Gastrointestinal Motility — MCQs
On esophageal manometry, spastic contractions in the esophageal body with a distal contractile integral (DCI) >8000 mmHg*s*cm are diagnostic of:
Second swallowing in barium meal studies is found in-
Which cells are referred to as "Pacemaker cells" with relation to "BER"?
Motility in the upper third of the esophagus is decreased in all of the following conditions except which one?
All the following mediate their action using cAMP as second messenger except:
In which of the following conditions is uniform dilation of the esophagus seen?
What is the primary function of the myenteric plexus?
Slow wave potentials originate in which cells of the intestine?
What is the effect of cholecystokinin on the gastrointestinal tract?
Inhibition of myenteric plexus results in
Gastrointestinal Motility Indian Medical PG Practice Questions and MCQs
Question 1: On esophageal manometry, spastic contractions in the esophageal body with a distal contractile integral (DCI) >8000 mmHg*s*cm are diagnostic of:
- A. Jackhammer esophagus
- B. Type II achalasia
- C. Type III achalasia (Correct Answer)
- D. Type I achalasia
Explanation: ***Type III achalasia*** - This diagnosis is characterized by the presence of **spastic contractions** in the esophageal body, specifically with a **distal contractile integral (DCI) greater than 8000 mmHg*s*cm**, alongside the classic features of achalasia (impaired LES relaxation and absent peristalsis) [1]. - The elevated DCI reflects the **premature and simultaneous contractions** that are hallmark of this subtype, distinguishing it from other motility disorders [1]. *Jackhammer esophagus* - While it also involves very strong esophageal contractions (**high DCI**), jackhammer esophagus (also known as hypercontractile esophagus) does **not present with impaired LES relaxation or absent peristalsis** as seen in achalasia. - The defining feature of jackhammer esophagus is **multiple rapid swallows** (MRS) that induce simultaneous contractions, often with very high vigor. *Type II achalasia* - This type of achalasia is defined by **pan-esophageal pressurization** in more than 20% of swallows, along with impaired LES relaxation and absent peristalsis. - Unlike Type III, it does **not show the spastic hypercontractile activity** in the esophageal body revealed by a very high DCI. *Type I achalasia* - This is the classic form of achalasia characterized by **absent esophageal peristalsis** and **impaired lower esophageal sphincter (LES) relaxation**, without significant esophageal pressurization or spastic contractions [1]. - It represents the most common subtype and lacks the **high DCI spastic activity** seen in Type III achalasia.
Question 2: Second swallowing in barium meal studies is found in-
- A. Scleroderma
- B. Reflux esophagitis
- C. Pharyngeal pouch (Correct Answer)
- D. Achalasia cardia
Explanation: ***Pharyngeal pouch*** - A pharyngeal pouch, specifically a **Zenker's diverticulum**, can lead to food or barium pooling within the pouch. - This pooling can cause a sensation of retained material, prompting a **second swallow** to clear the pharynx and esophagus. *Scleroderma* - Leads to **esophageal dysmotility** due to smooth muscle atrophy and fibrosis, primarily affecting the lower two-thirds of the esophagus. - This manifests as difficulty moving food down the esophagus, but not typically as the need for a second swallow to clear a pouch. *Reflux esophagitis* - Characterized by **inflammation of the esophagus** due to gastric acid reflux. - Symptoms include heartburn and dysphagia, but it does not cause the pooling of barium requiring a second swallow as seen with a pharyngeal pouch. *Achalasia cardia* - Involves the **failure of the lower esophageal sphincter to relax** and loss of peristalsis in the esophageal body. - This results in significant delayed emptying and a "bird's beak" appearance on barium swallow, but not the specific finding of a second swallow to clear a localized pouch.
Question 3: Which cells are referred to as "Pacemaker cells" with relation to "BER"?
- A. SA node
- B. AV node
- C. Interstitial cells of Cajal (Correct Answer)
- D. Pyramidal cells
Explanation: ***Interstitial cells of Cajal*** - The **Interstitial cells of Cajal (ICC)** are specialized cells in the gastrointestinal tract that act as the **pacemaker cells** for the **Basic Electrical Rhythm (BER)**. - They generate slow waves of **depolarization** and **repolarization**, which determine the frequency and rhythm of smooth muscle contractions. *SA node* - The **sinoatrial (SA) node** is the natural pacemaker of the **heart**, initiating the cardiac electrical impulse. - It controls the heart rate, not the **BER** of the gastrointestinal tract. *AV node* - The **atrioventricular (AV) node** is part of the heart's electrical conduction system, responsible for delaying and transmitting impulses from the atria to the ventricles. - It does not regulate the **BER** of the gastrointestinal system. *Pyramidal cells* - **Pyramidal cells** are a type of neuron found in various parts of the brain, particularly the cerebral cortex and hippocampus. - They are involved in cognitive functions and motor control, and have no role in generating the **BER** in the gut.
Question 4: Motility in the upper third of the esophagus is decreased in all of the following conditions except which one?
