GI function Flashcards
What percentage of drugs are given by the oral route?
80%
What is the second deadliest cancer in the US?
colorectal cancer
The GI tract starts at the ______ and ends at the _____
mouth and anus
What are three GI tract accessory organs?
liver, gallbladder pancreas
What are the five layers of the GI wall?
serosa, muscularis, submucosa, mucosa, epithelial lining
The muscularis layer includes _______ muscle that traverses the length of the GI tract and ______ muscle that exists in localized rings.
longitudinal and circular
In what GI wall layer is the myenteric nerve plexus located?
muscularis (between longitudinal and circular layers)
Which GI wall layer has contact with the contents of the lumen?
epithelial lining
In what GI wall layer is the submucosal plexus located?
submucosa
What is mesentary?
helps attach the GI tract to the inside cavity
Which GI wall layer has many fold and contains glands and microvilli?
mucosa
A _________ is a fusion of fiber bundles partly separated by loose connective tissue that functions as a unit (usually).
syncytium
What are tonic contractions?
when the muscle stays contracted for a long time
With slow waves of depolarization, does a muscle contraction usually occur? Why or why not?
No, because there isn’t a great enough change in membrane potential for contractions
What is the purpose of a migrating motor complex (MMC)?
to facilitate emptying of GI contents
Tonic contractions can be caused by prolonged exposure to ________
calcium
Which kind of potentials usually lead to contractions of muscle?
spike potentials
What is the only place in the GI tract where slow depolarization waves result in muscle contractions?
stomach
Is the fixed frequency of slow waves of depolarization the same everywhere in the GI tract?
no
Voltage-dependent _______-______ channels exist in the smooth muscle.
calcium, sodium
Entry of _____ causes contraction
calcium
What are three things that stimulate depolarization (action potential beginning)?
stretching of muscle, stimulation by acetylcholine (parasympathetic nerves), stimulation by gastrointestinal hormones
What is one thing that stimulates hyperpolarization?
stimulation of fiber membranes by norepinephrine/epinephrine
What are three causes of tonic contractions?
continuous, repetitive spike potentials, hormones/factors that result in partial depolarization (but not action potentials), continuous entry of calcium into the cell
Is the Migrating Motor Complex (MMC) during fasted or fed conditions?
fasting
Which two plexuses are part of the enteric nervous system?
myenteric (auerbach’s), submucosal (meissner’s)
What does the submucosal plexus control?
movement of mucosal folds, glands/epithelial cells, local blood flow (concerned with local movement)
The ________ plexus has neurons that extend the entire length of the GI tract, while the _______ plexus has neurons within segments of the GI tract for local control.
myenteric and submucosal
What two things does the myenteric plexus stimulate?
increased tonic contractions, increased intensity/rate of rhythmical contractions
What does the myenteric plexus inhibit?
pyloric sphincter (stomach to duodenum, prevents acidic material from spilling out), sphincter of ileocecal valve (small intestine-ileum to cecum, prevents backflow in intestines)
What are three things that stimulate sensory afferent neurons (carry info to CNS)?
distention of gut wall, irritation of gut wall (nonspecific), specific chemical stimuli
The sympathetic GI innervation is mainly ____ganglionic, while the parasympathetic GI innervation is mainly ____ganglionic.
post and pre
The ________ innervation is mainly concerned with inhibition in the GI tract; what chemicals are used in inhibition?
sympathetic, norepinephrine, epinephrine
The ______ innervation is mainly concerned with stimulation in the GI tract; what chemical is used in stimulation?
parasympathetic, acetylcholine
What are the two types of functional movement in the GI tract?
propulsive, mixing movements
What is the Law of the Gut?
propulsive movements move food away from mouth (except with vomiting)
Which plexus is required for peristalsis?
myenteric
_________ GI reflexes involve more than 1 segment in the GI tract (ex.: gastrocolic involves stomach and colon).
long loop
What are the two types of GI reflexes?
local, long loop
Pain reflexes result in overall ________ of the GI tract.
inhibition
What are three processes that local GI reflexes can affect (increase or decrease)?
secretion, peristalsis, mixing movements
Which has a longer lasting effect: neurotransmitters or GI hormones?
GI hormones
What are five GI hormones?
secretin, gastrin, cholecystokinin (CCK), gastric inhibitory peptide (GIP), motilin
When and where is gastrin released?
in response to a meal (when), from G cells in stomach, duodenum, and jejunum (where)
What are some things that stimulate the release of gastrin?
protein digestion products, distention, gastrin releasing peptide
What are the physiological effects of gastrin?
increased acid secretion, increased growth of the mucosa
What inhibits gastrin secretion?
acidification of the stomach
Where is cholecystokinin (CCK) released from?
I cells in duodenum/jejunum
What are three things that stimulate release of CCK?
digestive products of fat (fatty acids or monoglycerides), peptides and single amino acids, weak acid in the intestine
The presence of _______ does NOT stimulate release of CCK.
triglycerides
What are the physiological effects of CCK?
emptying gallbladder (contracts gallbladder, relaxes sphincter of Oddi), stimulates pancreatic enzyme secretion, stimulates pancreatic bicarbonate secretion (weakly), inhibits gastric emptying, inhibits appetite, increases grow of pancreas/gallbladder mucosa
Once the ___________ is open, the gallbladder can empty.
sphincter of Oddi
Where is secretin release from?
S cells of duodenum/jejunum/ileum mucosa
What stimulates the release of secretin?
acid in duodenum, fatty acids in duodenum
What are the physiological effects of secretin?
inhibits gastric acid secretion, stimulates pancreatic and bile bicarbonate secretion, stimulates pepsin secretion in stomach
Where is gastric inhibitory peptide released from?
duodenum, proximal jejunum
What are the physiological effects of gastic inhibitory peptide?
stimulates insulin release, inhibits gastric acid secretion
When and where is motilin released?
during fasting, from duodenum, proximal jejunum
What is the physiological effect of motilin?
stimulates upper GI motility (migratin motor complex)
