Gut motility GI week 2

Question Answer
give two areas of the GI tract that are under voluntary control upper oesophageal sphincter (swallowing), and external anal sphincter (defecation)
what two types of muscle are in the musuclaris? circular muscle and longitudinal muscle
what mediates enteric neurotransmission? interstitial cells of Cajal
what do the myenteric interstitial cells of Cajal do? serve as a pacemaker which creates the bioelectrical slow wave potential that leads to the contraction of smooth muscle
what does the enteric nervous system mediate? reflex activity in the absence of CNS input (interprandial period)
what extrinsic factors influence the enteric nervous system? vagal control: excitatory to non-sphincteric muscle, sympathetic control: inhibitory to non-sphincteric muscle, excitatory to sphincteric muscle
give three neurohormonal influences on the enteric nervous system Motilin, opioid receptors, 5-hydroxy-tryptamine
measurement of motility function: transit radiolabelled isotopes (breath tests and scintigraphy), dynamic contrast radiology
what sort of muscle does the upper and lower oesophagus have? upper – circular. lower – longitudinal
name two conditions that can affect the striated (upper part) of the oesophagus polymyositis (chronic inflammation of muscles) and myasthenia gravis
give two conditions that can affect the smooth muscle (lower part) of the oesophagus scleroderma hard, thickened areas of skin) and achalasia
what happens in achalasia your lower oesophageal sphincter fails to open during swallowing, so there's a backup of food in your oesophagus
give four disorders of oeosphageal motility achalasia, nutcracker/jackhammer oesophagus, diffuse oesophageal spasm, oesophageal involvement in scleroderma
give treatments for achalasia rigiflex balloon dilation, laparoscopic heller's myotomy, per oral endoscopic myotomy (POEM)
what's the oesophagus like in scleroderma weak lower oesophagel sphincter, absent peristalsis, severe oesophagitis
what's nutcracker oesophagus associated with pain on swallowing, functional swallow tho
two motility phases of stomach and small intestine the interprandial period and the fed state
what complex is active during the interprandial (fasting) period? the migrating motor complex
how frequently does the migrating motor complex occur? every 90 minutes – it's a cyclic contraction sequence
what's the migrating motor complex regulated by? motilin
what does the migrating motor complex act to do? cleanse stomach and intestine
name the four phases of the migrating motor complex prolonged period of quiescence, increased frequency of contractility, a few mins of peak electrical and mechanical activity, declining activity merging to next phase 1
what is motilin and what is it produced by? polypeptide hormone produced by M cells in small intestine
when is motilin secreted? at 90 minute intervals
what does motilin act as? 'housekeeper' of the gut – cleanses in time for next meal. stimulates contraction of gastric fundus and enhances gastric emptying
name a motilin agonist erythromycin
describe the cephalic phase secretory phase, vagally mediated, sight/smell of food leads to increased gastric secretion
what percentage of gastric secretion happens in the cephalic stage? 20%
what happens in the gastric phase? proximal gastric tone reduces and fundus expands to accommodate meal. stomach expands without increase in pressure
what's the mmc replaced with in the gastric phase? by contractions of variable amplitude and frequency, allowing mixing and digestion
what's the frequency and direction of gastric muscular contractions controlled by? 'gastric pacemaker' zone within proximal gastric body
what does the gastric pacemaker zone do? generates rhythmic depolarisations at a frequency of 3 cycles per minute, which only trigger gastric smooth muscle contractions with additional neurohormonal input
what' s the emptying time for liquids in the stomach? emptying time for inert liquids is 20 mins, liquids leave stomach earlier than solids, solids undergo mixing and churning
how long do solids take to empty empty completely over 3-4 hours
what slows down gastric emptying? nutrient content – fatty meals take longer to leave the stomach
how much per hour is delivered to duodenum for liquid foods? 200kCal/hr
give 2 disorders of accelerated gastric emptying dumping syndrome and diarrhoea
give four disorders of delayed gastric emptying abdo pain, vomiting, malnutrition, poorly controlled gastro-oesophageal reflux