Gastrointestinal Pharmacology Quiz

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Questions and Answers

What condition is commonly associated with new onset constipation in patients over 50 years of age?

Irritable bowel syndrome

Malignancy risk (correct)

Diarrhea episodes

Pregnancy complications

What is the primary role of the large intestine?

Breakdown of proteins

Production of digestive enzymes

Absorption of nutrients

Conversion of chyme into faeces (correct)

Which of the following statements about motilin agonists is true?

They decrease gastric tone.

They can worsen symptoms despite improving gastric emptying. (correct)

They only enhance gastric emptying.

They promote gastric accommodation.

Which of the following structures in the colon is responsible for secreting mucus?

Goblet cells Signup and view all the answers

What is a characteristic feature of the colonic wall?

Formation of haustra due to shorter muscle bands Signup and view all the answers

What is the mechanism by which omeprazole inhibits gastric acid secretion?

It forms covalent disulfide bridges with cysteine residues Signup and view all the answers

What is the primary mechanism of action of Metoclopramide in the gastrointestinal tract?

It acts as a dopamine D2 antagonist and a serotonin 5-HT4 agonist. Signup and view all the answers

Which cells in the gastric glands secrete hydrochloric acid (HCl) and intrinsic factor?

Parietal cells Signup and view all the answers

What enzyme is responsible for the digestion of proteins in the stomach?

Pepsin Signup and view all the answers

What is the primary role of efferent pelvic impulses during defecation?

Cause reflex contraction of the rectum and relaxation of the internal anal sphincter Signup and view all the answers

What is a common effect of inhibiting the natural defecation reflex?

Greater likelihood of constipation Signup and view all the answers

Which factor is NOT commonly associated with the development of constipation?

Frequent bowel movements Signup and view all the answers

Which medication type is primarily used to treat constipation by increasing stool bulk?

Bulk-forming agents Signup and view all the answers

What is a potential risk when using magnesium-containing laxatives?

Risk of hypermagnesemia Signup and view all the answers

In context to diarrhea, which type is characterized by inflammation of the gastrointestinal epithelium?

Inflammatory diarrhea Signup and view all the answers

What symptom is typically NOT associated with inflammatory diarrhea?

Increased appetite Signup and view all the answers

Which of the following represents a possible complication of untreated faecal impaction?

Complete blockage of the colon Signup and view all the answers

What effect does stimulation of the pelvic nerves have on the colon?

Increases mucus secretion Signup and view all the answers

What role do bacterial infections play in bowel movement?

They stimulate mucus secretion for dilution Signup and view all the answers

How much water is typically absorbed in the large intestines per day?

About 0.5 - 1.5L Signup and view all the answers

What is the result of poor motility in the colon?

Hard feces formation and constipation Signup and view all the answers

What is actively absorbed by Na+-K+ ATPase in the colon?

Sodium Signup and view all the answers

What substance is exchanged for chloride absorption in the colon?

Bicarbonate Signup and view all the answers

What happens to bowel movements with excessive motility?

Decreased absorbance and loose feces Signup and view all the answers

What important vitamins are absorbed in the large intestine?

Vitamin K Signup and view all the answers

Study Notes

GI Conditions (of Concern)

Heartburn is a burning sensation in the chest due to stomach acid refluxing up into the throat. This is also known as Gastro-oesophageal reflux disease (GORD) if it occurs frequently.
Dyspepsia/Indigestion is an uncomfortable feeling in the stomach that can manifest as pain, indigestion, and nausea.
Gastritis is an inflammation of the stomach lining, causing pain and discomfort.
Nausea and Vomiting are common digestive issues that often accompany other problems.
Peptic Ulcer Disease involves ulcers in the stomach lining.
Constipation and Defecation Problems refer to difficulties with bowel movements, varying from infrequent stools to difficult passage.
Diarrhea involves frequent, loose stools.
Gastroparesis is a condition where the stomach cannot empty normally. Food moves through the stomach more slowly than usual, often caused by nerve or muscle problems.

Recap of GI Anatomy and Function

The Alimentary Canal extends from the mouth to the anus, and includes accessory organs like liver and pancreas.
There are six stages in the process of dealing with food: ingestion, mechanical breakdown, propulsion, digestion, absorption, and defecation.
All sections of the alimentary canal have 4 layers (mucosa, submucosa, muscularis externa, and serosa).
The digestive system is controlled by nerves. Short nerves in the digestive system (submucosal and myenteric plexus) and long nerves from the brain (parasympathetic).

