GI Tract Flashcards
what does the enteric nervous system control
controls GI motility and secretion
What 2 interconnected plexuses are in the gut wall and what do they control
Myenteric-motility
submucosal- secretions and local blood flow
The ENS has reflex contractions in response to local stimuli which are?
stretch, nutrients, irritation and hormones
What effect does parasympathetic innervation have
Excitatory to motility and secretion
what effect does sympathetic innervation have
inhibitory to motility and secretion
What are the two types of electrical activity in the gut smooth muscle cells
slow waves and spike potentials
describe slow waves
provide a basic electrical rhythm via interaction with interstitial cells of cajal
describe spike potentials
causes contraction by further depolarisation to threshold levels
What are the two types of contractions
segmentation- back and forth pendular movements, for mixing
peristalsis- wave of contraction- for propulsion
Give an example of ENS innervation dysfunction
Hirschsprung’s disease= absence of myenteric plexus resulting in aganglionic section of colon lacking peristalsis
what are the 3 stages of swallowing (deglutition)
Oral, pharyngeal and oesophageal
Give an example of Oesophageal motility dysfunction
Gastro-oesophageal reflux: LOS tone lost leading to flow of acidic gastric contents into oesophagus, results in inflammation and ulceration.
What are the 3 primary motor functions of the stomach
storage: vagovagal reflex mediates receptive relaxation to allow reservoir function
mixing: breaking down food and mixing it with gastric juice for digestions
emptying contents into duodenum at a controlled rate.
What controls the emptying of the stomach
excitatory -stimulated by motilin and PSMNS
Inhibitory- Via CCK, ANS (stimulation)
Name 3 propulsive peristalsis reflexes
gastroenteric reflex
gastroileal reflex
migrating motor complex
describe the gastroenteric reflex
gastric distention activates myenteric plexus to promote SI peristalsis
describe the gastroileal reflex
gastric distention promotes peristalsis in ileum to force chyme via ileocaecal valve into caecum
describe the migrating motor complex
series of peristaltic contractions, between meals, every 90 min sweeps contents into the colon.
name 3 disruptions to peristalsis
peristaltic rush, paralytic ileus and vomiting
describe the peristaltic rush
mucosal irritation, ENS and ANS reflexes which rapidly sweeps contents of SI into colon
describe the paralytic ileus
loss of peristalsis following mechanical trauma
describe the defacation reflex
mass movement pushes shit into the rectum, stretch receptors are stimulated and activate the ENS & PSM ANS, involuntary contraction of muscle in the rectum opening internal anal sphincter. external anal sphincter is voluntarily relaxed to allow defacation.
