Phsiologic Anatomy of the GI wall - Enteric NS Flashcards
measurement of individual muscle fibers in the GI tract
200-500 micrometers long and 2-10 micrometers in dm
Longitudinal muscle layer
extends longitudinally down the intestinal tract
circular muscle layer
bundle extends around the gut
gap junctions
found within each bundle
where can electric signals travel faster
along the length of the bundle
what separates each bundle of smooth muscle but not on its entirety?
loose connective tissue
How is branching lattice work of smooth muscle formed?
When muscle fibers fuse with one another at any joints
syncytium
when an action potential is elicited anywhere within the bundle masa, it generally travels in all directions in the muscle
How is the electrical activity of the GI smooth muscle?
Continuous but slow
2 basic type of electrical activity
Slow waves and spikes
Intensity in slow waves
between 5 and 15 mv
Frequency in the stomach, duodenum and ileum during slow waves
stomach (3/min)
duodenum (12/min)
ileum (8-9/min)
interstitial cells of cajal
electrical impulse in the slow waves
Normal resting membrane potential in the smooth muscle fibers of the gut
-50 to -60 mv
spike potentials frequency
1-10 spikes/s
the normal resting membrane potential
-56 mv
depolarization
potential is less negative, muscle fibers more excitable
hperpolarization
potential is more negative, fibers less excitable
When do spike potential occur?
When resting membrane potential of the gi smooth muscle becomes more positive than -40 mv
Calmodulin control mechanism
causes muscle contraction by activating the myosin filaments in the fiber
Enteric nevrous system
-lies in the wall of the gut from esophagus to anus and controls gi movement and secretion
2 plexus of the enteric nervous system
Myenteric plexus (Auebach’s) and submucosal plexus (meisner’s)
Auerbach’s plexus
controls gi movements
Meissners plexus
gi secretion and local blood flow
