more fluid the _____ it emties
faster
most potent inhibitor of gastric emptying
FAT
other INHIBITORY DUODENAL INFLUENCES
Dietary ACID
HYPERTONICITY
DISTENTION
MECHANISM FOR INHIBITION (2)
ENTEROGASTRIC REFLEX
ENTEROGASTRONES
ENTEROGASTRONES
secretin
cholecystokinin (CCK)
gastric inhibitory peptide (GIP)
peptide YY
Pancreatic alpha-amylase (much more powerful than saliva alpha-amylase) digests nearly all remaining starches in ______ chyme
duodenal
____________ from microvilli brush border hydrolyzes disaccharides and small glucose polymers to monsaccharides
Intestinal epithelial enzymes
_________ rapidly digests triglycerides into
fatty acids and 2-monoglycerides
Pancreatic lipase (main enzyme)
Bile salts and fat assemble into ______ (central fat globule made up of
monoglycerides and fatty acids plus bile salt molecules extending outward)
micelles
Only fats absorbed in stomach are _________ ; the rest are absorbed in small intestine
short-chain fatty acids
protien digestion begins in the stomach when ______ secreted by chief cells begins to break down collagen
Pepsin
Proteolytic pancreatic enzymes that splits protein molecules into small polypeptides
Trypsin/ chymotrypsin
Proteolytic pancreatic enzyme that trims off polypeptide carboxyl end amino acids
Carboxypolypeptidase
Proteolytic pancreatic enzyme that digests meat elastin fibers
Proelastase -> elastase
Last step in protien digestion occurs __________--aminopolypeptidase and dipeptidases split large polypeptides into tripeptides, dipeptides and amino acids
brush border
Protien digestion: In _________, remaining tripeptides and dipeptides are reduced to amino acids which enter the circulation
enterocytes