Phys 63-64: GI Principles and Propulsion Flashcards
GI Wall muscle layers (out to in)
1) Serosa
2) Longitudnal
3) Circular
4) Submucosa
5) Mucosa
What happens in a muscle that functions as syncytium
Action potential in one area travels in all directions of muscle
Two types of electrical waves in GI muscle
Slow wave
Spike
Slow waves are caused by _____
Undulating changes in resting membrane potential
Electrical pacemakers of smooth muscle cells aka
Interstitial cells of cajal
Ion channels in nerve fibers (which ions?) (in GI*)
Calcium-sodium channels
Lots of calcium and sodium
Factors that depolarize GI smooth muscle membrane
1) Stretching of muscle
2) Stimulation by acetylcholine
3) Simulation by specific GI hormones
Factors that make GI smooth muscle membrane less excitable
1) Norepi/Epi
2) Sympathetic
Calcium ion influx into smooth muscle causes
Contraction.
Tonic contraction characteristics
Non-rhythmic. Continous and last several minutes-hours
Myenteric vs submucosal plexus
Myenteric: GI movement
Submucosal: Secretion
Enterogastric reflexes
Intestine tells stomach to chill
Gastrocolic reflex
Stomach tells colon to move
(la de hoy empuja la de ayer)
Gastrin secretion site
G Cells of antrum
Gastrin action
stimulates gastric acid secretion and mucosal growth