MCQ on Adrenaline & Acetylcholine Mechanism – MCQs on ANS Pharmacology

Adrenaline & Acetylcholine Mechanism – MCQs

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1. Adrenaline primarily acts through which type of receptors?

A. Muscarinic
B. Nicotinic
C. Adrenergic
D. Dopaminergic
Answer: ✅ C. Adrenergic
Explanation: Adrenaline binds to alpha and beta adrenergic receptors.

2. Which adrenergic receptor subtype causes vasoconstriction?

A. β1
B. β2
C. α1
D. α2
Answer: ✅ C. α1
Explanation: α1 receptors mediate vasoconstriction via Gq pathway.

3. β2 receptor stimulation by adrenaline causes:

A. Bronchoconstriction
B. Bradycardia
C. Bronchodilation
D. Miosis
Answer: ✅ C. Bronchodilation
Explanation: β2 activation relaxes bronchial smooth muscles.

4. Which second messenger is increased by β1 receptor activation?

A. IP₃
B. DAG
C. cAMP
D. cGMP
Answer: ✅ C. cAMP
Explanation: β1 uses Gs → ↑ cAMP → ↑ heart rate & contractility.

5. