Gastrointestinal Flashcards
What are the layers of the intestinal wall?
○ serosa
○ longitudinal muscle layer
○ circular smooth muscle layer
○ submucosa
○ mucosa
Slow waves in the gastrointestinal smooth muscle are caused by which cell acting as a pacemaker
Interstitial cells of Cajal
What are slow waves in the gastrointestinal smooth muscle
rhythmic, undulating changes in resting membrane potential
What are spike potentials in gastrointestinal smooth muscle
True action potentials which occur when membrane potential exceeds -40mv
Entry of what ion into the smooth GI muscle causes contraction (action potential)
Calcium
What are the two major plexuses of the enteric autonomic nervous system
Myenteric plexus: between longitudinal and circular muscle layers
Submucosal plexus: in the submucosa
What are the functions of the myenteric and submucosal plexus
Myenteric - controls muscle activity along the length of the gut (contraction rate and rhythm)
Submucosal - controls function in each segment of intestine (local hormonal secretion, local muscle contraction)
What is the effect of these neurotransmitters on gastrointestinal activity:
Norepinephrine (SNS)
Acetylcholine (PSNS)
Acetylcholine: mostly excites gastrointestinal activity
Norepinephrine: almost always inhibits gastrointestinal activity
Gastrin:
- Stimuli for secretion:
- Site of secretion
- Actions:
- Stimuli for secretion: proteins, distension, nervous stimulation
- Site of secretion: G cells in antrum, duodenum and jejunum
- Actions: Stimulates gastric acid secretion and mucosal growth
Cholecystokinin (CCK)
- Stimuli for secretion:
- Site of secretion
- Actions:
- Stimuli for secretion: Proteins, fats and acid
- Site of secretion: I cells of duodenum, jejunum, ileum
- Actions:
- Stimulates pancreatic enzyme secretion, pancreatic bicarbonate secretion, gallbladder contraction,
- Inhibits gastric emptying
Secretin:
- Stimuli for secretion:
- Site of secretion
- Actions:
- Stimuli for secretion: Acid and fat
- Site of secretion: S cells of duodenum, jejunum, ileum
- Actions:
- Stimulates pepsin secretion, pancreatic bicarbonate secretion, biliary bicarbonate secretion,
- Inhibits gastrin release and gastric acid secretion
Gastric inhibitory peptide (GIP)
- Stimuli for secretion:
- Site of secretion
- Actions:
- Stimuli for secretion: Protein, Fat, Carbohydrate
- Site of secretion: K cells of duodenum and jejunum
- Actions:
- Stimulates insulin release;
- Inhibits gastric acid secretion
Motilin
- Stimuli for secretion:
- Site of secretion
- Actions:
- Stimuli for secretion: Fat, Acid, Nervous
- Site of secretion M cells of duodenum and jejunum
- Actions: Stimulates gastric motility and intestinal motility
Pepsinogen
- Stimuli for secretion:
- Site of secretion
- Actions:
- Stimuli for secretion: ACH from vagus nerves/enteric plexus and stomach acid
- Site of secretion: Peptic (chief cells) in gastric mucosa secrete pepsinogen
- Actions:
When activated by HCL causes proteolysis
What do the parietal (oxyntic) cells secrete
HCl and intrinsic factor
What do the enterochromaffin-like (ECL) cells secrete
Histamine
What hormones are involved in gastric acid secretion
Histamine, Gastrin and Pepsinogen
