GI tract motility Flashcards
what is the inner smooth muscle layer of the stomach
oblique
what is the middle smooth muscle layer of the stomach
circular
what is the outer smooth muscle layer of the stomach
longitudinal
where does the muscle wall thickness increase
proximal to distal
where do contractions happen to mix food and propel it to the small intestine
caudad region
what are the 3 layers of the stomach wall
serosa
muscularis externa
rugae of mucosa
how does the PSNS affect the stomach
increases muscle contractions and secretion
what is the parasymp supply to the stomach
vagus
what is the symp supply to the stomach
coeliac ganglion
where are the sensory afferent fibres to the stomach
between the sensory receptors and the ENS and centrally via the vagal and splanchnic nerves
what are the orad and caudad regions of the stomach
orad- towards the mouth
caudad- towards the feet
what does distension of the lower oesophagus induce
relaxation of the lower oesophageal spincter and orad
what afferent information is relayed from the stomach
mechanoreceptors associated with chewing and distension
via sensory neurones
what neurotransmitter causes orad relaxation when released from post gangionic peptidergic vagal neurones
vasoactive intestinal peptide
how does the caudad contract
contraction waves begin in the middle and move towards the pylorus
what is retropulsion
moving the gastric contents up for further mixing
describe slow waves
generated by the interstitial cells of Cajal
when slow waves reach a certain potential then then L type ca channels open and contraction can occur
what stimulates action potentials in slow waves
stretch
ach
parasympathetics
what stimulates hyperpolarisation of smooth muscle
norepinephrine
sympathetics
how does the para and sympa NS innervate the stomach
sympa - coeliac ganglion
para- vagua
where is the submucosal plexus
between the muscularis mucosa and the submucosa
where is the myenteric plexus
between the circular and longitudinal muscle layers
what is the vagovagal reflex
controls relaxation of the stomach in response to food
what are the three movement patterns in the stomach
propulsion
grinding
retropulsion
what factors increase action potential frequency from slow waves
Parasympathetic stimulation, gastrin and motilin
what factors decrease action potential frequency from slow waves
Sympathetic stimulation and secretin
what hormone mediates migrating myoelectric complexes
motilin
what is the frequency of slow waves in the ileum
9 per minute
how often do MMCs happen
every 90 minutes to clear the small intestine of chyme
what hormones stimulate orad contraction
ACh and substance P
what substances control caudad contration
VIP nitric oxide
what muscle is found in the large intestine
circular and longitudinal (tenia coli)
what do pelvic nerves do to the distal colon
stimulate expulsive contrations
how many times a day do mass movements of the large intestine occur
1-3 times
final movement propels faeces into the rectum
what reflexes cause mass movements
gastrocolic and duodenocolic
this is because food further up the tract increases movement in the colon
what do CCK and gastrin do in the gastrocolic reflex
efferent limb of reflex
what is the rectosphincteric reflex
the relaxation of the internal anal sphincter
