Weekly Year 2: GIT Physiology Exam - April 10, 2026 (Section

Question 1

Regarding the action of Gastrin, which of the following is true?

Accepted Answer

It stimulates the secretion of gastric acid and pepsinogen — Gastrin is secreted by G cells in the gastric antrum and duodenum; its primary function is to stimulate parietal cells to secrete HCl and chief cells to secrete pepsinogen.

Question 2

Vasoactive Intestinal Peptide (VIP) causes which of the following effects?

Accepted Answer

Relaxation of intestinal smooth muscle and sphincters — VIP is an inhibitory neurotransmitter in the GIT that induces relaxation of smooth muscle and stimulates intestinal and pancreatic secretion.

Question 3

Stimulation of Gastrointestinal Secretion involves which primary neurotransmitter of the parasympathetic nervous system?

Accepted Answer

Acetylcholine — Acetylcholine is the primary excitatory neurotransmitter of the parasympathetic system (vagus nerve) that stimulates almost all GIT secretions.

Question 4

The hormone Secretin is primarily characterized by:

Accepted Answer

Stimulating a bicarbonate-rich pancreatic juice — Secretin is released in response to acid in the duodenum and acts to stimulate the secretion of bicarbonate from the pancreatic ducts to neutralize the acid.

Question 5

Inhibition of the myenteric (Auerbach’s) plexus leads to which of the following?

Accepted Answer

Decreased gastrointestinal motility — The myenteric plexus primarily controls GIT motility; its inhibition leads to decreased tone and contraction frequency.

Question 6

Stimulation of the submucosal (Meissner’s) plexus results in an increase in which of the following?

Accepted Answer

Secretory activity and local blood flow — The submucosal plexus is mainly involved in controlling local secretion, absorption, and local blood flow.

Question 7

Which GIT hormone inhibits gastric emptying to ensure proper fat digestion?

Accepted Answer

Cholecystokinin (CCK) — CCK is secreted in response to fats and proteins; it slows gastric emptying to allow enough time for bile and pancreatic enzymes to process the chyme.

Question 8

Cholecystokinin (CCK) causes contraction of the:

Accepted Answer

Gallbladder — CCK stimulates the gallbladder to contract and the sphincter of Oddi to relax, facilitating bile delivery into the duodenum.

Question 9

The major factor that stimulates the release of Secretin into the bloodstream is:

Accepted Answer

Acidic chyme (pH < 4.5) in the duodenum — The primary trigger for secretin release from S cells in the duodenum is the presence of H+ ions (acidic chyme).

Question 10

It is known that Gastrin secretion is inhibited by:

Accepted Answer

A very low gastric pH (< 1.5) — Gastrin secretion is regulated by a negative feedback loop where high acidity (low pH) inhibits G cells.

Question 11

Which statement about bile is TRUE?

Accepted Answer

Bile salts are essential for fat emulsification — Bile does not contain enzymes; its main role is emulsification of fats via bile salts. It is produced by the liver, not the gallbladder.

Question 12

Which tissue layer provides for primary digestive motility?

Accepted Answer

Muscularis externa — The muscularis externa, consisting of circular and longitudinal muscle layers, is responsible for peristalsis and segmentation.

Question 13

Regarding the swallowing reflex, which of the following is FALSE?

Accepted Answer

It is entirely under voluntary control throughout the esophagus — Only the first stage of swallowing is voluntary; the pharyngeal and esophageal stages are involuntary reflexes.

Question 14

Which of the following is characteristic of segmenting movements in the small intestine?

Accepted Answer

They mix chyme with digestive juices and increase contact with mucosa — Segmentation is a mixing movement characterized by local contractions that help mix food and aid absorption.

Question 15

Tonic contractions are characterized by:

Accepted Answer

Continuous duration (minutes to hours) and maintaining sphincter pressure — Tonic contractions are sustained and found in sphincters and the orad portion of the stomach to maintain pressure/tone.

Question 16

Secretion of saliva increases in all of the following EXCEPT:

Accepted Answer

Sleep — Salivary secretion is minimal during sleep, which contributes to the phenomenon of 'morning breath'.

