Motility of GI Tract - Lopez Flashcards
Which elements of the GI Tract Wall comprise the Mucosal Layer?
Epithelium
Lamina Propria
Muscularis Mucosae
Which elements of the GI Tract Wall comprise the Muscularis Propria?
Circular Muscle
Myenteric Plexus
Longitudinal Muscle
Note: Important for motility of GI
What are the characteristics of Circular Muscle? Longitudinal Muscle?
Circular M. - Thick muscle with dense innervation; Contraction —> DECREASE diameter
Longitudinal M. - Thin muscle with fewer innervations; Contraction —> DECREASE length of segment
What are Slow Waves? How do they differ from Action Potentials?
Slow Waves - depolarization/repolarization of membrane, whose frequency is set by the Interstitial Cells of Cajal found in the Myenteric and Submucosal Plexuses.
Action Potentials - Depolarization moves membrane at or above threshold.
How are Action Potentials and strength of contraction modulated?
Neural Activity and Hormonal Activity
What is a Phasic Contraction? Where do these contractions occur?
Periodic contraction followed by relaxation; Esophagus, Stomach (Antrum), SI, Tissue involved in mixing/propulsion.
What is a Tonic contraction? Where do these contractions occur?
Maintain constant level of contraction without regular period relaxation; Stomach (orad), Lower Esoph., Ileocecal, and Internal Anal Sphincter.
What is the relationship between Slow Waves, APs, and Contractions in smooth muscle?
GREATER number APs on a slow wave —> INCREASED contraction of smooth muscle segment
What is the effect of ACh on the amplitude of Slow Waves? NE?
ACh —> INCREASE amplitude slow wave
NE —> DECREASE amplitude slow wave
How does STRETCH impact the amplitude of slow waves?
INCREASE amplitude
What effect do the Parasympathetic and Sympathetic have on Slow Wave amplitude?
Parasympathetic —> INCREASE amplitude
Sympathetic —> DECREASE amplitude
Hyperpolarize so difficult to reach threshold
What is controlled by the Submucosal (Meissner) Plexus?
GI Secretions
Local Blood Flow
What is controlled by the Myenteric (Auerbach’s) Plexus?
GI Movement
Which cells are the “Pacemaker” cells for GI smooth muscle?
Interstitial Cells of Cajal (ICC)
Propagate slow waves —> spread via gap junctions
Which nerve supplies most of the muscles of mastication?
Motor branch of 5th Cranial Nerve (Trigeminal)