- A. Pseudo-bulbar palsy
- B. Chagas disease
- C. Myasthenia gravis
- D. Scleroderma (Correct Answer)
Explanation: ***Scleroderma*** - **Scleroderma** primarily affects the **smooth muscle** of the distal two-thirds of the esophagus, leading to decreased motility and reflux [1]. - The **upper third of the esophagus** consists of **striated muscle** and is typically spared in scleroderma [1]. *Pseudo-bulbar palsy* - **Pseudo-bulbar palsy** involves motor neuron damage affecting the **corticobulbar tracts**, leading to impaired function of the **striated muscles** of the pharynx and upper esophagus. - This results in **dysphagia** and reduced motility in the voluntary phase of swallowing, which includes the upper third of the esophagus. *Chagas disease* - **Chagas disease** causes destruction of **ganglion cells** in the myenteric plexus, leading to denervation of the smooth muscle. - While it primarily affects the **distal esophagus** (leading to megaesophagus), it can also impact the coordinated activity of the **gastrointestinal tract**, including the more complex coordination required for the upper esophagus, especially if there's extensive involvement. *Myasthenia gravis* - **Myasthenia gravis** is an **autoimmune disorder** characterized by antibodies against **acetylcholine receptors** at the neuromuscular junction, affecting **striated muscles** [1], [2]. - Since the **upper third of the esophagus** is composed of striated muscle, its function is often impaired in myasthenia gravis, leading to **dysphagia** [1].
Question 5: All the following mediate their action using cAMP as second messenger except:
- A. Glucagon
- B. Dopamine
- C. Corticotropin
- D. Vasopressin (Correct Answer)
Explanation: ***Vasopressin (ADH)*** - Vasopressin has **dual signaling mechanisms** depending on receptor type: - **V2 receptors** (kidney collecting duct): Use **Gs-protein → cAMP pathway** for water reabsorption via aquaporin-2 insertion - **V1 receptors** (vascular smooth muscle): Use **Gq-protein → IP3/DAG pathway** for vasoconstriction - In the context of this question, vasopressin is considered the exception because it has **significant non-cAMP mediated actions** through V1 receptors, unlike the other hormones listed which **predominantly or exclusively** use cAMP - **Note**: This is a teaching point about receptor subtypes; vasopressin DOES use cAMP at V2 receptors *Glucagon* - **Exclusively uses cAMP pathway** in hepatocytes and adipocytes - Binds to **glucagon receptor** (GPCR) → **Gs-protein** → adenylyl cyclase activation → **increased cAMP** → PKA activation - Promotes glycogenolysis, gluconeogenesis, and lipolysis *Dopamine* - **D1 and D5 receptors** are **Gs-coupled** → **stimulate adenylyl cyclase** → **increase cAMP** - Important for neurotransmission (motor control, reward) and renal vasodilation - D2-family receptors (D2, D3, D4) inhibit cAMP but D1-family predominates in many physiological contexts *Corticotropin (ACTH)* - Binds to **melanocortin-2 receptor (MC2R)** on adrenal cortex - **Gs-protein coupled** → adenylyl cyclase activation → **increased cAMP** → PKA activation - Stimulates steroidogenesis and cortisol secretion - **Exclusively cAMP-dependent mechanism**
Question 6: In which of the following conditions is uniform dilation of the esophagus seen?
- A. Achalasia and Diffuse esophageal spasm (Correct Answer)
- B. Esophageal strictures and Nutcracker esophagus
- C. Nutcracker esophagus and Esophageal cancer
- D. Esophageal strictures and Esophageal cancer
Explanation: ***Achalasia and Diffuse esophageal spasm*** - In **achalasia**, there is a **loss of ganglion cells** in Auerbach's plexus [1], leading to **impaired relaxation of the lower esophageal sphincter** and a lack of peristalsis in the esophageal body, resulting in proximal dilation [1]. - **Diffuse esophageal spasm** involves **simultaneous, high-amplitude, non-peristaltic contractions** causing dysphagia and chest pain, which can lead to a "corkscrew" appearance on imaging but also generalized esophageal dilation due to inefficient bolus transit. *Esophageal strictures and Nutcracker esophagus* - **Esophageal strictures** typically cause **focal narrowing** of the esophagus, proximal to which there may be dilation [2], but not uniform dilation along the entire length. - **Nutcracker esophagus** is characterized by **high-amplitude peristaltic contractions** and does not typically involve uniform esophageal dilation [2]. *Nutcracker esophagus and Esophageal cancer* - As mentioned, **Nutcracker esophagus** features strong, coordinated contractions but **no structural dilation** [2]. - **Esophageal cancer** often presents as a **focal mass** or stricture, which can obstruct the lumen and cause proximal dilation, but not uniform dilation. *Esophageal strictures and Esophageal cancer* - Both **esophageal strictures** and **esophageal cancer** are typically associated with **localized narrowing** and obstruction, leading to focal or proximal dilation rather than a uniform dilation of the entire esophagus.
Question 7: What is the primary function of the myenteric plexus?
