Exam 4 - Pathophysiology of GI Disorders Flashcards
What are the different phases of digestion
Cephalic
Gastric
Intestinal
(CGI)
Cephalic phase
Gastric acid secretion in response to stimuli
Vagal nerve stimulation also induces cells to secrete histamine and HCl. What are these cells and which ones produce histamine vs HCl?
ECL cells secrete histamine
Parietal cells secrete HCl
Stimuli are sent to the hypothalamus, prompting the ____ nerve to release ____
Vagus
Acetylcholine
What receptor does acetylcholine bind to on stomach parietal cells? What does it cause them to produce?
Muscarinic receptors
HCl
When does the gastric phase occur
When food enters to stomach to stimulate HCl
What is distention?
Aka bloating
Occurs when food fills the stomach
Acetylcholine release is activated to stimulate HCl production in parietal cells
What stimulates ECL cells to make histamine? This induces parietal cells to make ____ via ____
Gastrin
Make HCl via H+/K+ ATPase
____ is pumped out of parietal cell via H+/K+ ATPase
H+
____ follows H+ out of parietal cell into the stomach = HCl
Cl-
Intestinal phase
Stage where duodenum responds to arriving stomach-processed food (chyme)
What are the 2 steps of protein metabolism
ACh stimulates stomach chief cells to secrete pepsinogen
Pepsinogen is converted to pepsin by HCl to digest protein
What form are most fats in the human diet?
Triglycerides
What enzyme digests globules of fats
Lipases
Orlistat MOA
Inhibits hydrolysis of triglycerides into fatty acids in the intestine, decreasing fat absorption
What drug is a reversible inhibitor of GI lipases for weight loss?
Orlistat (Alli)
Low-density lipoproteins (LDL)
Adds cholesterol to plaques, narrowing arterial blood flow
____ and ____ are insoluble in water and are transported to tissues by lipoproteins
Triglycerides
Cholesterol
High-density lipoproteins (HDL)
Carries excess cholesterol/LDL in blood and plaques to liver for elimination
2 things used in carbohydrate metabolism
Sugars
Lactose
Lactose intolerance
Problem w/ carbohydrate digestion that is due to reduction of lactase activity in adults
In this deficiency, non-digested lactose is not absorbed
Lactase deficiency
Lactose intolerance causes water to be retained in the ____, which causes ____
Retained in lumen
Causes cramps, nausea, diarrhea
What further exacerbates lactose intolerance symptoms of gas?
Fermentation of lactose to lactic acid and CO2 by intestinal bacteria
Fibers are large in ____
Carbs that the body cannot digest
What are fiber supplements used for in self-care
Constipation
What do bulking fibers (ex. Cellulose, psyllium) absorb
Water
How do fiber supplements aid in constipation?
By increasing the amount of water in the stool, making it easier to pass
What types of GI disorders are associated w/ abdominal or chest pain?
Heartburn
Esophageal reflux
GERD
What is anorexia?
Lack of appetite
What is dysphagia?
Difficulty swallowing
What is odynophagia?
Painful swallowing
What symptoms are associated with altered digestion of food?
Nausea/vomiting
Dysphagia
Odynophagia
Anorexia
Heartburn is associated with what major symptom?
Weakened lower esophageal sphincter (LES) pressure
Etiology of heartburn
Stomach acid exposure to esophageal mucosa
LES normally is contracted at rest (increase pressure) and relaxes (decrease pressure) on swallowing to permit flow of food into stomach
Increased rate of spontaneous relaxations or impaired reflexes of LES enable stomach acid to move into esophagus, causing inflammation
Gastroesophageal reflux disease (GERD)
Frequent heartburn
What can GERD cause?
Chronic inflammation
Less commonly: erosion of esophageal mucosa
NERD
Non-erosive GERD form
Any impaired digestion is termed ___
Dyspepsia (indigestion)
What is nausea?
Pronounced stomach discomfort
A precursor to forceful evacuation of stomach contents
What is the “vomiting center” in the brain within the medulla?
Brainstem
What is another name for vomiting?
Emesis
What receptors activate the vomiting center?
Muscarinic (ACh)
Chemoreceptor trigger zone (CTZ)
Located adjacent to the vomiting center
Stimulated by chemical toxins in the blood
CTZ activation of the vomiting center is also involved in ____
Motion sickness
(Think antiemetics)
CTZ is also stimulated by the activation of ____
Surface 5-HT3 (serotonin)
What does the activation of CTZ by blood toxins stimulate? What does this induce?
Stimulates muscarinic receptors on the vomiting center
Induces vomiting reflex
What does labyrinth hyperstimulation activate
Vestibular nuclei
Where is the vestibular center
In the inner ear in the labyrinth
What is used to treat motion sickness?
H1 antagonists
Examples of H1 antagonists
Meclizine
Diphenhydramine
What can also be directly stimulated by sensory stimuli and emotion?
Vomiting center
(Certain feelings make me nauseous because of my sensory issues and anxiety puking is common)
Enterochromaffin cells
Cells lining the stomach that release serotonin in response to cytotoxic agents when damaged
Vomiting reflex can be provoked by the ingestion of ___
Toxins
Symptoms of diarrhea
Increased stool frequency and volume
Serotonin stimulates 5-HT3 receptors found on the ___
Vagus nerve
What is acute diarrhea usually due to?