Recap of Saliva and Swallowing

Saliva, secreted by intrinsic and extrinsic glands, has amylase, mucin, water, and protective elements (defensin, IgA, lysozyme).
Swallowing has a buccal phase, pharyngo-oesophageal phase (blocking off the nasopharynx and trachea), and peristalsis and sphnicter opening.
Different types of cells in the stomach include mucus cells, parietal cells, chief cells, and enteroendocrine cells.

Regulation of Gastric Secretion

The regulation of gastric secretion involves the cephalic phase, gastric phase, and intestinal phase.
1. The cephalic phase is initiated in the brain in response to the thought, smell, or sight of food.
1. The gastric phase is initiated by the presence of food in the stomach.
1. The intestinal phase is initiated when chyme enters the small intestine. These phases work together to control stomach acid production.

Gastric Glands and Juices

Gastric glands secrete gastric juices, the most noteworthy being mucus neck cells, parietal cells, and chief cells.
Mucus neck cells are located in the duct portion and secrete mucus.
Parietal cells are in the middle of glands; they secrete hydrochloric acid (HCl) and intrinsic factor.
Chief cells are the bottom of the glands and secrete pepsinogen.

Digestive Processes of the Stomach

The stomach acts as a holding vessel for ingested food and aids in mechanical and chemical digestion.
Protein digestion takes place with HCl denaturing proteins, activating pepsinogen to pepsin, pepsin breaking peptide bonds of proteins, and rennin breaking down casein (a protein in milk).
Mucous barriers protect the stomach lining from its secretions, whereas intrinsic factor aids in vitamin B12 absorption.
The stomach lining is replaced every 3 to 6 days.

Dyspepsia

Dyspepsia is a group of upper gastrointestinal symptoms, not a diagnosis itself. Symptoms include upper abdominal pain, heartburn, gastric reflux, nausea, or vomiting.
The causes of dyspepsia range from gastric and duodenal ulcers to gastro-oesophageal reflux disease (GORD), oesophagitis, etc to esophageal or gastric cancers.

Pharmacological Treatments

Mucosal strengtheners such as Misoprostol.
Reduction of acid secretion through proton pump inhibitors, e.g., omeprazole; histamine H2 receptor antagonists, e.g., ranitidine; and muscarinic antagonists, e.g., pirenzepine.
Eradication of H pylori via dual therapy (PPI and antibiotics).

Gastroparesis

Gastroparesis is delayed gastric emptying in the absence of mechanical obstruction.
Associated conditions are diabetes mellitus, hypothyroidism, neurological conditions, viral infections, and autoimmune attacks.
This can happen due to latrogenic causes including vagal nerve damage during surgery, opioid use, alpha-2-adrenergic agonist use (e.g., clonidine), tricyclic antidepressants, and anticholinergics.

Promotility Agents

Agents used to promote the passage of ingested material in the GI tract may include:
Gastroparesis and constipation.
Neurogastroenterology and motility.
Enteric neuro-modulation.
Consideration for valid simple gut motility stimulation, as well as potentially poorly defined target disorders. Non-selective drugs often come with side effects.

How Do Promotility Agents Work?

Promotility agents can increase wave-like contractions in the esophagus, stomach, and intestines. Methods involved include stimulating excitatory chemical messengers like acetylcholine and suppressing inhibitory neurotransmitters like dopamine and serotonin.

Dopamine Antagonists

Metoclopramide and domperidone are first-line therapies for hypomotility disorders.
These drugs block dopamine's effects in the central nervous system and the chemoreceptor trigger zone to improve peristalsis and may lessen nausea.
Metoclopramide can cause side effects in about 25% of patients.
Domperidone is generally preferred due to fewer central nervous system effects.

Serotonergic Agonists

Cisapride and Prucalopride are serotonergic antagonists and may help to accelerate intestinal transit, reduce esophageal acid exposure, and improve gastric emptying.

Motilides

Erythromycin is a macrolide antibiotic that can be used to treat gastric stasis and may enhance peristalsis.

