GI 2 Flashcards
What are the 3 actions of the myenteric plexus?
- tone of gut wall
- rhythmic contraction
- rate of contraction
What are the pacemaker cells of the enteric nervous system?
interstitial cells of Cajal
The slow wave is potentiated by what channel?
sodium channels
the spike potentials are d/t what channel?
calcium channels
What factors increase excitability of the ENS?
- increased stretch/distension
- Parasympathetic Stimulation via Ach
What are the effects of the parasympathetic and sympathetic nervous system on motility?
- sympathetic = decreases motility
- parasympathetic = increases motility
What are the 3 prevertebral reflexes and what are their effects?
- gastrocolic = filling stomach causes defecation
- enterogastric = filling colon closes pyloric sphincter
- colonoileal = colon distention closes ileocecal valve
What is the effect of pain on GI motility?
pain decreases GI motility
What are the 2 suspected causes of IBS?
- anxiety/depression
- Post-infectious IBS (d/t acute gastroenteritis)
Where is the site of secretion of gastrin?
G cells (antrum of stomach)
Where is the site of secretion of CCK?
I cells (duodenum and jejunum)
Where is the site of secretion of secretin?
S cells (duodenum)
Where is the site of secretion of GIP?
K cells (duodenum and jejunum)
What are the 2 actions of gastrin?
- increase gastric acid secretion
- increase stomach muscle contraction rate/force
- increase growth of gastric mucosa
What are the 3 actions of CCK?
- inc gallbladder contraction –> eject bile
- relax sphincter of Oddi
- inc pancreatic enzymes & HCO3- secretion
- inc growth of exocrine pancreas
- inc small intestine contraction
result = bile ejection + slows gastric emptying
What is the action of secretin?
- blocks gastrin effects ->inhibit gastric contraction
- inc pancreatic and biliary HCO3- secretion
Which of the gastric hormones blocks gastrin effects?
secretin
What is the action of GIP & GLP-1?
- increase pancreatic insulin secretion*
- inhibit glucagon release
- blocks gastric acid secretion
- slows gastric emptying*
What stimulates gastrin secretion? (3)
- amino acids/protein peptides in antrum
- distention of stomach
-vagal stimulation
What stimulates CCK? (2)
-fats and fatty acids entering in small intestine
What stimulates secretin? (2)
- stomach distension
- protein products & fatty acids
- acid entering the duodenum
What stimulates GIP? (3)
- glucose
- amino acids
- fatty acids
What is the difference between primary and secondary peristalsis?
- primary = begins in pharynx and speeds down into esophagus
- secondary = initiated from distention sensed if food remains in peristalsis after primary peristalsis, consciously feel this peristalsis*
What ligament helps keep the LES closed?
phrenoesophageal ligament
What can occur if the phrenoesophageal ligament ruptures from increased abdominal pressure?
hiatal hernia
What is Zenker Diverticulum?
herniation of the esophageal mucosa posteriorly through muscles of esophagus
patient will complain of bad breath, regurgitation of solid foods
What is the vagovagal reflex?
as food stretches the stomach –> the muscles relax allowing for the pressure to remain low
Stomach emptying is mainly under the control of what?
- duodenal neurologic inhibitory control
- secretin has smaller effect, takes longer-
What 3 hormones increase small intestine motility?
- Gastrin
- CCK
- Insulin
What 2 hormones decrease small intestine motility?
- Secretin
- Glucagon
What is the difference in function between the proximal and distal large bowel?
- proximal = absorbs electrolytes/H2O
- distal = stores fecal matter
What 2 muscles allow for the mixing movement of the colon?
- teniae coli –> longitiduinal (shortens)
- circular muscle –> circular (constricts lumen)
The external anal sphincter is under voluntary control via this nerve.
pudendal nerve
What is the pathophysiology of adynamic ileus?
trauma causes a shift in autonomic balance which leads to impaired gut motility
How does diverticulosis occur?
dec bolus mass d/t lack of fibrin in diet causes straining of the large bowel to move small fecal matter through anus –> inc pressure within lumen –> outward herniations through penetrating arteries
What triggers the Duodenal Neurologic Inhibitory control of stomach emptying?
- distension of small intestine
- food products (fat and protein products)
- inc chyme acidity in duodenum
How does diverticulitis occur?
blockage of a penetrating artery –> creates an outpouch of fecal matter/tissue that becomes ischemic –> necrosis –> infection occur
The internal anal sphincter and external anal sphincter are composed of what types of muscle respectively??
Internal Anal Sphincter: smooth muscle
External Anal Sphincter: striated muscle
Large bowel motility is mainly which type of bowel movement?
- Propulsive movement of bowel
- No mixing occurs
The small intestine terminates at what structure that connects to the large intestine?
Ileocecal valve
Small intestine motility is comprised of what types of bowel movements (2)? Why are their importance?
1) Mainly mixing contractions
2) Very slow propulsive contractions
-ensures absorptions of nutrients in small intestine-
What are the 3 motor functions of the stomach?
- store food
- mix with gastric secretions
- control stomach emptying
What are the stages of swallowing?
Which phases are under voluntary vs autonomic control?
- Voluntary Stage -> move bolus w/ tongue to the hard palate
- Autonomic pharyngeal and esophageal stages –> transports food from pharynx through larynx and into the stomach
