Physiology Flashcards
unitary smooth muscle characteristics
- spontaneous contraction
- activated by stretch or distention
- found in stomach and intestine
multi-unit smooth muscle features
- requires direct neural or hormonal stimulation
- lacks spontaneous contraction
- found in esophagus and gallbladder
spike potentials
- generate contractile events
- increase in Ca leads to increased spike potentials and vice versa
submucosal (Meissner’s plexus)
- between circular muscle and submucosal layers
- functions largely in secretion
- only excitatory
myenteric (Auerbach’s plexus)
- between muscle layers
- regulates contraction
- excitatory and inhibitory
inhibitory NTs
- VIP and NO
excitatory NTs
- ACh and substance P
hormonal vasodilators
- CCK, VIP, gastrin, secretin, kinins, decreased oxygen levels leading to increased adenosine
action of gastrin
- increases gastric H secretion
- increases growth of gastric mucosa
- increases gastric motility
regulation of gastrin
- increased by stomach distention, akalinization, amino acids, peptides, vagal stimulation
- decreased by stomach pH <1.5
CCK action
- increases pancreatic secretion
- increases gallbladder contraction
- decreases gastric emptying
- increases sphincter of Oddi relaxation
CCK regulation
- increased by fatty acids and amino acids
action of secretin
- increases pancreatic HCO3
- decreased gastric acid secretion
- increases bile secretion
regulation of secretin
- increased by acid, fatty acids in lumen of duodenum
action of somatostatin
- decreases gastric acid and pepsinogen secretion
- decreased pancreatic and small intestinal fluid secretion
- decreases gallbladder contraction
- decreases insulin and glucagon secretion
regulation of somatostatin
- increased by acid
- decreased by vagal stimulation
VIP action
- increases intestinal water and electrolyte secretion
- increases relaxation of intestinal smooth muscle and sphincters
VIP regulation
- increased by distention and vagal stimulation
- decreased by adrenergic input
NO action
- increases smooth muscle relaxation, including LES
motilin action
- produces migrating motor complexes (MMCs)
motiln regulation
- increased in fasting state
three stages of swallowing
- voluntary
- pharyngeal
- esophageal
voluntary swallowing
- tongue pushes food towards back of the mouth
pharyngeal swallowing
- efferents sent through CNs (ACh)
- soft palate moves over nasopharynx
- trachea closes off
- UES relaxes
esophageal swallowing
- primary peristalsis is simply the continuation of the peristaltic wave that begins in the pharynx and spreads into the esophagus during the pharyngeal stage of swallowing
- secondary peristaltic waves result from distention of the esophagus itself by the retained food
delayed emptying: vagal neuropathy or DM
- gastroparesis
- delayed emptying of solids
MMC
- migrating myoelectric complexes
- electrical oscillations fire spike potentials leading to contractions
- motilin released at onset of MMC
- MMCs are terminated by ingesting food, CCK and gastrin
peristaltic rush
- longer waves of contraction brought on by irritation, excessive distention, extrinsic and intrinsic neural control
power propulsion (mass movements)
- programmed motor event of the ENS
- last 18-20 seconds
- cramping maybe associated
- occur about 15 minutes after a meal
- provoke the urge to defacate
hyperthryoidism
- increases GI motility and may result in diarrhea
hypothyroidism
- decreases GI motility and may result in constipation
function of mucins
- lubricate and protect
- creates a bolus
activators of HCl secretion
- histamine
- gastrin
- ACh
inhibitors of HCl secretion
- somatostatin
- prostaglandins
achlorhydria
- dysfunction of parietal cells caused by antibodies or use of PPIs
- results in increased susceptibility to infection, malabsorption and diarrhea
inhibitors of gastric acid secretion
- distention of small bowel
- acid in duodenum
- protein digestion products
- irritation
activators of chief cells
- neural: ACh, VIP
- hormonal: gastrin, CCK, secretin, GIP