Question 17

Defecation is a reflex action that is unique because:

Accepted Answer

It can be voluntarily inhibited by the external anal sphincter — The intrinsic and parasympathetic reflexes trigger the urge, but the external anal sphincter (skeletal muscle) provides voluntary control.

Question 18

In the stomach, the presence of HCL is necessary for:

Accepted Answer

Activation of pepsinogen to pepsin — HCl provides the acidic environment necessary to convert inactive pepsinogen into the active enzyme pepsin.

Question 19

A 55-year-old man with destruction of gastric glands. This predisposes him to:

Accepted Answer

Pernicious anemia due to lack of Intrinsic Factor — Gastric parietal cells secrete Intrinsic Factor, which is essential for Vitamin B12 absorption in the ileum. Deficiency causes pernicious anemia.

Question 20

Which statement about the oral phase of digestion is INCORRECT?

Accepted Answer

Significant absorption of nutrients occurs here — Almost no nutrient absorption occurs in the mouth, except for certain lipid-soluble drugs like nitroglycerin.

Question 21

Which of the following is correct regarding the stomach?

Accepted Answer

It secretes intrinsic factor for Vitamin B12 absorption — The stomach secretes Intrinsic Factor. It has three muscle layers (including the oblique layer) and does not secrete trypsin (a pancreatic enzyme).

Question 22

Water transport in the intestine:

Accepted Answer

Is strictly passive, following osmotic gradients — Water moves across the intestinal mucosa entirely via osmosis, following the movement of solutes like NaCl and glucose.

Question 23

Regarding fat digestion and absorption, which of the following is correct?

Accepted Answer

Micelles are formed to transport fats across the brush border — Micelles ferry monoglycerides and fatty acids to the epithelial surface. Once absorbed, they form chylomicrons and enter the lacteals (lymph).

Question 24

Which pancreatic enzyme is responsible for activating other proteases?

Accepted Answer

Trypsin — Trypsinogen is activated to trypsin by enterokinase; trypsin then activates other trypsinogens, chymotrypsinogen, and procarboxypeptidase.

Question 25

Dietary fiber is beneficial because it:

Accepted Answer

Can be fermented by colonic bacteria to produce short-chain fatty acids — Fiber is not digested by human enzymes but is fermented by microbiota into short-chain fatty acids like butyrate, which nourish colonocytes.

Question 26

Which gastric cells secrete Histamine?

Accepted Answer

Enterochromaffin-like (ECL) cells — ECL cells secrete histamine, which then acts on H2 receptors on parietal cells to stimulate HCl secretion.

Question 27

The Migrating Motor Complex (MMC) is inhibited by:

Accepted Answer

Feeding — The MMC is a 'housekeeping' movement that occurs during the inter-digestive (fasting) state and stops immediately upon eating.

Question 28

Which of the following describes the function of colonic microbiota?

Accepted Answer

They synthesize Vitamin K and certain B vitamins — Gut bacteria play vital roles in synthesizing Vitamin K and B12 and processing indigestible fibers.

Question 29

Potentiation in gastric acid secretion refers to:

Accepted Answer

The synergistic effect of Acetylcholine, Gastrin, and Histamine — Potentiation occurs when the combined effect of multiple stimuli (ACh, Gastrin, Histamine) is greater than the sum of their individual effects.

Question 30

Which of the following is the main site of iron absorption?

Accepted Answer

Duodenum — The duodenum and proximal jejunum are the primary sites for the absorption of iron and calcium.

Question 31

The 'Enterogastric Reflex' serves to:

Accepted Answer

Inhibit gastric emptying and secretion when the duodenum is distended — This reflex is triggered by acid, distension, or irritation in the duodenum, causing a slowing of gastric activity to protect the small intestine.

Question 32

Bile salts are mostly reabsorbed in the:

Accepted Answer

Terminal Ileum — The enterohepatic circulation involves the reabsorption of ~95% of bile salts in the terminal ileum via active transport.

Question 33

What is the primary function of the 'Slow Waves' (Basal Electrical Rhythm) in the GIT?

