Topic: Gastrointestinal Physiology
Subtopic: Gastric Hormones
Keyword Definitions:
- Delta cells: Specialized cells in the stomach and pancreas that secrete somatostatin.
- Cholecystokinin: Hormone stimulating gallbladder contraction and pancreatic enzyme secretion.
- Gastrin-releasing peptide: Neurotransmitter that stimulates gastrin secretion.
- Somatostatin: Hormone that inhibits secretion of various other hormones, including gastrin, insulin, and glucagon.
- Secretin: Hormone that stimulates bicarbonate secretion from the pancreas.
Lead Question - 2013
"Delta cells" of stomach secrete ?
a) Cholecystokinin
b) Gastrin-releasing peptide
c) Somatostatin
d) Secretin
Answer and Explanation:
Correct answer is c) Somatostatin. Delta cells, located in the gastric mucosa, secrete somatostatin which inhibits the secretion of other hormones like gastrin and insulin. This helps regulate acid production in the stomach and maintain homeostasis by reducing excessive hormone release, ensuring proper digestive function.
Guessed Questions for NEET PG:
1. Gastrin primarily stimulates?
a) Acid secretion
b) Bile secretion
c) Pancreatic enzyme secretion
d) Insulin release
Explanation: Correct answer is a) Acid secretion. Gastrin stimulates parietal cells to secrete hydrochloric acid, aiding digestion and maintaining stomach pH.
2. Somatostatin inhibits secretion of?
a) Gastrin
b) Insulin
c) Glucagon
d) All of the above
Explanation: Correct answer is d) All of the above. Somatostatin broadly inhibits gastrin, insulin, and glucagon, regulating digestive and metabolic processes.
3. Secretin release is triggered by?
a) Acidic chyme in duodenum
b) Fatty food in stomach
c) Glucose in blood
d) Low plasma calcium
Explanation: Correct answer is a) Acidic chyme in duodenum. Secretin stimulates pancreatic bicarbonate secretion to neutralize acidic chyme.
4. Cholecystokinin (CCK) stimulates?
a) Gallbladder contraction
b) Pancreatic bicarbonate release
c) Gastric acid secretion
d) Water absorption
Explanation: Correct answer is a) Gallbladder contraction. CCK promotes gallbladder contraction and enzyme secretion from the pancreas.
5. G cells secrete?
a) Secretin
b) Gastrin
c) Somatostatin
d) Pepsin
Explanation: Correct answer is b) Gastrin. G cells in the antrum of the stomach secrete gastrin to stimulate acid secretion.
6. Somatostatin acts by inhibiting which cell type?
a) Parietal cells
b) Chief cells
c) Enterochromaffin cells
d) All of the above
Explanation: Correct answer is d) All of the above. Somatostatin inhibits multiple cell types to suppress acid and enzyme secretion.
7. Effect of somatostatin on motility?
a) Increases
b) Decreases
c) No effect
d) Variable
Explanation: Correct answer is b) Decreases. Somatostatin reduces gastrointestinal motility, slowing digestion.
8. Major site of somatostatin secretion?
a) Stomach
b) Pancreas
c) Hypothalamus
d) All of the above
Explanation: Correct answer is d) All of the above. Somatostatin is secreted from multiple sites, regulating hormone secretion and digestion.
9. Primary effect of secretin?
a) Increases gastric acid
b) Stimulates bile production
c) Stimulates pancreatic bicarbonate secretion
d) Inhibits gastrin
Explanation: Correct answer is c) Stimulates pancreatic bicarbonate secretion. Secretin neutralizes acidic chyme entering the duodenum.
10. Gastrin secretion is stimulated by?
a) Vagal stimulation
b) Low pH
c) High glucose
d) High fatty acids
Explanation: Correct answer is a) Vagal stimulation. Vagal activation promotes gastrin release during digestion.
Topic: Gastrointestinal Physiology
Subtopic: Absorption of Nutrients
Keyword Definitions:
- Duodenum: First part of the small intestine immediately beyond the stomach, where most chemical digestion occurs.
- Jejunum: Middle section of the small intestine where the majority of nutrient absorption occurs.
- Ileum: Last part of the small intestine responsible for absorbing vitamin B12 and bile salts.
- Ascending colon: First part of the large intestine involved in water absorption and formation of feces.
- Sugars absorption: Process by which monosaccharides are transported from the intestine into the blood.
Lead Question - 2013
Sugars are primarily absorbed in ?
a) Duodenum
b) Jejunum
c) Ileus
d) Ascending colon
Answer and Explanation:
Correct answer is b) Jejunum. The jejunum is the main site of sugar absorption due to its extensive surface area and abundance of transporters like SGLT1 and GLUT2, which facilitate the uptake of monosaccharides into the bloodstream, ensuring efficient nutrient absorption for energy production.