- A. Regulating GI secretion
- B. Regulating local blood flow
- C. Regulating motility (Correct Answer)
- D. Regulating absorption
Explanation: ***Regulating motility*** - The myenteric plexus, also known as **Auerbach's plexus**, is primarily responsible for coordinating the **rhythmic contractions** and **relaxation of the gastrointestinal (GI) smooth muscle**. - Its strategic location between the **longitudinal and circular muscle layers** allows it to directly influence the strength and frequency of peristalsis, thus regulating the movement of food through the digestive tract. *Regulating GI secretion* - While it has some indirect influence, the **submucosal plexus** (Meissner's plexus) is the primary neural network regulating **secretory functions** of the GI tract. - The myenteric plexus's main role is more directly related to muscle contraction and relaxation rather than glandular secretion. *Regulating local blood flow* - Local blood flow in the GI tract is primarily regulated by the **sympathetic and parasympathetic nervous systems**, along with local metabolic factors and hormones. - The myenteric plexus has a minimal direct role in the control of **GI blood vessel smooth muscle**. *Regulating absorption* - Absorption is primarily a function of the **intestinal epithelial cells** and is regulated by various transport mechanisms, hormones, and local factors. - While the enteric nervous system influences mucosal function indirectly, the myenteric plexus's primary role is **motor control** rather than directly regulating nutrient absorption processes.
Question 8: Slow wave potentials originate in which cells of the intestine?
- A. Myenteric plexus
- B. Parasympathetic neurons
- C. Smooth muscle cells
- D. Interstitial cells of Cajal (Correct Answer)
Explanation: ***Interstitial cells of Cajal*** - The **interstitial cells of Cajal (ICC)** are specialized mesenchymal cells that act as **pacemaker cells** for the gastrointestinal tract. - They generate **slow wave potentials** (basic electrical rhythm), which are oscillating depolarizations and repolarizations of the smooth muscle cell membrane potential. *Myenteric plexus* - The **myenteric plexus (Auerbach's plexus)** primarily controls **gastrointestinal motility** through neural pathways. - It modulates the frequency and strength of contractions but does not directly generate the slow wave potentials. *Parasympathetic neurons* - **Parasympathetic neurons** release neurotransmitters (e.g., acetylcholine) that **modulate the activity** of smooth muscle and ICC, enhancing or inhibiting slow wave activity. - They do not, however, originate the slow wave potential itself. *Smooth muscle cells* - **Smooth muscle cells** are the effector cells that contract in response to the slow waves and action potentials. - While they undergo the depolarization and repolarization of slow waves, the **initiating pacemaker activity** comes from the ICC.
Question 9: What is the effect of cholecystokinin on the gastrointestinal tract?
- A. Increases gastric acid secretion
- B. Increases gastric motility
- C. Relaxes gall bladder
- D. Increases small intestinal peristalsis (Correct Answer)
Explanation: ***Increases small intestinal peristalsis*** - **Cholecystokinin (CCK)** is released in response to fat and protein in the duodenum and plays a significant role in **digestion and absorption**. - One of its key functions is to enhance **small intestinal motility**, facilitating the mixing and propulsion of chyme for efficient digestion and nutrient absorption. *Increases gastric acid secretion* - **Gastrin** is the primary hormone responsible for increasing **gastric acid secretion**, stimulated by protein and amino acids in the stomach. - While CCK shares structural similarities with gastrin, its predominant effect on gastric acid is typically inhibitory, especially at physiological concentrations, to allow for intestinal processing. *Increases gastric motility* - CCK generally has an **inhibitory effect on gastric emptying and motility**, helping to slow down the rate at which food leaves the stomach. - This allows adequate time for the small intestine to process the incoming chyme, particularly rich in fats, by coordinating with **pancreatic enzyme** and **bile release**. *Relaxes gall bladder* - CCK is known for its potent ability to **contract the gallbladder**, leading to the expulsion of bile into the duodenum. - This action is crucial for **emulsifying dietary fats** and aiding in their digestion and absorption.
Question 10: Inhibition of myenteric plexus results in
- A. Hyperacidity
- B. Diarrhea
- C. Decreased gut motility (Correct Answer)
- D. Increased secretions
Explanation: ***Decreased gut motility*** - The **myenteric plexus** (Auerbach's plexus) is primarily responsible for regulating **gastrointestinal motility**, including peristalsis and muscle contraction. - Its inhibition would therefore lead to **reduced peristaltic movements** and **decreased gut motility**. *Hyperacidity* - **Gastric acid secretion** is mainly regulated by the vagus nerve (via acetylcholine), gastrin, and histamine, not directly by the myenteric plexus. - While gut motility can indirectly affect acid exposure, a primary and direct consequence of myenteric plexus inhibition is not hyperacidity. *Diarrhea* - **Diarrhea** is typically caused by increased gut motility, increased secretion, or decreased absorption. - Inhibition of the myenteric plexus would lead to **decreased motility**, making diarrhea an unlikely outcome. *Increased secretions* - **Gastrointestinal secretions** are largely controlled by the submucosal plexus (Meissner's plexus) and hormonal factors. - While the myenteric plexus has some indirect influence, its primary role is motility, and its inhibition would not directly lead to increased secretions.
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