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METABOLISM > Gastrointestinal Motility > Flashcards

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?

Vagus nerve


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


What executes defecation?

Sphincter relaxation and rectal propulsive contractions