Flashcards in Gastrointestinal Motility Deck (19):
What are the 3 phases of the body's response to food?
Cephalic, gastric and intestinal
Describe the cephalic phase of food exposure
Though, sight, smell and taste work to prepare GI tract through saliva, gastric acid and pancreatic secretion as well as inhibition of migrating motor complexes, gastrin and ghrelin secretion
Describe the gastric phase of food exposure
Satiation and early digestion triggered by mechanical effect
Describe the intestinal phase of food exposure
Feedback and satiation triggered mainly by chemoreceptor activation in the small bowel
What happens during hunger in the GI tract?
There are there phases of contraction every 90-120 minutes which works to clear undigested material, prevent bacteria overgrowth and create hunger sensations
How does the initiation of migrating motor complexes differ between the stomach and the small intestine?
Stomach is vagus-dependent and the small intestine is vagus-independent
How does food move through the oesophagus?
Primary peristaltic wave occurs on swallowing due to contraction of striated muscle (vagus nerve), stretch receptors are then stimulated and a local reflex causes a secondary peristaltic wave which forces the bolus into the stomach as the LOS relaxes
What is involved in receptive relaxation?
The vago-vagal reflexes causes the release of CCK
What is involved in adaptive relaxation?
Enteric reflex releases NO from the ENS
What are interstitial cells of Cajal (ICCs)?
Cells around the myenteric plexus within stomach muscle and colon and around the submucosal plexus of the colon; they create rhythm of electrical slow waves to cause phasic muscle contractions
Name the three stages of gastric emptying
propulsion, emptying and retropulsion
Describe the process of gastric emptying
Propulsion: rapid flow of liquids into stomach, delays flow of large particles towards pylorus
Emptying: liquids with small molecules are passed into duodenum whereas large particles are retained in a bulge in the terminal antrum
Retropulsion: movement into the antrum enables powerful contractions to further breakdown the particles, then there is clearing of the terminal antru
What provides the extrinsic innervation of the gut?
What causes gas build-up in the stomach?
Swallowing air (during eating/drinking) or due to increased swallowing due to increased salivation
How is excess air released from the stomach?
LOS relaxes --> burp --> reduces stomach pressure --> avoids early satiety
Describe the role of enteric sensory neurones
Have mechanical and chemosensitive receptors which respond to an intraluminal signal --> information transmitted via interneurons to motor neurones which secrete NO and/or ACh and this initiates the peristaltic reflex and modulates immune, vascular, muscular and epithelial transport systems
What is defecation normally prevented by?
Tone of internal anal sphincter, puborectalis muscle and mechanical effects of acute anorectal angle
What initiates defecation?
Puborectalis muscle and external anal sphincter relax and intra-abdominal pressure is increased by squatting in preparation