Guessed Questions for NEET PG:
1. Glucose absorption mechanism in intestine is via?
a) Passive diffusion
b) Active transport
c) Osmosis
d) Pinocytosis
Explanation: Correct answer is b) Active transport. Glucose absorption occurs by active transport using SGLT1 and facilitated diffusion via GLUT transporters in the small intestine.
2. Lactose is hydrolyzed by?
a) Maltase
b) Sucrase
c) Lactase
d) Amylase
Explanation: Correct answer is c) Lactase. Lactase enzyme breaks lactose into glucose and galactose for absorption in the small intestine.
3. Primary site for fat absorption?
a) Duodenum
b) Jejunum
c) Ileum
d) Colon
Explanation: Correct answer is b) Jejunum. The jejunum efficiently absorbs lipids after emulsification and micelle formation in the small intestine.
4. Which transporter is important for glucose uptake?
a) SGLT1
b) SGLT2
c) GLUT4
d) Na+/K+ ATPase
Explanation: Correct answer is a) SGLT1. SGLT1 actively transports glucose into enterocytes across the apical membrane in the small intestine.
5. Monosaccharides absorbed into blood via?
a) Facilitated diffusion
b) Simple diffusion
c) Active transport
d) Endocytosis
Explanation: Correct answer is a) Facilitated diffusion. GLUT2 transporter moves monosaccharides into circulation by facilitated diffusion.
6. Absorption of fructose is by?
a) Active transport
b) Facilitated diffusion
c) Endocytosis
d) Simple diffusion
Explanation: Correct answer is b) Facilitated diffusion. Fructose enters enterocytes through GLUT5 and exits via GLUT2.
7. Site of vitamin B12 absorption?
a) Duodenum
b) Jejunum
c) Ileum
d) Colon
Explanation: Correct answer is c) Ileum. Vitamin B12 absorption requires intrinsic factor and occurs in the ileum.
8. Na+-Glucose co-transport occurs at?
a) Apical membrane
b) Basolateral membrane
c) Nuclear membrane
d) Mitochondrial membrane
Explanation: Correct answer is a) Apical membrane. SGLT1 co-transports sodium and glucose into enterocytes across the apical membrane.
9. Lactose intolerance due to deficiency of?
a) Sucrase
b) Maltase
c) Lactase
d) Amylase
Explanation: Correct answer is c) Lactase. Lactase deficiency causes lactose intolerance, leading to malabsorption and gastrointestinal symptoms.
10. Glucose in enterocyte exits to blood by?
a) SGLT1
b) GLUT2
c) GLUT4
d) Na+/K+ ATPase
Explanation: Correct answer is b) GLUT2. GLUT2 transports glucose from enterocyte into the bloodstream by facilitated diffusion.
Topic: Digestive Enzymes
Subtopic: Activation of Pancreatic Enzymes
Keyword Definitions:
- Trypsinogen: Inactive precursor (zymogen) of trypsin, secreted by the pancreas.
- Trypsin: Active proteolytic enzyme that digests proteins in the small intestine.
- Phosphorylation: Addition of a phosphate group to a molecule, often to regulate enzyme activity.
- Amino acids: Building blocks of proteins; removal of specific amino acids activates some zymogens.
- Alkyl group: Hydrocarbon group added in chemical modifications, not involved in trypsinogen activation.
Lead Question - 2013
Trypsinogen is converted to trypsin by?
a) Combination of 2 molecules of trypsinogen
b) Phosphorylation
c) Removal of few amino acids from trypsinogen
d) Addition of alkyl group
Answer and Explanation:
Correct answer is c) Removal of few amino acids from trypsinogen. Trypsinogen is activated in the duodenum when the enzyme enteropeptidase removes a specific peptide segment, converting it into active trypsin. This activation is crucial for digestion of proteins, preventing premature enzyme activity in the pancreas.
Guessed Questions for NEET PG:
1. Enteropeptidase is secreted by?
a) Pancreas
b) Liver
c) Duodenal mucosa
d) Stomach
Explanation: Correct answer is c) Duodenal mucosa. Enteropeptidase is secreted by duodenal epithelial cells and activates trypsinogen to trypsin, initiating protein digestion.
2. Trypsin activates?
a) Pepsinogen
b) Other pancreatic zymogens
c) Amylase
d) Lipase
Explanation: Correct answer is b) Other pancreatic zymogens. Trypsin activates chymotrypsinogen, proelastase, and procarboxypeptidase into their active forms for protein digestion.
3. Trypsin inhibitor prevents?
a) Activation of pepsin
b) Auto-digestion of pancreas
c) Amylase secretion
d) Fat absorption
Explanation: Correct answer is b) Auto-digestion of pancreas. Trypsin inhibitor prevents premature activation of trypsinogen within the pancreas, protecting pancreatic tissue.