Accepted Answer

To determine the maximum frequency of contractions — Slow waves are rhythmic oscillations in membrane potential; they do not always cause contractions, but they set the pace for when contractions can occur.

Question 34

Which of the following statements about the pancreas is FALSE?

Accepted Answer

Insulin is an exocrine secretion — Insulin is an endocrine hormone secreted into the blood, not an exocrine secretion into the duct system.

Question 35

The Cephalic Phase of gastric secretion is mediated primarily by:

Accepted Answer

The Vagus Nerve — The cephalic phase occurs before food reaches the stomach; it is triggered by sight, smell, or taste and is mediated by the vagus nerve.

Question 36

In the small intestine, glucose absorption is coupled with the transport of:

Accepted Answer

Sodium — Glucose and galactose are absorbed via secondary active transport using the SGLT-1 carrier, which requires sodium.

Question 37

What is the role of the Gastrocolic Reflex?

Accepted Answer

It stimulates mass movements in the colon after a meal — The gastrocolic reflex (and duodenocolic reflex) increases colonic motility and mass movements in response to food entering the stomach.

Question 38

S-cells in the duodenum secrete Secretin. What is the trigger?

Accepted Answer

Low pH (Acid) — Secretin is stimulated by acidity (low pH) in the duodenum.

Question 39

The enzyme Pepsin is most active at which pH?

Accepted Answer

pH 2.0 — Pepsin is a gastric protease and is highly adapted to the acidic environment of the stomach (optimal pH 1.8 - 3.5).

Question 40

Which of the following inhibits gastrin release?

Accepted Answer

Somatostatin — Somatostatin, released by D cells, acts as a 'universal brake' and inhibits the release of gastrin and other hormones.

Question 41

The functional unit of the liver is the:

Accepted Answer

Liver Lobule — The liver lobule is the structural and functional unit, typically hexagonal in shape with a central vein.

Question 42

A patient with a gallstone blocking the common bile duct will likely have difficulty digesting:

Accepted Answer

Fats — Bile is required for fat emulsification; without it, lipase cannot efficiently digest fats, leading to steatorrhea.

Question 43

Where is the 'Satiety Center' located in the brain?

Accepted Answer

Hypothalamus (Ventromedial Nucleus) — The ventromedial nucleus of the hypothalamus is known as the satiety center, while the lateral hypothalamus is the feeding center.

Question 44

The hormone Motilin is responsible for:

Accepted Answer

Initiating the Migrating Motor Complex — Motilin is cyclicly released during fasting and stimulates the MMC to clear the gut of debris.

Question 45

Which of the following prevents the backflow of fecal contents from the colon into the small intestine?

Accepted Answer

Ileocecal valve — The ileocecal valve/sphincter prevents reflux from the cecum into the ileum.

Question 46

Which of the following is an example of an 'Incretin' hormone?

Accepted Answer

Glucagon-like peptide-1 (GLP-1) — GLP-1 and GIP (Glucose-dependent Insulinotropic Peptide) are incretins that stimulate insulin secretion after a meal.

Question 47

Primary peristalsis in the esophagus is initiated by:

Accepted Answer

The swallowing center in the medulla — Primary peristalsis is a continuation of the pharyngeal stage of swallowing, coordinated by the swallowing center.

Question 48

Secondary peristalsis in the esophagus is initiated by:

Accepted Answer

Local distension by a food bolus or reflux — Secondary peristalsis occurs if a bolus gets stuck or if acid refluxes; it is mediated by the enteric nervous system and vagal afferents.

Question 49

Bicarbonate secretion in the small intestine is primarily to:

Accepted Answer

Neutralize acidic chyme from the stomach — Pancreatic and Brunner's gland secretions are alkaline to protect the mucosa and provide a neutral pH for digestive enzymes.

Question 50

Which statement regarding Gastric Inhibitory Peptide (GIP) is true?

Accepted Answer

It is secreted in response to glucose and fat in the small intestine — GIP (also known as Glucose-dependent Insulinotropic Peptide) inhibits gastric activity and stimulates insulin secretion.

Weekly Year 2: GIT Physiology Exam - April 10, 2026 (Section

Questions, Answers & Explanations