[3] GI Motility Flashcards
Function: Upper Esophageal Sphincter
Prevent reflux of food into the respiratory tree
Prevent too much air coming in when we breathe
Why don’t we want too much air in our gut?
Prevent feeling full
Avoid increased abdominal pressure
Function: Lower Esophageal Sphincter
Prevents reflux of food
Allows food to enter the stomach
Which is more important for incontinence? Internal or External Anal Sphincter?
Internal: About 80%
What controls electrical activity and coordinates it in the GI Tract?
Cells of Cajal
Contraction uses about how much % of the energy of striated muscle?
1%
What activates Myosin Light-Chain Kinase?
Ca2+ + Calmodulin
2 Basic Types of Electrical Activity of GI Smooth Muscle
Slow Waves
Spike Potentials
At what action potential will a spike be generated?
< - 40mV
What stimulates spikes?
Stretch
Acetylcholine
Parasympathetics
Types of GI Movements
Phasic
Tonic
Define: Phasic GI Movement
Short, rhythmic, and promotes efficient mixing and transit of chyme
Define: Tonic GI Movement
Long, sustained, serve to limit flow or provide reservoir
What is responsible for Orad Contraction?
ACh and Tachykinins
What is responsible for Caudad Contraction?
VIP and Nitric Oxide
What do you call the rumblies in your tumsies?
Migratory Motor Complex
What initiates the rumblies?
Motilin
Phases of MMC
I: Quescence
II: Irregular contractions fail to propel luminal contents but contractive activity increases
III: 5-10 minutes, intense luminally occlusive contractions; pylorus fully open allowing clearance of indigestible residues
Extrinsic Regulator of GI Motility
ANS
Parasympathetic: Vagus, Pelvic Nerves
Sympathetic: Thoracolumbar Portion of Spinal Cord
Why are malignancies not common in the small bowel?
Food passes through it pretty quickly
What produces primary peristalsis of the esophagus?
Swallowing
What relaxes during swallowing?
Lower Esophageal Sphincter
Stomach
Would you feel hungry or full if your stomach is not relaxing when you swallow?
Full
What muscle is located in the UES
Cricopharyngeus
Describe the Esophagus at Rest
Like a sausage, UES and LES with tonic contractions
Control of UES and LES
UES: Nervous
LES: Nervous + Hormonal
UES Pressure Increased By
Respiration
Distention
Stress
UES Pressure Decreased By
Sleep
Anesthesia
Most common cause of Gastroesophageal Reflux
Transient LES Relaxation
Function: Proximal Stomach
Storage
Why does vagotomy cause patients to feel full faster?
The stretching phenomenon of the stomach is mediated by the Vagus
Functional: Distal Stomach
Mixing and Propulsion of Food
What part of the GIT has the most contractility?
Stomach: 3
Duodenum: 12
Ileum: 8-9
Colon: 6
Contractions / Minute
Gastric Factors that Promote Emptying
Components of Gastric Content
Time of Food Intake
Gastrin
Gastric Factors that Inhibit Emptying
High lipid
High H+ ion
Increased osmolality
Tryptophan
General Trend of Reflex Naming
If the distal part is the first part of the name, it would be inhibitory
(Enterogastric Reflex: Inhibitory)
[Enterogastric Reflex]
Acids cause secretion of?
Secretin
[Enterogastric Reflex]
Fats cause secretion of?
GIP, CCK
[Enterogastric Reflex]
Amino Acids/Peptides cause secretion of?
Gastrin
Define: Vomiting
Forceful expulsion contents of stomach and upper intestinal tract
What coordinates Vomiting?
Vomiting Center in the Medulla
At what phase of the MMC does 25% of the Gallbladder secrete bile?
Phase II
What causes Gallbladder contraction?
ACh and CCK
What causes Sphincter of Oddi relaxation?
CCK