4. Zymogens are?
a) Active enzymes
b) Inactive enzyme precursors
c) Hormones
d) Transport proteins
Explanation: Correct answer is b) Inactive enzyme precursors. Zymogens like trypsinogen are activated by specific cleavage for controlled enzyme function.
5. Trypsin is a type of?
a) Lipase
b) Protease
c) Amylase
d) Nuclease
Explanation: Correct answer is b) Protease. Trypsin breaks down proteins into peptides in the small intestine.
6. Clinical relevance of trypsinogen activation defect?
a) Cystic fibrosis
b) Pancreatitis
c) Diabetes
d) Hyperthyroidism
Explanation: Correct answer is b) Pancreatitis. Premature activation of trypsinogen in the pancreas leads to autodigestion and pancreatitis.
7. Trypsin cleaves peptide bonds at?
a) Aromatic amino acids
b) Basic amino acids
c) Acidic amino acids
d) Non-polar amino acids
Explanation: Correct answer is b) Basic amino acids. Trypsin specifically cleaves peptide bonds after lysine and arginine residues.
8. Trypsinogen is secreted by?
a) Stomach
b) Liver
c) Pancreas
d) Gallbladder
Explanation: Correct answer is c) Pancreas. The pancreas secretes trypsinogen into the duodenum for protein digestion.
9. Inactive form of enzymes are called?
a) Hormones
b) Zymogens
c) Coenzymes
d) Substrates
Explanation: Correct answer is b) Zymogens. Trypsinogen is a zymogen, activated only in the intestine to prevent tissue damage.
10. Trypsinogen activation site?
a) Stomach
b) Duodenum
c) Jejunum
d) Ileum
Explanation: Correct answer is b) Duodenum. Enteropeptidase in the duodenum converts trypsinogen into active trypsin, triggering digestive enzyme cascade.
Topic: Gastrointestinal Physiology
Subtopic: Fermentation of Plant Components
Keyword Definitions:
- Lignin: A complex polymer in plant cell walls providing rigidity, resistant to microbial fermentation.
- Cellulose: A polysaccharide of glucose units; fermented by gut bacteria into short-chain fatty acids.
- Hemicellulose: Heteropolysaccharide in plant cell walls; partially fermented by gut microbes.
- Pectin: Soluble fiber in plant cell walls, readily fermented by gastrointestinal microorganisms.
Lead Question - 2013
Which of the following plant components is not fermented by gastrointestinal microorganisms?
a) Lignin
b) Cellulose
c) Hemicellulose
d) Pectin
Answer and Explanation:
Correct answer is a) Lignin. Lignin is a highly complex and rigid polymer in plant cell walls that is resistant to fermentation by gastrointestinal microorganisms. Unlike cellulose, hemicellulose, and pectin, lignin provides structural support and is not broken down by microbial enzymes, passing largely undigested through the GI tract.
Guessed Questions for NEET PG:
1. Cellulose is fermented into?
a) Glucose
b) Short-chain fatty acids
c) Amino acids
d) Proteins
Explanation: Correct answer is b) Short-chain fatty acids. Cellulose is fermented by gut microbes into short-chain fatty acids like acetate, propionate, and butyrate, which serve as energy sources for colonocytes.
2. Pectin fermentation produces?
a) Carbon dioxide
b) Methane
c) Short-chain fatty acids
d) Ethanol
Explanation: Correct answer is c) Short-chain fatty acids. Pectin is readily fermented in the colon, producing SCFAs that contribute to colonic health and provide energy.
3. Lignin passes through GI tract because?
a) Easily soluble
b) Resistant to enzymes
c) Converted into SCFAs
d) Digested by gut flora
Explanation: Correct answer is b) Resistant to enzymes. Lignin's complex structure resists breakdown by digestive enzymes and microbial fermentation, remaining mostly undigested.
4. Hemicellulose differs from cellulose by?
a) Only glucose units
b) Heterogeneous sugars
c) Protein content
d) No fermentation
Explanation: Correct answer is b) Heterogeneous sugars. Hemicellulose consists of various sugars, unlike cellulose's glucose-only chain, allowing partial microbial fermentation.
5. Which fiber is most fermentable?
a) Lignin
b) Cellulose
c) Pectin
d) Hemicellulose
Explanation: Correct answer is c) Pectin. Pectin is highly fermentable, producing beneficial SCFAs for colon health.
6. Microbial fermentation occurs in?
a) Stomach
b) Small intestine
c) Large intestine
d) Esophagus
Explanation: Correct answer is c) Large intestine. The colon hosts abundant microbes that ferment dietary fibers into SCFAs and gases.
7. Insoluble fiber example is?
a) Pectin
b) Lignin
c) Inulin
d) Oligosaccharides
Explanation: Correct answer is b) Lignin. Lignin is an insoluble fiber that adds bulk and passes undigested, unlike soluble fibers that are fermentable.
