Flashcards
Gastrointestinal motility
Cards in this deck (38)
- 1Give the 4 basic functions of the GI tract1 - motility
2 - secretion
3 - digestion
4 - absorption - 2Which 2 functions have the greatest degree of controlsecretion and motility
- 3How is gut motility achievedlayers of smooth muscle - along length of gut
circular and longitudinal - 4What 4 things does the sequenced contraction and relaxation of muscle layers allow for1 - mixing of ingested food with secretions
2 - mechanical breakdown of food
3 - propulsion of food along gut tube
4 - periodic release of chyme through sphincters from one region to the next - 5How many layers are in the gut tube and what 2 things do variations depend on- 4
- variations depend on level/function of gut segment, species/foodtype - 6What 4 layers comprise the basic gut tube- mucosa - protective, secretory, absorptive
- submucosa - with/without glands
- muscle layers
- serosa - 7Give 3 requirements of the oesophagus1 - protection from abrasion
2 - muscle for propulsion
3 - lubrication - 8What species have a high degree of keratinisaed epithelium in oesphagusruminants and horse
- 9What are the 3 requirements of the small intestine- secretion of digestive enzymes
- absorptive surface
- muscle layers - 10Give the hierarchy of regulation in gastrointestinal functionautonomous activity
local - intrinsic - reflexes = neural and neuroendocrine
long reflexes - 11Describe the properties of gastrointestinal smooth muscle- forms syncytium - cells connected structurally and electrically
- connected by desmosomes and gap junctions
- electrical - activity generated in 1 cell and propagated to neighbouring cells
= synchronous contraction - 12Describe the membrane potential across smooth muscle- fluctuates across smooth muscle cells
- movement of sodium and calcium across membrane
- when membrane potential reaches threshold = CONTRACTION - 13What factors can modulate the threshold for contractionmechanical, neural, hormonal
- 14What is the resting tone of smooth musclemodulated by degree to which the muscle is stretched
- 15What are pacemaker cells- exhibit autonomous fluctuations in resting membrane potential
- initiate action potentials conducted throughout functional unit - 16What 4 factors affect the autonomous activity of gastrointestinal smooth muscle1 - receptors in gut wall
2 - intrinsic nerve plexuses - short reflexes, ENS
3 - locally produced gut hormones - enterogastrones
4 - extrinsic nerves - 17How do receptors in gut wall affect autonomous activitystretch and changes in chyme quality in gut lumen detected by various receptors on mucosal surface
- 18What is the intrinsic nerve plexuses made up ofsubmucosal plexus (in submucosa) and myenteric plexus (located between circular and longitudinal layers)
- 19What 3 things are found in the ENS- plexuses contain sensory nerves, interneurones, excitatory/inhibitory efferent neurons = ENS
- 20What 3 types of receptors are found in gut wall1 - chemoreceptors - sense pH, protein, fat levels
2 - mechanoreceptors - sense stretch, particulate matter
3 - osmoreceptors - sense osmolality - 21What are the properties of enterogastrones- local gut hormones that modulate motility and secretion
- produced by enterochromaffin cells in gut wall
- carried in blood stream to act in same/other regions of gut
- released in response to local changes in lumen
- modulated by intrinsic and extrinsic nerve pathways - 22What is the enterogastric reflex- changes in gastric secretion and motility are modulated in response to changes detected in chyme entering duodenum
- 23What are the properties of extrinsic nerve pathways and long reflexes- extrinsic nerves originate outside gut
- either sympathetic (inhibitory) or parasym (excitatory) nerves
- influence motility and secretion - 24What 3 ways do extrinsic nerves influence motility and secretion-modulating activity of intrinsic nerves
-stimulating release of enterogastrones
-acting directly on muscle/glands - 25What are the contractile patterns in gastric motility- receptive relaxation associated with gastric filling when large meal is eaten
- mixing
- grinding
- regulated emptying of chyme in duodenum - 26Give 2 reasons why gastric filling is not associated with proportionate increase in intralumen pressure1 - greater plasticity in smooth muscle -> structural arrangement of muscle fibres
2 - ingestion stimulates a vagally mediated relaxation of gastric smooth muscle to accommodate increased filling - 27How is storage and mixing achieved- pacemaker activity initiated in upper fundus
- waves of depolarisation sweep towards pylorus
- thicker muscle layers of pylorus allow for grinding of ingesta into small particles - 28How is the pyloric antrum adapted to gastric mixing- thicker muscular layer
- responsible for mixing
- contraction of pyloric sphincter - keeps it closed
- retropulsion of particulate chyme ->fundus of stomach
- liquid chyme -> stomach - 29Describe the process of gastric emptying- increased pyloric astral peristaltic contraction leads to increased gastric emptying
- altered by duodenal and gastric factors
- chemical/physical properties of chyme - 30How is gastric emptying controlledstomach - stretch and fluidity of chyme = increased emptying
duodenum - fat, acid, hypertonicity, distension = decreased emptying - 31What is the role of gastrin and what is the stimuli for its release- stimulates increased gastric motility and emptying
- stomach distension
- presence of protein / a a in pyloric region - 32Give the 5 stimuli for release of intestinal entergastrones in duodenum1- distension
2 - low pH
3 - increased protein
4 - increased fat
5 - increased osmolality of duodenal chyme - 33What 3 factors stimulate decreased gastric motility and emptyingCCK, secretin and GIP
- 34What are the 3 forms of intestinal motility- segmentation - mixing of chyme and max contact with absorptive surfaces
- migrating motor complexes (mmc) - peristaltic waves that propel food
- giant peristaltic contractions - longer duration and greater intensity than MMC
(distal SI, colon) - 35Where are the receptors that affect motility- enteric neurones
- gastrointestinal smooth muscle cells - 36What are the 2 main classes of drugs that are used to modify motility in the g gut and how do they workprokinetics - normalise motility
antispasmodics - reduce activity - 37What is the mechanism of action of spasmolytics- bind to receptors
- reduce gi tone and motility
- e.g. parasympathetic blocking agents (antagonists)
- blocks action of parasympathetic neurotransmitter ACh at receptor on smooth muscle cells - 38What is the mechanism of action of prokinetics- restore motility in injured gut after gastric distension
- more complex mechanism of action involving other neurotransmitters in ENS e.g. dopamine
- dopamine antagonists, cisapride
- increased ACh release in myenteric plexus
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- Veterinary bioscience - Digestive system Flashcards on Gastrointestinal motility, created by Teresa Richards on 15/03/2018.
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- Teresa Richards
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