COMSAE Phase 1-Form ASA 104
Foundational Biomedical Sciences Exam
Practice Questions & [Verified Answers],
Plus Explained Rationales|2026 Latest
Update| Instant Download PDF
1. A 22-year-old osteopathic medical student participates in a
physiology experiment. During moderate exercise, skeletal muscle
blood flow increases substantially despite heightened
sympathetic nervous system activity. Which local mediator is
most responsible for overriding sympathetic vasoconstriction in
active skeletal muscle?
A. Endothelin-1
B. Angiotensin II
C. Adenosine
D. Thromboxane A2
Answer: C. Adenosine
Rationale: Active skeletal muscle generates metabolites including
adenosine, CO₂, H⁺, K⁺, and lactate. These substances cause local
vasodilation and override sympathetic vasoconstrictive influences
through functional sympatholysis. Adenosine is a potent vasodilator
that increases tissue perfusion during exercise.
2. A researcher inhibits the enzyme responsible for converting
dihydrofolate to tetrahydrofolate. DNA synthesis subsequently
decreases. Which medication acts through this mechanism?
,A. Hydroxyurea
B. Methotrexate
C. 5-Fluorouracil
D. Cytarabine
Answer: B. Methotrexate
Rationale: Methotrexate inhibits dihydrofolate reductase, preventing
formation of tetrahydrofolate required for thymidine synthesis. This
impairs DNA replication in rapidly dividing cells.
3. A 6-year-old child develops hematuria two weeks after
streptococcal pharyngitis. Electron microscopy reveals
subepithelial immune complex deposits. What is the most likely
diagnosis?
A. Minimal change disease
B. Membranous nephropathy
C. Poststreptococcal glomerulonephritis
D. IgA nephropathy
Answer: C. Poststreptococcal glomerulonephritis
Rationale: Poststreptococcal glomerulonephritis typically occurs 1–3
weeks after streptococcal infection and is characterized by
subepithelial “hump-like” immune complex deposits, hematuria,
hypertension, and edema.
4. A patient presents with proximal muscle weakness, heliotrope
rash, and elevated creatine kinase levels. Histology reveals
perifascicular atrophy. Which diagnosis is most likely?
A. Polymyositis
B. Dermatomyositis
,C. Inclusion body myositis
D. Muscular dystrophy
Answer: B. Dermatomyositis
Rationale: Dermatomyositis is characterized by proximal muscle
weakness, elevated muscle enzymes, heliotrope rash, Gottron
papules, and perifascicular muscle fiber atrophy caused by
complement-mediated vascular injury.
5. A mutation prevents normal migration of neural crest cells into
the distal colon. Which condition develops?
A. Pyloric stenosis
B. Hirschsprung disease
C. Intussusception
D. Meckel diverticulum
Answer: B. Hirschsprung disease
Rationale: Hirschsprung disease results from failure of neural crest
cells to migrate into the bowel wall, producing absence of enteric
ganglion cells and functional obstruction of the distal colon.
6. Which cytokine is primarily responsible for inducing hepatic
production of acute-phase reactants during inflammation?
A. IL-2
B. IL-4
C. IL-6
D. IL-8
Answer: C. IL-6
Rationale: IL-6 stimulates hepatocytes to produce acute-phase
proteins such as CRP, fibrinogen, serum amyloid A, and hepcidin.
, 7. A patient with chronic alcoholism develops confusion,
ophthalmoplegia, and ataxia. Deficiency of which vitamin is
responsible?
A. Vitamin B6
B. Vitamin B12
C. Thiamine
D. Niacin
Answer: C. Thiamine
Rationale: Wernicke encephalopathy results from thiamine deficiency
and presents with confusion, ophthalmoplegia, and ataxia. Untreated
cases may progress to Korsakoff syndrome.
8. Which receptor mediates increased heart rate through activation
of Gs protein and elevated cAMP?
A. α1 receptor
B. β1 receptor
C. M2 receptor
D. D2 receptor
Answer: B. β1 receptor
Rationale: β1-adrenergic receptors activate adenylate cyclase through
Gs proteins, increasing cAMP and enhancing heart rate, contractility,
and conduction velocity.
9. A patient with hyperparathyroidism develops kidney stones.
Which electrolyte abnormality is expected?
