Physiology Question Flashcards
What is the difference between dueodenocolic, enterogastric, intestine-intestinal, gastroileal and rectophincteric sreflexes?
1) duodenocolic
- result from distention of the stomach and duodenum which stimulates the colon to pass bowel movements
- gets suppressed when the extrinsic autonomic nerves in colon are removed
2) enterogastric
- occurs with intestine distention which results in inhibiting gastric motility and secretion
3) intestino-intestinal:
- occurs with distention or injury to a bowel segment which signals the bowel itself to relax
4) rectosphincteric:
- occurs when feces enters the rectum which stimulates the rectal sphincter to open to allow defications
5) gastroileal reflex:
- distention of the stomach causes relaxation of the ileocecal sphincter
Where are bile salts reabsorped?
Roughly 40% = throughout the small intestine by diffusion through mucosa
60% = active transport through the intestinal mucosa in the ileum specifically
Under basal (resting) conditions, which ions have the largest concentration in the saliva?
Potassium (2nd greatest overall and the highest when compared to plasma)
Bicarbonate (greatest overall)
Very low sodium and chloride ions at rest
What is the gastrointestinal hormone that is released in response to the big three macronutrients (fats/proteins/carbs)?
Glucose-dependent insulinotropic peptide (GLIP)
- primarily role is to mass release insulin and inhibit gastric acid secretion
- actually releases it the fastest and is why oral doses of glucose is metabolized quicker than IV glucose
What would a pressure tracing show like in a patient with achalasia?
There would be high esophageal pressure before and after swallow (would not change)
- dialated esophagus caused by failure of LES to relax
Under normal conditions, is sort of high, but not that high before swallowing and then decreases after swallowing to allow food through the LES and into the stomach
What are the primary causes of inhibited gastric acid secretion?
Somatostatin
Secretin
GLIP
Enterogastrones
Nervous reflexes
What is the only way to completely inhibit the cephalic phase of gastric secretion?
Vagotomy (removal/knock out of vagus nerve)
What are myoelectric complexes (MMCs)?
Peristaltic waves that contract every 90 minutes or so.
- slowly begin in the stomach and migrate through the entire stomach, small intestine and colon
- used to ensure all remaining undigested for residue is swept through stomach/small intestine and colon)
- also functions to maintain intestinal bacterial growth at acceptable levels
What factors go into deciding gastric emptying rates?
Tone of the orad of the stomach = directly proportional
Segmentation contractions in small intestines = inversely proportional
Presence of secretin/CCK and motilin = inversely proportional
Tone of the pyloric sphincter = inversely proportional
How does the cholera toxin work on epithelium of enterocytes?
Irreversibly increases cAMP levels
- results in irreversible opening of Chloride channels and cause mass movement of water and sodium into lumen = water diarrhea
What is the only gastrointestinal hormone to decrease gastric emptying under normal physiological conditions?
CCK
What is the average frequency of smooth muscle contractions based on the site of the GI tract?
note that the frequency of slow waves are fixed and cannot be changed
Stomach = 3 per minute
Duodenum = 12 per minute
Jejunum = 10 per min
Ileum = 8 per min
What is pentagastrin?
A synthetic gastrin compound
- literally mimics gastrin
What levels of gastrin are diagnostic for gastrinoma (zollinger-Ellison syndrome)?
Any serum concentrations greater than 110 pg/ml above baseline after administration of human secretin
- or >700 pg/ml at anytime
What is the role of enterokinase?
Cleaves trypsinogen -> trypsin/chymotrypsin
