Exam 4 - Pathophysiology of GI Disorders Flashcards by Cassie Kellogg

What are the different phases of digestion

Cephalic
Gastric
Intestinal

(CGI)

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Cephalic phase

Gastric acid secretion in response to stimuli

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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

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Stimuli are sent to the hypothalamus, prompting the ____ nerve to release ____

Vagus
Acetylcholine

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What receptor does acetylcholine bind to on stomach parietal cells? What does it cause them to produce?

Muscarinic receptors
HCl

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When does the gastric phase occur

When food enters to stomach to stimulate HCl

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What is distention?

Aka bloating

Occurs when food fills the stomach

Acetylcholine release is activated to stimulate HCl production in parietal cells

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What stimulates ECL cells to make histamine? This induces parietal cells to make ____ via ____

Gastrin

Make HCl via H+/K+ ATPase

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____ is pumped out of parietal cell via H+/K+ ATPase

H+

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____ follows H+ out of parietal cell into the stomach = HCl

Cl-

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Intestinal phase

Stage where duodenum responds to arriving stomach-processed food (chyme)

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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

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What form are most fats in the human diet?

Triglycerides

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What enzyme digests globules of fats

Lipases

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Orlistat MOA

Inhibits hydrolysis of triglycerides into fatty acids in the intestine, decreasing fat absorption

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What drug is a reversible inhibitor of GI lipases for weight loss?

Orlistat (Alli)

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Low-density lipoproteins (LDL)

Adds cholesterol to plaques, narrowing arterial blood flow

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____ and ____ are insoluble in water and are transported to tissues by lipoproteins

Triglycerides
Cholesterol

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High-density lipoproteins (HDL)

Carries excess cholesterol/LDL in blood and plaques to liver for elimination

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2 things used in carbohydrate metabolism

Sugars
Lactose

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Lactose intolerance

Problem w/ carbohydrate digestion that is due to reduction of lactase activity in adults

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In this deficiency, non-digested lactose is not absorbed

Lactase deficiency

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Lactose intolerance causes water to be retained in the ____, which causes ____

Retained in lumen

Causes cramps, nausea, diarrhea

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What further exacerbates lactose intolerance symptoms of gas?

Fermentation of lactose to lactic acid and CO2 by intestinal bacteria

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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

Exam 4 - Pathophysiology of GI Disorders Flashcards

(115 cards)