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Description
Flashcards by Evian Chai, updated more than 1 year ago
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Created by Evian Chai
over 4 years ago
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| Question | Answer |
| What muscles are involved in gut motility? | Mainly smooth, but skeletal at critical points |
| What innervates the gut and what is it stimulated by? | Enteric nervous system Regulated by ANS but somatic neurones affect key areas (eg. oesophagus) |
| How are nerves in the gut stimulated? | With hormones released by cells |
| What is the function of sphincters/valves? | Ensure correct timing and one way traffic |
| What 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) |
| What do interneurons do? | Many kinds, for reflexes |
| What types of sensory neurones are present? | 1. Chemosensitive (for H+/pH) 2. Mechanoreceptors (for distension) |
| What does the upper/lower oesophageal sphincter do? | Allows swallowing, prevents reflux |
| What does the pyloric sphincter do? | At the base of stomach, so controls exit of food to duodenum |
| What does the Ileo-caecal sphincter do? | Controls movement from Ileum to colon |
| What do the anal sphincters do? | Control defecation |
| What 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 |
| How 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 |
| What is peristalsis? | Wave like contractions for moving food down gut |
| Why 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 |
| What 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 |
| What 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 |
| What is chyme? | pulpy acidic fluid which passes from the stomach to the small intestine, consisting of gastric juices and partly digested food |
| What nervous system controls gastric emptying? | the ANS (increased SNS/decreased PNS) |
| What 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 |
| What is the main motility in the small intestine? | Segmentation as contraction of different parts lead to mixing |
| What makes the ileo-caecal sphincter contract? | Downstream pressure/SNS |
| What 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 |
| Is the internal or external anal sphincter involuntary (PNS?) | The internal The external is voluntary |
| Which muscles controlled by the PNS are activated when you defecate? | Rectal circular muscle contracts Internal anal sphincter relaxes |
| Which muscles controlled voluntarily are activated during defection? | External anal sphincter relaxes Levator ani contracts |
| How does the PNS/SNS impact gut motility? | Increased PNS increases Increased SNS decreases |
| How 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 |
| How does the hormone Gastrin affect gut motility? | It increases gastric motility when digesting a meal (initial) |
| How does the hormone CCK affect gut motility? | Decreases gut motility in response to increased fats |
| How do the hormones GIP/GLP-P affect gut motility? | Lowers gut motility in response to sugars Also increases insulin from pancreas |
| What external factors impact gut motility? | 1. Diet composition -H20 retention, microbiota in gut 2. Medication 3. Age as ENS neurones degenerate |
| What are 5 issues related to gut motility? | 1. Acid reflux 2. Malabsorption 3. Bacterial overgrowth 4. Diarrhoea 5. Constipation |
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