8. Major benefit of fiber fermentation?
a) Protein synthesis
b) SCFA production
c) Vitamin B12 absorption
d) Increased lipid absorption
Explanation: Correct answer is b) SCFA production. Microbial fermentation of fiber yields short-chain fatty acids, important for colon health and systemic metabolism.
9. Non-fermentable dietary fiber helps in?
a) SCFA production
b) Stool bulking
c) Sugar absorption
d) Fat digestion
Explanation: Correct answer is b) Stool bulking. Non-fermentable fibers like lignin add bulk to stool and promote bowel regularity.
10. Excess fermentation can cause?
a) Constipation
b) Diarrhea
c) Gas and bloating
d) Hyperglycemia
Explanation: Correct answer is c) Gas and bloating. Excessive microbial fermentation of fibers may produce gases causing bloating and discomfort.
Topic: Digestive System
Subtopic: Bile Salts and Their Functions
Keyword Definitions:
- Bile salts: Molecules derived from cholesterol that aid in fat digestion by emulsifying lipids.
- Hydropathic: Relates to interactions involving water affinity or repulsion.
- Zwitter ion: A molecule containing both positive and negative charges but overall neutral.
- Amphipathic: Molecules having both hydrophilic (water-attracting) and hydrophobic (water-repelling) regions.
Lead Question - 2013
Detergent action of bile salts is due to:
a) Hydropathic
b) Acts as a zwitter ion
c) Amphipathic
d) All
Answer and Explanation:
Correct answer is c) Amphipathic. The detergent action of bile salts is primarily due to their amphipathic nature, allowing them to emulsify lipids by interacting with both water and lipid molecules. This enhances fat digestion by increasing the surface area accessible to pancreatic lipase.
Guessed Questions for NEET PG:
1. Bile salts are synthesized in?
a) Pancreas
b) Liver
c) Stomach
d) Small intestine
Explanation: Correct answer is b) Liver. Bile salts are synthesized in the liver from cholesterol and secreted into bile to aid in digestion.
2. Major component of bile salts is derived from?
a) Proteins
b) Cholesterol
c) Carbohydrates
d) Nucleic acids
Explanation: Correct answer is b) Cholesterol. Bile salts are synthesized from cholesterol, aiding in emulsification and absorption of dietary fats.
3. Bile salt deficiency leads to?
a) Diarrhea
b) Fat malabsorption
c) Increased protein digestion
d) Hypoglycemia
Explanation: Correct answer is b) Fat malabsorption. Lack of bile salts impairs fat emulsification, causing steatorrhea and deficiencies in fat-soluble vitamins.
4. Amphipathic property of bile salts helps in?
a) Protein digestion
b) Emulsification of fats
c) Carbohydrate breakdown
d) Water absorption
Explanation: Correct answer is b) Emulsification of fats. Amphipathic bile salts stabilize emulsions, increasing surface area for enzymatic action.
5. Zwitter ionic property of bile salts affects?
a) Enzyme activation
b) pH buffering
c) Detergent action
d) Hormone secretion
Explanation: Correct answer is c) Detergent action. Though bile salts can have zwitterionic properties, their detergent action is mainly attributed to amphipathic structure.
6. Hydropathic index relates to?
a) Protein solubility
b) Water-lipid interaction
c) DNA replication
d) Mineral absorption
Explanation: Correct answer is b) Water-lipid interaction. Hydropathic properties influence bile salts’ ability to interact with lipids and aqueous environment.
7. Emulsification increases?
a) Fat droplet size
b) Surface area of lipids
c) Bile acid concentration
d) Cholesterol synthesis
Explanation: Correct answer is b) Surface area of lipids. Emulsification breaks fat into small droplets, increasing surface area for lipase action.
8. Bile salts are reabsorbed in?
a) Stomach
b) Jejunum
c) Ileum
d) Colon
Explanation: Correct answer is c) Ileum. Bile salts are reabsorbed in the terminal ileum and recirculated via the enterohepatic pathway.
9. Conjugation of bile salts occurs with?
a) Glycine
b) Glucose
c) Fructose
d) Galactose
Explanation: Correct answer is a) Glycine. Conjugation with glycine or taurine increases bile salt solubility and effectiveness in emulsification.
10. Excess bile salts in circulation cause?
a) Jaundice
b) Pruritus
c) Anemia
d) Hypotension
Explanation: Correct answer is b) Pruritus. Accumulation of bile salts in blood due to cholestasis leads to intense itching (pruritus).
Topic: Gastrointestinal Secretions
Subtopic: pH of GI Secretions
Keyword Definitions:
- pH: Measure of hydrogen ion concentration, indicating acidity or alkalinity of a solution.
