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
Secretin site of secretion
S cells
Secretin function
Stimulates pepsin secretion, pancreas and gall bladder
Inhibits gastrin
Glucose-dependent insulinotropic peptide site of secretion
K cells (duodenum and jejunum)
Glucose-dependent insulinotropic peptide action
Stimulates insulin release
Inhibits acid secretion
Motilin site of secretion
M cells (duodenum and jejunum)
Substance secreted due to vagal stimulation of gastric mucosa
Gastrin-releasing peptide
Cholecystokinin actions
Contracts gallbladder, slows gastric emptying. Inhibits apetite
Stimulus for peristalsis
Gut distention
liver sinusoids lined by ______. Function?
Reticuloendothelial cells
Funcion is to remove bacteria from portal circulation
mechanics of the pharyngeal stage of swallowing:
The trachea is closed, the esophagus is opened, and a fast peristaltic wave initiated by the nervous system of the pharynx forces the bolus of food into the upper esophagus
Sensory impulses in mouth go to
Tractus solitarious
Areas in medulla/pons controlling swalloing
Deglutition
Swallowing center
Primary vs secondary esophagus peristalsis
Primary: Follows first wave of food down
Secondary: remaiing food distends esophagus and initiates second wave
Waves that mix food in stomach
Constrictor waves/ mixing waves
Maximum segmental contraction frequency determined by
Frequency of slow waves in intestinal wall
gastroileal reflex
intensifies peristalsis in the ileum and forces the remaining chyme through to large intestine.
Longitudnal strips of muscle in colon AKA
Teniae coli
External anal sphincter controlled by
Pudendal nerve
Parasympatheic defecation reflex
Chyme in rectum stimulates nerves that synapse at spine and then return via pelvic nerves to cause peristalsis
Peristalsis during peritonitis
Inhibited