L29 - Control of GI tract motility Flashcards
list main functions of GI tract
- digestion
- absorption of nutrients&electrolytes
- water absorption
- immune function
in what layer of the GI tract do absorbed nutrients enter blood / lymph
submucosa
the enteric nervous system is composed of what nerve plexuses
submucosal nerve plexus
myenteric nerve plexus
what is the extrinsic control of motility
ANS
what is the intrinsic control of motility
enteric nervous system (myenteric and submucosal nerve plexus’s)
what is the long reflex for motility control
- receptors in GI detect stimuli in lumen
- send signal to CNC
- CNS sends signal to enteric nervous system
- effect (on SM / gland)
what is the short reflex for motility control
receptors in GI detect stimuli and send signal straight to enteric nerve plexus’s
what are the 3 main contractions that occur in GI tract
peristalsis
segmentation
pendular contractions
what is peristalsis
rhythmic contractions of circular and longitudinal muscle
what is segmentation
powerful contraction of circular muscle to break up food
what is pendular contractions
powerful contractions of longitudinal muscle
what receptors mediate deglutition and where are they located
mechanoreceptors in pharynx
where is the swallowing centre located
medulla oblogata
describe deglutition process
- food at back of pharynx stimulates mechanoreceptors which sends signal to swallowing centre which initiates swallowing reflex
2.
the swallowing centre sends efferent impulses via what pathways
vagus nerve
glossopharyngeal nerve
describe process of swallowing reflex
(involuntary pharangeal phase)
- soft palate elevates preventing food entering nasal passages
- epiglottis covers glottis preventing food into lungs
- respiration ceases
- upper oesophageal sphincter relaxes
- pharynx strongly contracts
- initiates involuntary oesophageal phase
- peristaltic wave moves food to stomach
- lower oesophageal sphincter relaxed so food can enter stomach, then it closes
what initiates peristaltic contractions (in stomach)
pacemaker cells in longitudinal layer
what happens to the peristaltic wave in the regions of stomach
produces only a ripple to antrum, where it produces a more powerful contraction mixing food
describe the basal electrical rhythm of stomach
slow depolarisation-repolarisation waves in longitudinal muscle (that induce circular muscle through gap junctions) - don’t always produce contraction
what factors increase frequency and force of peristaltic contractions
PNS
Gastrin
motilin
what factors decrease frequency and force of peristaltic contractions
SNS
secretin
name two enterogastrones
secretin
CCK
what stimulates secretin
acid in duodenum
what stimulates CCK
AA and FAs in SI
what stimulates gastrin
PNS
peptides/AA in stomach
what inhibits gastrin
stomach acid and somatostatin
what is the function of motilin
induces migrating myoelectric complex (MMC)
what is the migrating myoelectric complex and what is its function
peristaltic waves that spread through SI and consecutively start further along until large intestine
empties stomach and SI of remaining chyme
what is the intrinsic control of gastric emptying
short reflexes due to duodenum distension
what inhibits gastric emptying
SNS
CCK
Secretin
what promotes gastric emptying
PNS