- Gastric juice: Acidic fluid secreted by the stomach, containing hydrochloric acid and digestive enzymes.
- Bile juice: Alkaline fluid produced by the liver, aiding in fat emulsification.
- Saliva: Fluid secreted by salivary glands, aiding in digestion and lubrication of food.
- Pancreatic juice: Alkaline fluid from pancreas containing digestive enzymes for carbohydrates, fats, and proteins.
Lead Question - 2013
Lowest pH is seen in which of the gastrointestinal secretion?
a) Gastric juice
b) Bile juice
c) Saliva
d) Pancreatic juice
Answer and Explanation:
Correct answer is a) Gastric juice. Gastric juice has the lowest pH (approximately 1.5 to 3.5) due to hydrochloric acid secretion by parietal cells, essential for protein digestion and killing pathogens. Other secretions like bile, saliva, and pancreatic juice are neutral to alkaline.
Guessed Questions for NEET PG:
1. Salivary secretion is mainly stimulated by?
a) Parasympathetic stimulation
b) Sympathetic stimulation
c) Hormonal control
d) Voluntary control
Explanation: Correct answer is a) Parasympathetic stimulation. Parasympathetic nerves stimulate copious watery saliva production, aiding digestion and oral hygiene.
2. Bile secretion is stimulated by?
a) Gastrin
b) Secretin
c) CCK (Cholecystokinin)
d) Insulin
Explanation: Correct answer is c) CCK. Cholecystokinin stimulates bile secretion from gallbladder for fat emulsification during digestion.
3. Pancreatic juice pH is approximately?
a) 2
b) 5
c) 7
d) 8
Explanation: Correct answer is d) 8. Pancreatic juice is alkaline (pH ~8), neutralizing acidic chyme and providing optimal pH for enzyme activity.
4. Gastric juice contains which enzyme?
a) Amylase
b) Pepsin
c) Lipase
d) Trypsin
Explanation: Correct answer is b) Pepsin. Pepsinogen converts to pepsin in acidic gastric environment for protein digestion.
5. Bile salts are important for?
a) Protein digestion
b) Fat emulsification
c) Carbohydrate digestion
d) Vitamin B12 absorption
Explanation: Correct answer is b) Fat emulsification. Bile salts break large fat droplets into smaller ones to aid pancreatic lipase action.
6. Major component of saliva aiding starch digestion is?
a) Pepsin
b) Lipase
c) Amylase
d) Protease
Explanation: Correct answer is c) Amylase. Salivary amylase begins starch breakdown into maltose in the oral cavity.
7. Secretin is secreted by?
a) Duodenum
b) Stomach
c) Pancreas
d) Liver
Explanation: Correct answer is a) Duodenum. Secretin released in response to acidic chyme stimulates pancreatic bicarbonate secretion to neutralize acid.
8. Gastric acid secretion is increased by which hormone?
a) Insulin
b) Secretin
c) Gastrin
d) Glucagon
Explanation: Correct answer is c) Gastrin. Gastrin stimulates parietal cells to secrete hydrochloric acid for digestion and pathogen defense.
9. pH of bile is approximately?
a) 1.5
b) 4
c) 7
d) 8
Explanation: Correct answer is d) 8. Bile is alkaline, aiding in neutralizing gastric acid and emulsifying fats for digestion.
10. Which stimulates pancreatic enzyme secretion?
a) Secretin
b) Acetylcholine
c) CCK
d) All of the above
Explanation: Correct answer is d) All of the above. Secretin, CCK, and parasympathetic stimulation promote pancreatic enzyme and bicarbonate secretion.
Topic: Digestive System
Subtopic: Salivary Secretion
Keyword Definitions:
- Salivary Secretion: Production and release of saliva by salivary glands to aid digestion and oral hygiene.
- Saliva: Watery fluid containing enzymes like amylase, mucins, and electrolytes, essential for initial digestion and lubrication of food.
- mL (Milliliter): A unit of volume measurement in the metric system.
Lead Question - 2013
Daily salivary secretion is
a) 250-500 ml
b) 1000-1500 ml
c) 2000-2500 ml
d) 3000 ml
Answer and Explanation:
Correct answer is c) 2000-2500 ml. In a healthy adult, approximately 1.5 to 2.5 liters of saliva are secreted daily. This secretion maintains oral hygiene, initiates starch digestion by amylase, and aids in lubrication and swallowing of food. The quantity may vary with diet and hydration status.
Guessed Questions for NEET PG:
1. Salivary glands include all except?
a) Parotid
b) Submandibular
c) Sublingual
d) Thyroid
Explanation: Correct answer is d) Thyroid. Thyroid is an endocrine gland unrelated to saliva production, whereas parotid, submandibular, and sublingual glands are major salivary glands.
