Smooth muscle in the GIT

cgeorge's version from 2016-02-22 16:24


Question Answer
Skeletal muscle is found in thePharynx, top third of oesophagus ,external anal sphincter
Phasic contractions areRapid contraction and relaxation. Found in oesophagus, antrum of stomach, SI/LI
Tonic contractions aresustained. Found in sphincters (LOS)
Role of Intestitial cells of CAJALServe as pacemaker, generate spontaneous electrical slow wave which spread from ICC to smooth muscle cells, resulting in depolarization > contraction
Key feature of ICC'SSpontaneous oscillating membrane potential
3 Stimulants of depolarisation of smooth muscle fibers1) Ach 2) Stretch 3) Parasympathetics
3 stimulants of hyperpolarisation of smooth muscle fibers1) Noradrenaline 2) Sympathetics
In order for myosin to bind to actin mysoin needs to be Phosphorylated
In order to phosphorylate myosin we need to Activate the MLCK
Activation of MLCK requiresCa/calmodulin protein complex
Calcium comes from 2 sources;1) Voltage dependent Ca channels 2) Phospholipase C pathway
Main mechanism to return cell [Ca] levels to normalCalcium reuptake into the SER by the SERCA pump
Relaxation of smooth muscle requiresDephosphorylation of the myosin light chain which needs MLCK phosphatase
Role of MLCK phosphatase?Dephosphorylation of the myosin light chain
Phosphorylated MLCK means thatIt cant bind to the Ca/calmodulin protein binding complex, causes relaxation event cus you cant phosphorylate the myosin
Hormone that causes a relaxation eventB-adrenergic VIP results in phosphorylated MLCK
Myenteric plexus is located betweenCircular and longitudinal muscle
Submucosal plexus is betweenCircular and submucosa
Propulsive movements are responsible forPeristalsis
Peristalsis occurs in which stage?The fed stage
Non propulsive movements are responsible forSegmentation = Mixing function, increasing SA, break chyme/bolus up.
Migrating motor complex occurs in which stage?The fasting stage
Segmentation occurs in which stage?The fed stage
Hirschsprung diseaease is a result ofCongenital lack of neuronal ganglionic cells in the ENS plexus
Chagas disease is a result ofSignificant reduction in the no. of ganglionic cells in the END
Achalasia is a Reduction in the no. of neuronal cells in the lower oesophageal segment
What part is always involved in hirschprungs disease?Anus
Mutation in RET gene causes?Hirschsprungs disease
The protozoan parasite .... causes Chagas diseaseTypanosoma cruzi
Empty stomach volume = 50ml
Upon filling of stomach, intraluminal pressure .... changesDoesnt really change
Vago-vagal reflex regulatesRelaxation in the fundus
3 stages of gastric motility1) Propulsion 2) Grinding 3) Retropulsion
Propulsion is Rapid flow of small particles and delayed flow of large particles towards pylorus
Grinding isBolus trapped near the antrum is churned to help reduce the size of the particles
Retropulsion is When most of the gastric contents are returned to the body of the stomach for shearing of solid particles
Anything bigger than .. mm wont make it through pylorus2
Pylorus sphincter function;1) Allows regulated emptying of gastric contents 2) Prevents regurgitation of duodenal contents into stomach 3)Prevents bile rich SI secretions going back into stomach
3 phases of gastric emptying1) cephalic 2) gastric 3) intestinal
Is cephalic phase an inhibitory or excitatory phase?Inhibitoyr - Inhibitory nerve fibers in the vagus nerve. Results in relaxation of stomach
Is gastric phase an inhibitory or excitatory phase?Excitatory.
Stomach empties in the gastric phase due to;1) Myogenic reflex (stretchin of smooth muscle) 2) activation of pressure receptors 3) gastrin released in response to peptides
Is intestinal phase inhibitory or excitatory phase?Inhibitory
Explain the ileogastric reflexChyme entering ileum activates pressure receptors which delays gastric emptying via nerves in plexi