PCB 3703 Exam 3 V3 | PCB 3703 Human
Physiology | Actual Q&A with Rationale (PCB3703
Exam 3) | University of Central Florida
1. Which hormone is primarily responsible for stimulating the contraction of the gallbladder
and the release of pancreatic enzymes?
A. Secretin
B. Gastrin
C. Motilin
D. Cholecystokinin (CCK)
Correct Answer: D
Explanation: Cholecystokinin (CCK) is secreted by I cells in the duodenum in response to
fatty acids and amino acids. It acts to contract the gallbladder while simultaneously
relaxing the Sphincter of Oddi to allow bile into the small intestine. This hormone also
triggers the acinar cells of the pancreas to secrete digestive enzymes.
2. In the parietal cells of the stomach, which enzyme is responsible for the formation of
carbonic acid from CO2 and water?
A. Carbonic anhydrase
B. Pepsin
C. H+/K+ ATPase
,D. Enterokinase
Correct Answer: A
Explanation: Carbonic anhydrase catalyzes the reversible reaction between carbon
dioxide and water to form carbonic acid. This acid then dissociates into bicarbonate and
hydrogen ions, providing the H+ needed for gastric acid secretion. This mechanism is
essential for maintaining the highly acidic environment required for protein denaturation.
3. What is the primary function of the interstitial cells of Cajal in the gastrointestinal tract?
A. Secretory function
B. Pacemaker activity for slow waves
C. Absorption of lipids
D. Immune surveillance
Correct Answer: B
Explanation: Interstitial cells of Cajal function as the electrical pacemakers for smooth
muscle cells in the GI tract. They generate slow waves, which are spontaneous oscillations
in membrane potential that determine the rhythm of contractions. These waves must
exceed a certain threshold to trigger action potentials and resulting muscular contraction.
4. Which of the following is the major site for the absorption of vitamin B12?
A. Duodenum
B. Ileum
, C. Stomach
D. Jejunum
Correct Answer: B
Explanation: Vitamin B12 absorption occurs specifically in the terminal ileum via
receptor-mediated endocytosis. For this process to occur, B12 must be bound to intrinsic
factor, which is secreted by the gastric parietal cells. Failure of this absorption pathway
often leads to pernicious anemia.
5. During the absorptive state, which hormone dominates the metabolic profile to promote
energy storage?
A. Insulin
B. Glucagon
C. Epinephrine
D. Cortisol
Correct Answer: A
Explanation: Insulin is the primary anabolic hormone that levels rise during the fed or
absorptive state. It promotes the uptake of glucose into muscle and adipose tissue while
stimulating glycogenesis and lipogenesis. Its actions are essential for lowering blood
glucose levels after a meal.
Physiology | Actual Q&A with Rationale (PCB3703
Exam 3) | University of Central Florida
1. Which hormone is primarily responsible for stimulating the contraction of the gallbladder
and the release of pancreatic enzymes?
A. Secretin
B. Gastrin
C. Motilin
D. Cholecystokinin (CCK)
Correct Answer: D
Explanation: Cholecystokinin (CCK) is secreted by I cells in the duodenum in response to
fatty acids and amino acids. It acts to contract the gallbladder while simultaneously
relaxing the Sphincter of Oddi to allow bile into the small intestine. This hormone also
triggers the acinar cells of the pancreas to secrete digestive enzymes.
2. In the parietal cells of the stomach, which enzyme is responsible for the formation of
carbonic acid from CO2 and water?
A. Carbonic anhydrase
B. Pepsin
C. H+/K+ ATPase
,D. Enterokinase
Correct Answer: A
Explanation: Carbonic anhydrase catalyzes the reversible reaction between carbon
dioxide and water to form carbonic acid. This acid then dissociates into bicarbonate and
hydrogen ions, providing the H+ needed for gastric acid secretion. This mechanism is
essential for maintaining the highly acidic environment required for protein denaturation.
3. What is the primary function of the interstitial cells of Cajal in the gastrointestinal tract?
A. Secretory function
B. Pacemaker activity for slow waves
C. Absorption of lipids
D. Immune surveillance
Correct Answer: B
Explanation: Interstitial cells of Cajal function as the electrical pacemakers for smooth
muscle cells in the GI tract. They generate slow waves, which are spontaneous oscillations
in membrane potential that determine the rhythm of contractions. These waves must
exceed a certain threshold to trigger action potentials and resulting muscular contraction.
4. Which of the following is the major site for the absorption of vitamin B12?
A. Duodenum
B. Ileum
, C. Stomach
D. Jejunum
Correct Answer: B
Explanation: Vitamin B12 absorption occurs specifically in the terminal ileum via
receptor-mediated endocytosis. For this process to occur, B12 must be bound to intrinsic
factor, which is secreted by the gastric parietal cells. Failure of this absorption pathway
often leads to pernicious anemia.
5. During the absorptive state, which hormone dominates the metabolic profile to promote
energy storage?
A. Insulin
B. Glucagon
C. Epinephrine
D. Cortisol
Correct Answer: A
Explanation: Insulin is the primary anabolic hormone that levels rise during the fed or
absorptive state. It promotes the uptake of glucose into muscle and adipose tissue while
stimulating glycogenesis and lipogenesis. Its actions are essential for lowering blood
glucose levels after a meal.