Description of Constipation

Infrequent or difficult stool passage or seeming incomplete defecation is a sign of constipation.
It occurs at any age but is common in women, especially during pregnancy, and in the elderly.
New-onset constipation, especially in patients over 50 years old, with accompanying symptoms such as anemia, abdominal pain, weight loss, or blood in the stool, may indicate malignancy.
Certain medications can also cause secondary constipation.

Colon

The colon's role is to convert chyme into feces and excrete it.
The large intestine lacks villi and has many Lieberkühn crypts, which contain mucus-secreting goblet cells.
The colonic mucosa absorbs substances, such as water, sodium, and chloride, through active transport.
Longitudinal bands called the tenia coli help to structure the colon.

Secretion in the Colon

Mucus in the colon neutralizes stomach acid, protects against irritation, lubricates feces, and binds them together.
Defecation reflexes stimulate pelvic nerves, causing increased peristaltic motility, which leads to a marked increase in mucus secretion.
Bacterial infections can cause the colon to secrete water and electrolytes, leading to rapid bowel movements.

Absorption in the Large Intestines

About 0.5 to 1.5 liters of water are absorbed daily in the large intestines.
Key elements include absorption of water, sodium, chloride, and several different vitamins, depending on the specific vitamin.
Certain drugs, such as steroids and aspirin, are absorbed, whereas Vitamin B12 is not absorbed.

Control of Motility in the Colon

Haustrations (mixing movement) occur in the proximal colon with contractions in the circular and longitudinal muscles that form pockets or haustra.
Simultaneous contraction and relaxation of these pockets move material forward.
Mass propagated contractions occur in the distal portion of the colon, occurring roughly 15 minutes after breakfast, and moving stool forward.

Defecation

Defecation is regulated by the stretch of the rectal wall, which sends signals to the spinal cord (SC).
Efferent pelvic impulses cause reflex contractions of the rectum while relaxing the internal anal sphincter.
Tonic contractions of the external anal sphincter can be overridden to allow voluntary control of defecation.
The process is assisted by pelvic floor muscles that contract to expel feces.

Constipation

Constipation is characterized by infrequent bowel movements with small, hard stools or fecal impaction.
Possible causes include poor diet (lack of fiber), decreased gastrointestinal motility, GI tract disorders (like IBS), medications (e.g., opioids), and physical blockages (like colonic carcinoma).

Note on Saline Laxatives

Magnesium citrate and sodium phosphate are used rectally to cleanse the bowels in preparation for procedures.
Laxatives containing magnesium should be avoided in children, individuals with renal impairment, and those with cardiac conditions or pre-existing electrolyte imbalances due to increased risk of hypermagnesemia (associated potentially with heart block/neuromuscular block/CNS depression) and hyperphosphatemia.

Diarrhea

Inflammatory diarrhea involves inflammation of the gastrointestinal tract epithelium, possibly caused by invasive pathogens or inflammatory bowel disease.
Non-inflammatory diarrhea types may be secretory (increased water and electrolyte secretion due to factors like lactose) or osmotic (undigested nutrients pulling water into the gut).

Treatment of Diarrhea

Treating dehydration is crucial, use oral rehydration solutions.
Diet adjustments, avoiding dairy, and antibiotics are common treatment methods.
Antimotility drugs like loperamide may be used when appropriate. Certain considerations such as geographic predisposition to disease and patient's immune status, as well as stool testing and/or blood work should be considered.

Vomiting

The vomiting reflex involves the following steps: initial stimulation, vomiting center activation, retching, and expulsion.
Different parts of the nervous system control the reflex through cranial nerves and the chemoreceptor trigger zone/central vomiting center activation.
The process involves relaxation of esophageal sphincters, contraction of abdominal muscles, and forceful expelled contents.

Anti-emetics

Anti-emetics are used to treat nausea and vomiting, they work by blocking specific receptors.
Drugs in this category include: histamine 1 receptor antagonists, 5-HT3 receptor antagonists, dopamine 2 receptor antagonists, and muscarinic receptor antagonists. These drugs directly block or counteract the neurotransmitters/chemicals that elicit nausea/vomiting symptoms.

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Description

Test your knowledge on gastrointestinal pharmacology with this quiz. Questions cover topics such as colonic function, secretion mechanisms, and drug actions related to digestive health. Perfect for students and professionals in the medical field.