Gut Motility Flashcards
Effect of CCK on Gallbladder, Pancreas, Stomach, Sphincter of Oddi:
Gallbladder: Contraction
Pancreas: Acinar secretion
Stomach: Reduced emptying
Sphincter of Oddi: relaxation
What causes release of CCK?
Ach
CCK-releasing peptide
Gastrin releasing peptide
What inhibits CCK release?
Trypsin by degrading CCK-RP
Where is secretin produced?
In the duodenum by S cells
When is secretin released?
In response to low pH and polypeptides
Effect of increased Ca++ intracellularly:
Contraction
Effect of increased cAMP intracellularly:
Relaxation
Effect of Ouabain:
Inactivates the Na/K pump to causing a buildup of Na intracellularly
What are the effects of cAMP and Ca++ on intestinal secretions?
Increase of cAMP and Ca cause an increase in secretions by stimulating epithelial cells to transport ions in to the lumen (causing the rhea)
How does the NaCl transport process drive the absorption of short-chain fatty acids in the colon?`
Using the sodium-monocarboxylate transporter (SMCT) it uptakes SCFA and Na (Na/K pump pumps out the Na)
What is needed for expression of the SMCT?
SMCT1 gene (reduction results in some colon cancers)
What layer are the Interstitial cells of Cajal found?
Muscularis externa
How does SM action potentials differ from other muscle types?
They are much longer resulting in slow wave contractions
What is the effect of epi and norepi on the SM AP?
It causes a hyperpolarization so that Ca channels cannot be activated and muscle relaxes
What is the effect of VIP and NO on SM?
Relaxation
Effect of Ach and substance P on SM?
Contraction
What does a SM look like at a rest?
Has slow wave contractions
What does the SM AP look like when food is ingested?
Slow wave with spikes on top of them due to Ach and Sub P release
What is the muscle composition of the esophagus?
Proximal portion is skeletal muscle
Distal portion is smooth muscle
Why does the LES have increased pressure?
To stop gastric acid from coming out to the esophagus
What nerve causes relaxation of the esophagus?
Vagus (releasing NO and VIP)
How does a bolus move?
Dorsal vagus complex releases NO at the distal end of the bolus and Ach at the proximal end
What does residual food cause?
A secondary peristaltic event to clear the food
What occurs when the stomach is full?
Stretch receptors are activated causes a release of CCK that acts on DVC releasing NO and VIP to cause relaxation
Where in the stomach are the pacemaker cells found?
Greater curvature (where the slow waves are generated)
What occurs during times of fasting?
A very slow wave of muscle contraction moves from the stomach all the way down to the end of the SI; does not occur in the colon (would cause defecation)
What are the muscle compositions of the anal sphincters?
Internal: Smooth muscle
External: Skeletal muscle
What occurs in the defecation reflex?
Sensing the rectum is full an impulse is sent to relax the internal anal sphincter
What does CCK act on?
Dorsal vagal complex to facilitate gallbladder contraction and relaxation of the Sphincter of Oddi
What is achalasia?
The LES is contracted/not relaxed so esophagus gets distended
