Lecture 5: Motility of GI System Flashcards
What does motility involve?
Contraction and relaxation of the walls and sphincters of the GI tract
What are the layers of the GI tract, inside to outside?
1. Epithelium 2 . Lamina propria (connective tissue) 3. Muscularis mucosae 4. Submucosa -----Submucosal/Meissner Plexus------ 5. Circular Muscle -----Myenteric Plexus----- 6. Longitudinal Muscle 7. Serosa
What consists the muscularis mucosae?
Smooth muscle and its contractions
Shape and surface area of the epithelium
During contractions, what does the circular muscle do?
Reduce diameter of segment
During contractions, what does the longitudinal muscle do?
Length of segment
Describe slow waves.
Depolarization and repolarization of the membrane potential to allow action potentials to occur more easily
-when membrane potential crosses threshold, AP can occur
What are phasic contractions?
Periodic contractions followed by relaxation
Which organs utilize phasic contractions?
Esophagus
Antrum of stomach
Small intestine
Tissues involved in mixing and propulsion
What are tonic contractions?
Constant level of contraction w/o regular periods of relaxation
Which organs utilize tonic contractions?
Orad of stomach
Lower esophagus
Ileocecal junction
Internal anal sphincters
What NT increases the amplitude of slow waves and action potential?
Acetylcholine
What NT decreases the amplitude of slow waves and action potential?
Norepinephrine
What does the Submucosal (Meissner) Plexus control?
GI secretions and local blood flow
What does the Myenteric (Auerbach’s) Plexus control?
GI movement
What cells are considered the pacemaker cells of the GI system - generate and propagate slow waves?
Interstitial cells of Cajal