An infectious cause (e coli, rotavirus)
Constipation
Difficult/infrequent passage of stool
Constipation may be associated with…
Straining or incomplete defecation
What happens if the stool remains in the colon?
It becomes drier, making it harder to pass through the anal canal
What are hemorrhoids?
Swollen veins in the lowest part of the rectum/anus where blood vessels stretch to the point where they bulge and become irritated during defecation
_____ in the hemorrhoid can cause severe pain
Clot formation
How are hemorrhoids formed?
Straining during bowel movements
Common antacids
Mylanta/maalox
Tums/rolaids
Pepto-bismol
Alka-seltzer
Common H1 blockers (antiemetics)
Diphenhydramine
Meclizine
Common H2 blockers
Famotidine
Cimetidine
Nizatidine
Common PPIs
Omeprazole
Lansoprazole
Esomeprazole
Common antiflatulent agents
Simethicone
Beano
Activated charcoal
Lactase
Common antimotility agents
Loperamide
How do antacids work?
Weak bases neutralize gastric HCl to form a salt and water
Neutralization also blocks conversion of
Pepsinogen to pepsin
Sodium bicarbonate (alkaseltzer)
Reacts rapidly w/ HCl to produce increased CO2 (cause belching) and NaCl (fluid retention)
Calcium carbonate
Less soluble and reacts more slowly than sodium bicarb w/ HCl to form increased CO2 and CaCl2
Magnesium hydroxide
Milk of magnesia and aluminum hydroxide combo product
Reacts w/ HCl to form H2O plus MgCl2 & AlCl3
No gas generation =
No belching
What may unabsorbed Mg2+ salts cause?
Osmotic diarrhea
What may unabsorbed Al3+ salts cause?
Constipation
What are H2 antagonists
Competitive inhibitors (w/ histamine) at the parietal cell H2 receptor
___ released from ECL cells is blocked from binding to _____
Histamine
Parietal cell H2 receptor
H2 antagonists in order of potency
Famotidine
Nizatidine
Cimetidine
(FNC sounds like DNC so that order makes sense)
What drug class inhibits the gastric parietal cell proton pump, an H+/K+ ATPase
PPIs
Prodrugs that are activated in an acidic environment, binding covalently w/ -SH groups on cysteine residues on H+/K+ ATPase
PPIs
Pump inactivate is _____. What does this mean?
Irreversible
Acid secretion resumes only after new pump molecules are synthesized
What type of formulations are used for PPIs
Delayed release
On oral intake, PPI prodrugs must reach the _____
Bloodstream
____ formulations are used to ensure passage to the intestines
Delayed release
Nonprescription PPIs
Omeprazole
Esomeprazole
Lansoprazole
What drug class is for the treatment of gas?
Antiflatuent
Antiflatuent agent MOA
Decrease gas formation or aid in its elimination
Defoaming agent
Merges small gas bubbles into a larger one to be eliminated more easily by belching or passing flatus
Activated charcoal
Absorbs gas and reduces odor
Alpha-galactosidase
Enzyme that breaks down complex carbs (fiber) before bacteria ferments it in the colon
Lactase replacement
Enzyme that breaks down lactose before bacteria ferments it in the colon
What is the primary ingredient in Gas-X and Mylanta Gas?
Simethicone
What is the primary ingredient in Beano?
Alpha-galactosidase
What is the primary ingredient in Lactaid and Lactase
Lactase enzyme
Antidiarrheal agents include:
Bismuth subsalicylate (pepto)
What causes the anti-secretory effects of antidiarrheals?
Prostaglandin inhibition and stimulation of Na+/Cl- absorption
How to opioid antimotility agents work?
Slowing chyme passage, enabling water and electrolyte absorption to firm up stool
Characteristics of opioid antimotility agents
Binds to Mu opioid receptors in intestines
Inhibits ACh release, causing paralysis of GI motility
Relieves diarrhea through decreased GI motility
What antimotility agent for diarrhea is poorly absorbed and excreted in the feces (no euphoria)
Loperamide
____ are used for the treatment of constipation
Laxatives
Stimulants
Act to increase intestinal peristalsis
Ex. castor oil, senna, bisacodyl
Bulking laxatives
Absorb water stimulating peristalsis
Ex. Methylcellulose, fibercon, metamucil
Hyperosmotic agents
Draw water into the intestine via osmosis, increasing intestinal motility
Ex. Miralax
Saline laxatives
Increase intraluminal pressure & intestinal motility (milk of magnesia)
Emollients
Anionic surfants that become emulsified w/ stool, thereby softening it
Ex. Docusate
Lubricants
Mineral oil softens feces by coating stool and prevents stool drying due to intestinal water absorption
Motion sickness stimulates the vomiting center via _____
Vestibular nucleus
What will impair the signaling to the vomiting center?
Inhibition of H1 chemoreceptors in the vestibular nucleus
____ are used to relieve the nausea and vomiting symptoms of motion sickness due to hyperstimulated labyrinthine function
H1 antagonists (antihistamines)
8-cholorotheophylline salt of diphenhydramine
Dramamine
What is added to counteract the sedation effects of diphenhydramine?
Chlorotheophylline
Antimimetic agents
Dramamine
Meclizine
What else can motion sickness symptoms associated w/ the stomach be treated with? What does it contain?
Phosphorated carbohydrate solution
Contains: glucose, fructose, phosphoric acid