2. Major enzyme in saliva is?
a) Pepsin
b) Amylase
c) Lipase
d) Trypsin
Explanation: Correct answer is b) Amylase. Salivary amylase initiates starch digestion in the oral cavity.
3. Parasympathetic stimulation of salivary glands results in?
a) Viscous secretion
b) Copious watery secretion
c) No secretion
d) Protein secretion
Explanation: Correct answer is b) Copious watery secretion. Parasympathetic activation produces large volumes of watery saliva rich in enzymes.
4. Saliva helps in all except?
a) Starch digestion
b) Lubrication
c) Acid neutralization
d) Blood glucose regulation
Explanation: Correct answer is d) Blood glucose regulation. Saliva aids digestion and lubrication but does not regulate blood glucose levels.
5. Sympathetic stimulation causes?
a) Watery saliva
b) Thick, protein-rich saliva
c) No effect
d) Increased volume
Explanation: Correct answer is b) Thick, protein-rich saliva. Sympathetic input produces small amounts of viscous saliva with higher protein content.
6. Daily salivary secretion is primarily regulated by?
a) Hormones
b) Neural input
c) Blood glucose levels
d) Plasma osmolarity
Explanation: Correct answer is b) Neural input. Both parasympathetic and sympathetic nervous systems regulate saliva production.
7. Saliva pH range is approximately?
a) 4.5-5.5
b) 6.5-7.5
c) 8.0-9.0
d) 5.0-6.0
Explanation: Correct answer is b) 6.5-7.5. Saliva maintains near-neutral pH, buffering acids and maintaining oral health.
8. Saliva composition includes all except?
a) Water
b) Electrolytes
c) Digestive enzymes
d) Red blood cells
Explanation: Correct answer is d) Red blood cells. Saliva is acellular fluid without blood cells; contains water, electrolytes, and enzymes.
9. Sjogren’s syndrome leads to?
a) Increased salivation
b) Decreased salivation
c) Unchanged salivation
d) Excessive enzyme secretion
Explanation: Correct answer is b) Decreased salivation. Autoimmune damage to salivary glands causes dry mouth (xerostomia).
10. Amylase in saliva acts on?
a) Protein
b) Lipids
c) Starch
d) Nucleic acids
Explanation: Correct answer is c) Starch. Salivary amylase catalyzes breakdown of starch into maltose during oral digestion.
Topic: Digestive System
Subtopic: Pancreatic Secretion
Keyword Definitions:
- Pancreatic Juice: Fluid secreted by the pancreas containing digestive enzymes and bicarbonate-rich fluid aiding digestion.
- Electrolytes: Minerals in body fluids responsible for electrical conduction and maintaining osmotic balance.
- Secretin: Hormone released by duodenal S-cells in response to acidic chyme, stimulating pancreatic bicarbonate secretion.
Lead Question - 2013
Pancreatic juice rich in water and electrolytes poor in enzymes is secreted in response to:
a) Pancreozymin
b) Cholecystokinin
c) Secretin
d) Proteins
Answer and Explanation:
Correct answer is c) Secretin. Secretin is released by duodenal S-cells in response to acidic chyme entering the duodenum. It primarily stimulates the pancreas to secrete a bicarbonate-rich, enzyme-poor fluid that helps neutralize gastric acid, providing an optimal environment for enzymatic digestion in the intestine.
Guessed Questions for NEET PG:
1. Cholecystokinin primarily stimulates secretion of:
a) Electrolyte-rich fluid
b) Enzyme-rich pancreatic juice
c) Mucus
d) Bile salts
Explanation: Correct answer is b) Enzyme-rich pancreatic juice. Cholecystokinin (CCK) stimulates acinar cells to release digestive enzymes necessary for protein and fat digestion.
2. Secretin is secreted from which cells?
a) Alpha cells of pancreas
b) S cells of duodenum
c) Chief cells of stomach
d) Goblet cells of intestine
Explanation: Correct answer is b) S cells of duodenum. These cells detect acidic chyme and release secretin to regulate pancreatic secretions and bile flow.
3. Main component of pancreatic juice is:
a) Enzymes
b) Water and bicarbonate
c) Electrolytes only
d) Mucins
Explanation: Correct answer is b) Water and bicarbonate. Pancreatic juice is predominantly aqueous with bicarbonate ions to neutralize acid.
4. Cholecystokinin release is stimulated by presence of:
a) Acidic chyme
b) Fat and protein in duodenum
c) Carbohydrate in stomach
d) Low blood glucose
Explanation: Correct answer is b) Fat and protein in duodenum. CCK secretion increases pancreatic enzyme output for digestion.
5. Secretin regulates pancreatic secretion by:
a) Increasing enzyme release
b) Increasing bicarbonate secretion
c) Decreasing water secretion
d) Inhibiting bile secretion
Explanation: Correct answer is b) Increasing bicarbonate secretion. Secretin enhances duct cell bicarbonate output to neutralize gastric acid.
