Flashcards
BMS13-1055 Mechanisms of Gastrointestinal Motility and its control
Cards in this deck (33)
- 1What muscles are involved in gut motility?Mainly smooth, but skeletal at critical points
- 2What innervates the gut and what is it stimulated by?Enteric nervous system
Regulated by ANS but somatic neurones affect key areas (eg. oesophagus) - 3How are nerves in the gut stimulated?With hormones released by cells
- 4What is the function of sphincters/valves?Ensure correct timing and one way traffic
- 5What 4 areas do motor neurones innervate?1. Smooth muscle (both excitatory and inhibitory)
2. Vasomotor (intrinsic arterioles)
3. Secretomotor (cells regulating acid secretion)
4. Epithelium (enteroendocrine cells) - 6What do interneurons do?Many kinds, for reflexes
- 7What types of sensory neurones are present?1. Chemosensitive (for H+/pH)
2. Mechanoreceptors (for distension) - 8What does the upper/lower oesophageal sphincter do?Allows swallowing, prevents reflux
- 9What does the pyloric sphincter do?At the base of stomach, so controls exit of food to duodenum
- 10What does the Ileo-caecal sphincter do?Controls movement from Ileum to colon
- 11What do the anal sphincters do?Control defecation
- 12What are the three phases of swallowing, and what occurs in each?1. Oral phase
- tongue pushes bolus to back of mouth to trigger swallow
2. Pharyngeal phase
- upper oesophagus sphincter relaxes
- epiglottis closes to protect airway
3. Oesophageal phase
- bolus moves down into oesophagus w aid of peristalsis and gravity - 13How does the muscle type and innervation of the oesophagus change as you go down?Upper 1/3: brainstem motor neurones, somatic motor neurones to striated muscle
Overlap zone: both
Lower 1/3: vagus nerve of ANS innervates smooth muscle - 14What is peristalsis?Wave like contractions for moving food down gut
- 15Why does the oesophagus enter the stomach at an angle?So intergastric pressure squashes a wall and closes a valve like flap to achieve one way traffic
- 16What occurs when food enters the stomach?1. Internal ruguae flatten
2. Muscle wall relaxes via receptive relaxation by PNS/brainstem
3. Stomach wall contracts to mix contents and propel to pyloric region - 17What controls stomach contractions, and how do they change as you approach the pyloric region?Pacemaker cells send contractile waves
Waves get stronger to increase pressure so chyme can pass through narrow sphincter - 18What is chyme?pulpy acidic fluid which passes from the stomach to the small intestine, consisting of gastric juices and partly digested food
- 19What nervous system controls gastric emptying?the ANS (increased SNS/decreased PNS)
- 20What is the feedback relationship between gastric emptying and the duodenum?Negative feedback
Increased acidity/fat/AA/hypotonicity/distension increase secretion of enterogastrones
Enteric neurons stimulated to decrease gastric emptying - 21What is the main motility in the small intestine?Segmentation as contraction of different parts lead to mixing
- 22What makes the ileo-caecal sphincter contract?Downstream pressure/SNS
- 23What are the two types of movement in the large intestine?1. Haustrations: short segments where circular/longitudinal muscles contract to mix food
2. Mass movement: longer segments of circular muscle contract for bulk movement - 24Is the internal or external anal sphincter involuntary (PNS?)The internal
The external is voluntary - 25Which muscles controlled by the PNS are activated when you defecate?Rectal circular muscle contracts
Internal anal sphincter relaxes - 26Which muscles controlled voluntarily are activated during defection?External anal sphincter relaxes
Levator ani contracts - 27How does the PNS/SNS impact gut motility?Increased PNS increases
Increased SNS decreases - 28How does the hormone Motilin affect gut motility? Where is it released?It regulates background motility in between meals by causing SM contractions in upper small intestine
Released from scattered cells in epithelium - 29How does the hormone Gastrin affect gut motility?It increases gastric motility when digesting a meal (initial)
- 30How does the hormone CCK affect gut motility?Decreases gut motility in response to increased fats
- 31How do the hormones GIP/GLP-P affect gut motility?Lowers gut motility in response to sugars
Also increases insulin from pancreas - 32What external factors impact gut motility?1. Diet composition
-H20 retention, microbiota in gut
2. Medication
3. Age as ENS neurones degenerate - 33What are 5 issues related to gut motility?1. Acid reflux
2. Malabsorption
3. Bacterial overgrowth
4. Diarrhoea
5. Constipation
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- Description
- mechanism and role of saliva production • how parietal (oxyntic) cells of the stomach secrete HCl and regulating factors • other gastric secretions (pepsinogen, mucus, intrinsic factor, gastric lipase) and their regulation • the factors which govern the rates of secretion of gastrin, CCK/PZ, and secretin • source and roles of GLP-1 & GIP • main secretions of small intestine enterocytes exocrine secretions of the pancreas (composition, source, stimuli) bile formation dysfunctions
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- Evian Chai
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