Lecture 16 Flashcards
Compare propulsive movements of the GI tract with Mixing movements
Propulsive movements cause a contractile ring to move down the GI tract, are usually stimulated by distension, and can occur in any direction (usually they die out quickly if they are traveling in an oral direction
These move contents while mixing movements just contract and help breakup the bolus
Mixing movements may be caused by propulsive movements themselves and are local, intermittent constrictive contractions
For slow waves, describe their potentials, what those potentials are inherent to, and how they are spread. What important frequency do these type of waves set for each part of the GI tract?
Slow waves are NOT action potentials they are oscillating potentials inherent to smooth muscle itself and spread through gap junctions
These occur spontaneously and set the maximum frequency of contraction for each part of the GI tract
For Spike potentials, describe their potentials, when they occur, and what they are responsible for at the molecular level.
Spike potentials ARE action potentials that occur automatically when the resting membrane potential of the GI smooth muscles becomes more positive than -40 mV
These are responsible for opening/closing calcium-sodium channels in GI smooth muscle cells
The following are all what type of GI reflexes?
Much of GI secretion
Peristalsis
Mixing contractions
Local inhibitory effects
Reflexes that are integrated ENTIRELY within the gut wall enteric nervous system
The following are all characterisitc of what type of GI reflexes?
Transmit signals long distances to other areas of the GI tract
Cause evacuation of the colon (gastrocolic reflex)
Inhibit stomach motility and secretion (enterogastric reflex)
Empty ileal contents into the colon (colonoileal reflex)
Reflexes from the gut to the prevertebral sympathetic ganglia and then back to the GI tract
For Gastrin, state the function, what secretes it, what stimulates this secretion, and what inhibits it’s secretion.
Gastrin: stimulates gastric acid secretion by parietal cells AND stimulates mucosal growth (by stimulating synthesis of RNA and new protein)
Secreted by the G cells of the small intestines in response to the distension stimuli after eating a meal
Secretion is stimulated by distention/vagal stimulation via GRP (gastrin-releasing peptide)
Secretion is inhibited acid from the stomach or somatostatin
For Cholescystokinin (CCK), state the action, what cells secrete it, and the stimulus for it’s secretion.
CCK (cholecystokinin):
Controls the Feedback of the Duodenum
Stimulates pancreatic secretory functions and contraction of the gallbladder and relaxation of the sphincter of Oddi (to allow the secretion of bile). Inhibits gastric emptying, and appetite.
Secreted by the I cells of the small intestine
Secretion is stimulated by fatty acids and monoglycerides
For Secretin, state it’s action, what cells it is secreted by, and what stimulates it’s secretion
Secretin: Stimulates pepsin secretion, bicarbonate secretion, exocrine pancreas growth. Inhibits gastric acid secretion by parietal cells.
Secreted by the S cells of the small intestine
Secretion is stimulated by Acid and fat in the lumen of the duodenum
For GIP, state it’s action, what cells secrete it, and what stimulates it’s secretion.
Gastric Inhibitory Peptide (GIP): Stimulates insulin release (to bring blood glucose down) and inhibits gastric acid secretion by parietal cells
Secreted by the K cells of the duodenum and jejunum
Secretion is stimulated by protein, fat, and/or carbohydrates entering the GI tract (also secreted in response to oral glucose)
For Motilin, state it’s action, what cells secrete it, and what stimulates it’s secretion.
Motilin: stimulates gastric acid and intestinal motility
Secreted by the M cells of the duodenum and jejunum during times of fasting
Secretion is stimulated by Fat, Acid, or nerve action?
