Gastric Physiology and Motility - Prunuske Flashcards
When food enters the stomach, the fundal wall undergoes receptive relaxation as part of the swallowing reflex.
Which neurotransmitter(s) is(are) released during receptive relaxation?
ACh and NO/VIP
Expansion of the stomach signals forward to empty more distal segments.
Which reflexes explain why bathroom stalls are so full around lunch time?
Gastrocolic reflex - induces urge to defecate after meal ingestion
Gastroileal reflex - causes ileocecal valve to relax so contents are transferred from small to large bowel
What kind of substances can be absorbed by diffusion in the stomach?
Lipid soluble substances like alcohol or aspirin.
There is NO active transport
What enzyme releases peptides?
What enzyme produces free fatty acids
Peptides = pepsin
Free FAs = Gastric lipase
Remember mechanics important for emulsification
Low pH important for protein denaturation
How small must food be to leave the pylorus?
Smaller than 2mm!
Peristalsis occurs at the basic electrical rhythm of 3-5 per minute, originating in the pacemaker region of the gastric body. Parasympathetic stimulation causes the action potentials to occur.
The amplitude of the BER can be elevated in a couple ways, what are they?
Neural stimulation - ACh causes Ca influx
Hormonal - Increased gastrin
How will gastric emptying vary between foods?
Fats = slower
Protein = in between
Pure glucose= fast
List of mechanisms the stomach uses to empty fast:
- tonic fundus contraction
- deep peristalsis of body
- wide pylorus
- duodenal relax
- peristalsis of duodenum
List of mechanisms the stomach uses to delay emptying:
- Relaxation of fundus
- shallow body peristalsis
- shallow antral waves
- small pyloric opening
- duodenum does not relax, but doedo segmental contractions
The intestine can influence how fast the stomach empties. What intestinal stimuli will inhibit gastric emptying?
Acid in the duodenum
- via neural (enteric and vagal)
- Hormones (secretin/somatostatin)
Fat in the Duodenum
- Via neural (enteric)
- hormonal (CCK)
Osmolality of Duodenal contents
- neural (enteric)
- hormonal?
What is pyloric stenosis? How do you fix it?
Congenital condition. Pylorus fails to relax after a meal leading to malnutrition and dehydration.
Treat with surgical myotomy
What motility condition do you have to be worried about with diabetic neuropathy?
Gastroparesis
Reduced gastric emptying involving the vagus and enteric nerves in the stomach.
Causes nausea, bloating, vomiting, indigestion, weight loss, malnutrition, impaired med absorption, impaired glycemic control
How do you treat gastroparesis?
Prokinetic drugs!
Describe dumping syndrome.
Clinical symptoms?
Rapid gastric emptying often resulting from gastric bypass, vagotomy, and high sugar meals
Rapid entry of gastric contents into the lumen of duodenum causes lots of water to follow it in quickly. Results in low blood pressure and hypovolemia.
Clincal: Nausea, weakness, dizziness, sweating, shakiness, diarrhea, heart palpitations
List a few mechanisms in which emesis can be stimulated:
- Pharynx (gagging)
- Local irritants/bloodborne emetics
- Sensory (sight,smell)
- Vestibular system (inner ear)
- Gi tract blockage
All stimulate the emetic center in the medulla
Bloodborne emetics must contact the area postrema (spans BBB)
