19 May 2026
USMLE STEP 1 Pharmacology EXAM –150
ACCURATE QUESTIONS WITH CORRECT ANSWER
2026/2027 LATEST EXAM UPDATE GUARANTEE
HIGH PASS MARK
1. Which receptor causes vasoconstriction, pupil dilation, and contraction of urinary/GI
sphincters?
A. β1
B. β2
C. α1
D. M3
Answer: C. α1
Rationale:
α1 receptors (Gq) cause smooth muscle contraction, especially:
Vasoconstriction
Mydriasis (radial muscle contraction)
Increased bladder and GI sphincter tone
2. Which receptor decreases sympathetic outflow and reduces insulin release?
A. α2
B. β1
C. H1
D. M2
Answer: A. α2
Rationale:
α2 receptors are Gi-coupled inhibitory receptors that:
↓ NE release (presynaptic inhibition)
↓ insulin secretion
↓ lipolysis
3. Which receptor increases heart rate and renin release?
A. β1
B. β2
C. D1
D. M3
Answer: A. β1
,19 May 2026
Rationale:
β1 (Gs) stimulation leads to:
↑ HR and contractility
↑ renin release from JG cells
↑ cardiac output
4. Which receptor causes bronchodilation and uterine relaxation?
A. α1
B. β2
C. M2
D. H2
Answer: B. β2
Rationale:
β2 activation causes smooth muscle relaxation:
Bronchodilation
Uterine relaxation (tocolysis)
Vasodilation in skeletal muscle
5. Which muscarinic receptor is responsible for decreased heart rate?
A. M1
B. M2
C. M3
D. M4
Answer: B. M2
Rationale:
M2 receptors (Gi) act on the heart to:
↓ SA node firing → ↓ HR
↓ atrial contractility
6. Which receptor increases gastric acid secretion?
A. H1
B. H2
C. M3
D. D2
Answer: B. H2
,19 May 2026
Rationale:
H2 receptors on parietal cells increase:
cAMP → ↑ gastric acid secretion
7. Which receptor causes miosis, increased secretions, and GI motility?
A. M3
B. M2
C. β2
D. α1
Answer: A. M3
Rationale:
M3 receptors (Gq) mediate parasympathetic effects:
↑ secretions (saliva, tears)
↑ GI motility
Bronchoconstriction
Miosis + accommodation
8. Which receptor is coupled to Gi protein?
A. β2
B. H2
C. α2
D. D1
Answer: C. α2
Rationale:
Gi receptors inhibit adenylate cyclase:
α2, M2, D2 → ↓ cAMP
9. Which drug is used for Alzheimer disease and works by increasing acetylcholine via AChE
inhibition?
A. Atropine
B. Donepezil
C. Salmeterol
D. Phenylephrine
Answer: B. Donepezil
, 19 May 2026
Rationale:
Donepezil is a reversible acetylcholinesterase inhibitor, increasing ACh in CNS → improves cognitive
function in Alzheimer disease.
10. Which drug is used in acute asthma due to β2 agonism?
A. Albuterol
B. Propranolol
C. Atropine
D. Neostigmine
Answer: A. Albuterol
Rationale:
Albuterol is a short-acting β2 agonist (SABA):
Bronchodilation
First-line for acute asthma attacks
11. Which drug is used to reverse neuromuscular blockade and treat myasthenia gravis?
A. Neostigmine
B. Epinephrine
C. Atropine
D. Dopamine
Answer: A. Neostigmine
Rationale:
Neostigmine is an AChE inhibitor:
↑ ACh at neuromuscular junction
Used in MG and post-op ileus
12. Which toxin blocks voltage-gated sodium channels and prevents depolarization?
A. Ciguatoxin
B. Tetrodotoxin
C. Scombroid toxin
D. Histamine
Answer: B. Tetrodotoxin
Rationale:
Tetrodotoxin (pufferfish toxin):
Blocks Na⁺ channels
Prevents action potential initiation
USMLE STEP 1 Pharmacology EXAM –150
ACCURATE QUESTIONS WITH CORRECT ANSWER
2026/2027 LATEST EXAM UPDATE GUARANTEE
HIGH PASS MARK
1. Which receptor causes vasoconstriction, pupil dilation, and contraction of urinary/GI
sphincters?
