Motility Of The GI Tract Flashcards
What organs primarily use Tonic contractions?
1) Stomach (orad part)
2) lower esophagus
3) ileocecal
4) internal anal sphincters
What is it called when a sub threshold depolarization produces a weak contraction?
Basal contractions
What 3 things increase the amplitude of the slow wave?
1) stretch
2) Acetylcholine
3) parasympathetics
What 2 things cause cause hyper polarization?
Norepinephrine and sympathetics
What plexus controls GI secretions and local blood flow?
Submucosal (meissners)
What plexus controls GI movements?
Myenteric (Auerbach’s)
Where do slow waves originate from?
Interstitial cells of cajal (ICC)
How do slow waves move from pacemaker region to smooth muscle?
Gap junctions
Smooth muscle cells respond to slow wave depolarizations with increased what?
Permeability of Ca+2 because probability of channels opening increases
What are the 3 phases of swallowing?
1) Oral Phase (voluntary)
2) Pharyngeal phase
3) Esophageal phase
Walk through what happens in the pharyngeal phase of swallowing
Soft palate is pulled upward –> epiglottis moves –> UES relaxes –> peristaltic wave of contractions is initiated in pharynx –> food is propelled through open UES
Which phase of swallowing takes the longest?
Esophageal phase (8-10 seconds)
What 2 things control the esophageal phase of swallowing?
Swallowing reflex and the ENS
The involuntary swallowing reflex is controlled by what?
The medulla
What is the somatosensory information that signals from the pharynx to the swallowing center in the medulla?
Food in the mouth
What 3 nerves can carry afferent info from the pharynx to the medulla in response to food in the mouth?
1) Vagus
2) Glossopharyngeal
3) Trigeminal
During the pharyngeal phase of swallowing, the swallowing center inhibits what?
The respiratory center
The primary peristaltic wave of the esophageal phase of swallowing is controlled by what?
Medulla (swallowing center)
The primary peristaltic wave CANNOT occur after this procedure?
Vagotomy
What induces a secondary peristaltic wave?
- if primary contraction fails to empty the esophagus or when gastric contents reflux into the esophagus
- Induced by distention of the esophagus itself by the retained food
What controls the secondary peristaltic wave?
Both the swallowing center and the ENS
Can a secondary peristaltic wave occur after Vagotomy?
YES
What organs primarily use Phasic contractions?
1) esophagus
2) Stomach (Antrum/caudad)
3) small intestine
4) all tissues involved in mixing and propulsion
Gastroesophageal reflux occurs when intra-abdominal pressure is increased. Give two examples of when this happens.
Pregnancy and morbid obesity
What neurotransmitter is used by the vagus nerve to relax the lower esophageal sphincter to pass a bolus of food into the stomach?
VIP
Opening of the LES is mediated by what type of fibers in the vagus nerve?
Peptidergic
What tests would you order when a patient presents with symptoms that lead you to believe they have Achalasia?
manometric recording and barium swallow
Receptive relaxation occurs in what region of the stomach?
Orad
What does receptive relation do to pressure and volume?
Decreases pressure and increases volume
Receptive relaxation is what kind of reflex?
Vagovagal
Describe the contractility of the Orad region
Little contractility
Receptive relaxation of the stomach is controlled by what neurotransmitter of the Vagovagal reflex?
VIP
Describe the change in contractions from the mid stomach to the pylorus
Increase in both force and velocity
What is it called when food moves back from pylorus into the stomach?
Retropulsion
What increases the number of action potentials and the force of contractions? 3 things
1) Parasympathetics
2) Gastrin
3) Motilin
What 3 things decrease the number of action potentials and force of contractions?
1) sympathetics
2) Secretin
3) GIP
How long does gastric emptying take?
3 hours
Whenever there is fat or protein in the food bolus, gastric emptying is decreased by increasing gastric distensibility by what?
CCK
Acid in the duodenum stimulates what?
Secretin release –> inhibit stomach motility via Gastrin inhibition
Fats in duodenum stimulate what?
CCK and GIP –>inhibit stomach motility
How would you treat diabetic gastroparesis?
lower blood glucose
Large particles of in digested residue remaining in the stomach during FASTING are emptied by what?
Migrating myoelectric complexes (MMC)
MMC’s are mediated by what hormone?
Motilin
How does frequency of contraction change as food moves through the small intestine?
There is a decrease in the frequency as the bolus moves towards the ileocecal junction
What is released from enterochromafin cells in response to a chemical or mechanical stimulation and what does it bind to?
- Serotonin
- IPANs
What coordinates the vomiting reflex?
Medulla
What stimulates the chemical trigger zone in the vomitting reflex?
Apomorphine and morphine
Major excitatory mediators of the large intestine?
ACh and substance P
Major inhibitory mediators of large intestine?
NO and VIP
Distal rectum and anal canal get sympathetic innervation from what?
Hypo gastric plexus
External and internal anal sphincters get sympathetic innervation from what?
Somatic pudendal nerves