6. Secretin secretion occurs when:
a) Duodenum is alkaline
b) Duodenum is acidic
c) Duodenum contains fatty acids
d) Duodenum is neutral
Explanation: Correct answer is b) Duodenum is acidic. Acidic pH triggers S-cells to release secretin.
7. CCK acts on pancreas to stimulate:
a) Duct cell secretion
b) Acinar cell enzyme secretion
c) Hormone secretion
d) Electrolyte secretion
Explanation: Correct answer is b) Acinar cell enzyme secretion. CCK activates acinar cells to release digestive enzymes.
8. Secretin helps protect duodenal mucosa by:
a) Stimulating acid secretion
b) Enhancing bicarbonate-rich fluid
c) Increasing motility
d) Releasing digestive enzymes
Explanation: Correct answer is b) Enhancing bicarbonate-rich fluid. This neutralizes acidic chyme and protects mucosa.
9. Pancreozymin is another name for:
a) Secretin
b) Gastrin
c) Cholecystokinin
d) Motilin
Explanation: Correct answer is c) Cholecystokinin. Historically called pancreozymin due to its role in pancreatic enzyme secretion.
10. Secretin secretion peaks when gastric pH is:
a) Above 7
b) 5-6
c) Below 4
d) Neutral
Explanation: Correct answer is c) Below 4. Low pH in the duodenum stimulates maximum secretin release to neutralize acidity.
Topic: Gastrointestinal Physiology
Subtopic: Basic Electrical Rhythm (BER)
Keyword Definitions:
- Pacemaker Cells: Specialized cells that spontaneously generate rhythmic electrical impulses to regulate contraction.
- BER (Basic Electrical Rhythm): Slow, rhythmic depolarizations in gastrointestinal smooth muscles controlling peristalsis.
- Interstitial Cells of Cajal: GI tract cells acting as pacemakers, generating BER and coordinating smooth muscle contractions.
- SA Node: Cardiac pacemaker cells in the right atrium initiating heartbeat.
Lead Question - 2013
Which cells are referred as "Pacemaker cells" with relation to 'BER'?
a) SA node
b) AV node
c) Interstitial cells of Cajal
d) Pyramidal cells
Answer and Explanation:
Correct answer is c) Interstitial cells of Cajal. These specialized GI cells generate spontaneous slow waves, called the basic electrical rhythm (BER), coordinating peristaltic contractions of smooth muscles. They act as pacemakers, unlike SA or AV nodes in the heart, and are crucial for rhythmic gastrointestinal motility.
Guessed Questions for NEET PG:
1. BER is primarily recorded in which part of GI tract?
a) Stomach
b) Duodenum
c) Colon
d) Esophagus
Explanation: Correct answer is a) Stomach. The stomach shows a dominant frequency of BER (~3 cycles/min), initiated by Interstitial cells of Cajal.
2. Interstitial cells of Cajal communicate with smooth muscle via:
a) Chemical synapses
b) Gap junctions
c) Desmosomes
d) Tight junctions
Explanation: Correct answer is b) Gap junctions. Electrical signals generated by ICCs propagate through smooth muscle via gap junctions, coordinating contractions.
3. Slow waves of BER determine:
a) Strength of contraction
b) Frequency of contraction
c) Duration of digestion
d) Secretory activity
Explanation: Correct answer is b) Frequency of contraction. BER sets the rhythm, but not the force, of smooth muscle contraction.
4. Cardiac SA node differs from ICCs in that it:
a) Is found in GI tract
b) Initiates heartbeats
c) Generates BER
d) Connects via gap junctions
Explanation: Correct answer is b) Initiates heartbeats. SA node is the cardiac pacemaker, whereas ICCs generate GI slow waves.
5. ICC deficiency leads to:
a) Enhanced peristalsis
b) Gastric dysrhythmias
c) Increased enzyme secretion
d) Rapid gastric emptying
Explanation: Correct answer is b) Gastric dysrhythmias. Loss or dysfunction of ICCs disrupts BER, leading to impaired GI motility.
6. BER amplitude is influenced by:
a) Hormones and neurotransmitters
b) Only ICCs
c) Blood glucose
d) Oxygen levels
Explanation: Correct answer is a) Hormones and neurotransmitters. Neurotransmitters like acetylcholine increase contraction strength during slow waves.
7. Pyramidal cells are located in:
a) Heart
b) GI tract
c) Cerebral cortex
d) Pancreas
Explanation: Correct answer is c) Cerebral cortex. Pyramidal cells are cortical neurons, not pacemaker cells in GI or heart.
8. AV node acts as:
a) GI pacemaker
b) Secondary cardiac pacemaker
c) Hormone secreting cell
d) Interstitial cell
Explanation: Correct answer is b) Secondary cardiac pacemaker. AV node can generate slower impulses if SA node fails.