A. Hyperkalemia
B. Hypocalcemia
C. Hypercalcemia
D. Hyponatremia
Foundational Biomedical Sciences Exam
Practice Questions & [Verified Answers],
Plus Explained Rationales|2026 Latest
Update| Instant Download PDF
1. A 22-year-old osteopathic medical student participates in a
physiology experiment. During moderate exercise, skeletal muscle
blood flow increases substantially despite heightened
sympathetic nervous system activity. Which local mediator is
most responsible for overriding sympathetic vasoconstriction in
active skeletal muscle?
A. Endothelin-1
B. Angiotensin II
C. Adenosine
D. Thromboxane A2
Answer: C. Adenosine
Rationale: Active skeletal muscle generates metabolites including
adenosine, CO₂, H⁺, K⁺, and lactate. These substances cause local
vasodilation and override sympathetic vasoconstrictive influences
through functional sympatholysis. Adenosine is a potent vasodilator
that increases tissue perfusion during exercise.
2. A researcher inhibits the enzyme responsible for converting
dihydrofolate to tetrahydrofolate. DNA synthesis subsequently
decreases. Which medication acts through this mechanism?
,A. Hydroxyurea
B. Methotrexate
C. 5-Fluorouracil
D. Cytarabine
Answer: B. Methotrexate
Rationale: Methotrexate inhibits dihydrofolate reductase, preventing
formation of tetrahydrofolate required for thymidine synthesis. This
impairs DNA replication in rapidly dividing cells.
3. A 6-year-old child develops hematuria two weeks after
streptococcal pharyngitis. Electron microscopy reveals
subepithelial immune complex deposits. What is the most likely
diagnosis?
A. Minimal change disease
B. Membranous nephropathy
C. Poststreptococcal glomerulonephritis
D. IgA nephropathy
Answer: C. Poststreptococcal glomerulonephritis
Rationale: Poststreptococcal glomerulonephritis typically occurs 1–3
weeks after streptococcal infection and is characterized by
subepithelial “hump-like” immune complex deposits, hematuria,
hypertension, and edema.
4. A patient presents with proximal muscle weakness, heliotrope
rash, and elevated creatine kinase levels. Histology reveals
perifascicular atrophy. Which diagnosis is most likely?
A. Polymyositis
B. Dermatomyositis
,C. Inclusion body myositis
D. Muscular dystrophy
Answer: B. Dermatomyositis
Rationale: Dermatomyositis is characterized by proximal muscle
weakness, elevated muscle enzymes, heliotrope rash, Gottron
papules, and perifascicular muscle fiber atrophy caused by
complement-mediated vascular injury.
5. A mutation prevents normal migration of neural crest cells into
the distal colon. Which condition develops?
A. Pyloric stenosis
B. Hirschsprung disease
C. Intussusception
D. Meckel diverticulum
Answer: B. Hirschsprung disease
Rationale: Hirschsprung disease results from failure of neural crest
cells to migrate into the bowel wall, producing absence of enteric
ganglion cells and functional obstruction of the distal colon.
6. Which cytokine is primarily responsible for inducing hepatic
production of acute-phase reactants during inflammation?
A. IL-2
B. IL-4
C. IL-6
D. IL-8
Answer: C. IL-6
Rationale: IL-6 stimulates hepatocytes to produce acute-phase
proteins such as CRP, fibrinogen, serum amyloid A, and hepcidin.
, 7. A patient with chronic alcoholism develops confusion,
ophthalmoplegia, and ataxia. Deficiency of which vitamin is
responsible?
A. Vitamin B6
B. Vitamin B12
C. Thiamine
D. Niacin
Answer: C. Thiamine
Rationale: Wernicke encephalopathy results from thiamine deficiency
and presents with confusion, ophthalmoplegia, and ataxia. Untreated
cases may progress to Korsakoff syndrome.
8. Which receptor mediates increased heart rate through activation
of Gs protein and elevated cAMP?
A. α1 receptor
B. β1 receptor
C. M2 receptor
D. D2 receptor
Answer: B. β1 receptor
Rationale: β1-adrenergic receptors activate adenylate cyclase through
Gs proteins, increasing cAMP and enhancing heart rate, contractility,
and conduction velocity.
9. A patient with hyperparathyroidism develops kidney stones.
Which electrolyte abnormality is expected?
A. Hyperkalemia
B. Hypocalcemia
C. Hypercalcemia
D. Hyponatremia