A. β1
B. β2
C. α1
D. M3
Answer: C. α1
Rationale:
α1 receptors (Gq) cause smooth muscle contraction, especially:
Vasoconstriction
Mydriasis (radial muscle contraction)
Increased bladder and GI sphincter tone
2. Which receptor decreases sympathetic outflow and reduces insulin release?
A. α2
B. β1
C. H1
D. M2
Answer: A. α2
Rationale:
α2 receptors are Gi-coupled inhibitory receptors that:
↓ NE release (presynaptic inhibition)
↓ insulin secretion
↓ lipolysis
3. Which receptor increases heart rate and renin release?
A. β1
B. β2
C. D1
D. M3
Answer: A. β1
,19 May 2026
Rationale:
β1 (Gs) stimulation leads to:
↑ HR and contractility
↑ renin release from JG cells
↑ cardiac output
4. Which receptor causes bronchodilation and uterine relaxation?
A. α1
B. β2
C. M2
D. H2
Answer: B. β2
Rationale:
β2 activation causes smooth muscle relaxation:
Bronchodilation
Uterine relaxation (tocolysis)
Vasodilation in skeletal muscle
5. Which muscarinic receptor is responsible for decreased heart rate?
A. M1
B. M2
C. M3
D. M4
Answer: B. M2
Rationale:
M2 receptors (Gi) act on the heart to:
↓ SA node firing → ↓ HR
↓ atrial contractility
6. Which receptor increases gastric acid secretion?
A. H1
B. H2
C. M3
D. D2
Answer: B. H2
,19 May 2026
Rationale:
H2 receptors on parietal cells increase:
cAMP → ↑ gastric acid secretion
7. Which receptor causes miosis, increased secretions, and GI motility?
A. M3
B. M2
C. β2
D. α1
Answer: A. M3
Rationale:
M3 receptors (Gq) mediate parasympathetic effects:
↑ secretions (saliva, tears)
↑ GI motility
Bronchoconstriction
Miosis + accommodation
8. Which receptor is coupled to Gi protein?
A. β2
B. H2
C. α2
D. D1
Answer: C. α2
Rationale:
Gi receptors inhibit adenylate cyclase:
α2, M2, D2 → ↓ cAMP
9. Which drug is used for Alzheimer disease and works by increasing acetylcholine via AChE
inhibition?
A. Atropine
B. Donepezil
C. Salmeterol
D. Phenylephrine
Answer: B. Donepezil
, 19 May 2026
Rationale:
Donepezil is a reversible acetylcholinesterase inhibitor, increasing ACh in CNS → improves cognitive
function in Alzheimer disease.
10. Which drug is used in acute asthma due to β2 agonism?
A. Albuterol
B. Propranolol
C. Atropine
D. Neostigmine
Answer: A. Albuterol
Rationale:
Albuterol is a short-acting β2 agonist (SABA):
Bronchodilation
First-line for acute asthma attacks
11. Which drug is used to reverse neuromuscular blockade and treat myasthenia gravis?
A. Neostigmine
B. Epinephrine
C. Atropine
D. Dopamine
Answer: A. Neostigmine
Rationale:
Neostigmine is an AChE inhibitor:
↑ ACh at neuromuscular junction
Used in MG and post-op ileus
12. Which toxin blocks voltage-gated sodium channels and prevents depolarization?
A. Ciguatoxin
B. Tetrodotoxin
C. Scombroid toxin
D. Histamine
Answer: B. Tetrodotoxin
Rationale:
Tetrodotoxin (pufferfish toxin):
Blocks Na⁺ channels
Prevents action potential initiation