9. ICCs are modulated by:
a) Autonomic nervous system
b) Skeletal muscle
c) Bone marrow
d) Skin receptors
Explanation: Correct answer is a) Autonomic nervous system. Sympathetic and parasympathetic inputs alter BER frequency and contractility.
10. Which ion primarily contributes to slow wave depolarization in ICCs?
a) Sodium
b) Calcium
c) Potassium
d) Chloride
Explanation: Correct answer is b) Calcium. Calcium influx through L-type channels in ICCs initiates depolarization underlying BER.
Topic: Gastrointestinal Physiology
Subtopic: Enteric Nervous System (ENS)
Keyword Definitions:
- Myenteric Plexus: Network of neurons located between circular and longitudinal smooth muscle layers of the GI tract controlling motility.
- Gut Motility: Movement of gastrointestinal contents through coordinated contractions of smooth muscles.
- Enteric Nervous System (ENS): "Second brain" of the gut, regulating secretion, blood flow, and motility independently of CNS.
- Hyperacidity: Excessive secretion of gastric acid leading to increased acidity.
Lead Question - 2013
Inhibition of myenteric plexus results in:
a) Hyperacidity
b) Diarrhea
c) Decreased gut motility
d) Increased secretions
Answer and Explanation:
Correct answer is c) Decreased gut motility. The myenteric plexus regulates the tone and rhythmic contractions of GI smooth muscle. Inhibition reduces peristalsis and slows transit of intestinal contents. Secretions may remain unaffected, while motility is primarily impaired, leading to constipation or delayed gastric emptying.
Guessed Questions for NEET PG:
1. The myenteric plexus is also called:
a) Auerbach's plexus
b) Meissner's plexus
c) Submucosal plexus
d) Pacinian plexus
Explanation: Correct answer is a) Auerbach's plexus. It lies between longitudinal and circular muscle layers and controls gut motility.
2. Inhibition of ENS neurotransmitters like acetylcholine leads to:
a) Increased secretion
b) Reduced smooth muscle contraction
c) Diarrhea
d) Vomiting
Explanation: Correct answer is b) Reduced smooth muscle contraction. Cholinergic signaling in myenteric plexus mediates peristalsis, and inhibition reduces motility.
3. Meissner’s plexus primarily controls:
a) Motility
b) Secretions and local blood flow
c) Heart rate
d) Respiration
Explanation: Correct answer is b) Secretions and local blood flow. Submucosal (Meissner) plexus modulates glandular secretions, unlike myenteric plexus which controls motility.
4. Loss of myenteric neurons in achalasia causes:
a) Esophageal dilation
b) Gastric ulcers
c) Increased motility
d) Diarrhea
Explanation: Correct answer is a) Esophageal dilation. Achalasia results from absent myenteric plexus in esophagus, leading to impaired peristalsis and failure of LES relaxation.
5. Which neurotransmitter primarily excites smooth muscle in ENS?
a) Acetylcholine
b) Norepinephrine
c) Dopamine
d) GABA
Explanation: Correct answer is a) Acetylcholine. Cholinergic neurons in myenteric plexus stimulate smooth muscle contraction, promoting peristalsis.
6. Sympathetic stimulation of ENS results in:
a) Increased motility
b) Decreased motility
c) Vomiting
d) Increased secretion
Explanation: Correct answer is b) Decreased motility. Sympathetic input inhibits myenteric plexus activity, reducing peristalsis and slowing intestinal transit.
7. Parasympathetic stimulation of ENS results in:
a) Reduced secretions
b) Increased gut motility
c) Constipation
d) Gastric ulcers
Explanation: Correct answer is b) Increased gut motility. Parasympathetic fibers (vagus) enhance activity of myenteric plexus, stimulating smooth muscle contractions.
8. In Hirschsprung disease, absence of myenteric plexus causes:
a) Diarrhea
b) Constipation
c) Hyperacidity
d) Vomiting
Explanation: Correct answer is b) Constipation. Congenital absence of ganglion cells in myenteric and submucosal plexus leads to tonic contraction and functional obstruction.
9. Which plexus is more important for rhythmic contractions of GI tract?
a) Myenteric plexus
b) Submucosal plexus
c) Cardiac plexus
d) Pulmonary plexus
Explanation: Correct answer is a) Myenteric plexus. It controls smooth muscle tone and frequency of peristalsis throughout the GI tract.
10. Blocking nitric oxide in ENS primarily affects:
a) Smooth muscle relaxation
b) Gastric acid secretion
c) Pancreatic enzyme output
d) Salivary secretion
Explanation: Correct answer is a) Smooth muscle relaxation. Nitric oxide released from inhibitory neurons in myenteric plexus mediates relaxation, essential for coordinated peristalsis.