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48 Cards in this Set
- Front
- Back
Major functions of GI system (5)
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Motility
Secretion -synthesis and release of products Digestion - dietary constituents into molecules Absorption Elimination |
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GI role in immunity
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protect against microbial pathogen and permits immunologic tolerance of diet and helpful enteric microbes
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Enterogastric NS plexuses (2)
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Myenteric and Submucosal - execute gut motor activity in response to sensory input
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Enteric motor neuronal innervation
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Smooth muscle - exhitatory or inhibitory
Blood vessels - vasodilation Epithelial cells - H20, electrolyte secretion Glandular cells - secretion Endocrine cells - hormone secretion |
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Enteric reflex circuits - produced stereotyped responses when?
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Both fasting and fed states
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What 3 types of receptors are included in enteric sensory neurons?
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Mechanoreceptors
Chemoreceptors Thermoreceptors |
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What is the effect of ACh on enteric NS?
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Smooth musc cx, salivary gland, stomach, and pancreatic secretion
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What is effect of NE on enteric NS?
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Inhibits sm m cx, stimulate salivary secretions, cx of some sphincters
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Effect of VIP (vasoactive intestinal peptide) on ENS?
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Inhibits sm. m cx, stimulates pancreas/intestinal secretions
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Effect of GRH (Gastrin releasing hormone) on ENS?
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Stimulates G cells of stomach to release Gastrin
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What is the effect of enkephalins (endorphins) on ENS?
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Sm m cx but not peristalsis, inhibit intestinal secretion
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Effect of neuropeptide Y on ENS?
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Inhibitory, decreased secretion of water and electrolytes, decreased sm m cx
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Substance P
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Stim sm m cx
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Serotonin
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Excitatory in neuro-neuronal tx
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Gastrin, from G cells of stomach, does what?
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Stimulates gastric mobility but inhibits emptying, increases HCl secretion, stimulates mucosal growth
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CCK, from the I cells of duodenum, does what?
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Inhibits gastric emptying, stim gb cx, stim pancreatic enzyme secretion/growth of pancreas, potentiates secretin
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Secretin, from the S cells of duodenum, does what?
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Inhibits gastric emptying and HCl secretion, stim pancreastic/liver secretion of HCO3-, potentiates CCK
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GIP (gastric inhibitory peptide), from the duodenum/jejunum, does what?
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stim insulin secretion, inhibits gastric emptying and HCl secretion
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Motilin, from D&J, does what?
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In fasting state -> interdigestive migrating motor complex
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Intersitital cells of Cajal
where are they found what do they do |
Found primarily in myenteric plexus
Act as pacemaker, smooth waves hypopolarize sm m |
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Autonomic components of enteric NS?
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Sympathetic
Parasympathetic Nanadrenergic, noncholinergic |
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Vagovagal pathway - stimulus and effects
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Gastric distention induces receptive relaxation of fundus, increased HCl and gastrin secretion,
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Gastroileal pathway - stimulus and effects
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Gastric distention induces ileum motility and ileocecal sphincter relaxation
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Gastrocolic pathway - stimulus and effects
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Gastric distention induces colic motility
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Enterogastric reflex - stimulus and effects
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Acid, fat, or protein in duodenum inhibits gastric emptying
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Ileogastric reflex - stimulus and effects
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Distention of ileum inhibits gastric emptying
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Intestinointestinal reflex - stimulus and effects
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Distention of intestines inhibits motility below site of distention
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Why do we chew our food?
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Reduce food size, facilitate mixing of saliva with food to begin digestion, enhance sense of taste
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5 stages of oropharyngeal swallowing
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Elevation of tongue
Closure of nasopharynx Relaxation of UES Closure of glottis Pharyngeal peristalsis |
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How do primary and secondary peristalsis differ?
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Primary peristalsis occurs after pharyngeal cx when LES is relaxed
Secondary peristalsis occurs in response to esophageal distention |
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Lower esophageal sphincter innervation
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PNS - ACh binds M3 -> cx
Sympathetic - NE binds alpha, triggering Ach release and increased tone |
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Heartburn and LES tone
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Decreased LES tone causes GERD
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Achalasia and LES tone
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Inability of LES to relax causes achalasia
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Describe receptive relaxation of the stomach
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Occurs with every swallow
Vagovagal reflex |
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Describe accommodation of stomach
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Prevents increased gastric pressure
Vagovagal refex Longterm (fundal cx are independent of gastric slow waves) |
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Describe characteristics of gastric slow waves
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Initiated by ICC in body of stomach, triphasic
Strength and duration of cx depends on amplitude of slow waves |
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Why is retropulsive flow necessary?
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Caused by contractile wave hitting closed antrum and bouncing back, sheering reduces food particle size
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What is the relationship of osmolarity to emptying of stomach?
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Hyper/hypoosmotic fluids slow emptying
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Acid in duodenum and emptying of stomach
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Enterogastric reflex - slows emptying of stomach
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Calories and gastric emptying
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More calories, slower emptying
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Particle size and gastric emptying
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Particles > 1 mm not emptied. Large particle size inhibits empyting
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What are brush cells and where are they found?
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Chemosensory cells in the duodenum that mediate responses to stimuli
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Consequences of delayed gastric emptying
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Nausea, vomiting, bloating, epigastric pain, heartburn, wt loss
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Consequences of rapid gastric emptying
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anxiety, dizziness, tachycardia, sweating
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Fasting MMC complexes
Phase I |
Quiescent period 45-60 min
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Fasting MMC complexes
Phase II |
30-45 min, intermittent contractions
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Fasting MMC complex
Phase III |
5-10 min, cx with each slow wave, concentration of motilin increases prior to this phase
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Absence of MMC poses what risks?
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bacterial overgrowth in antrum and small intestine
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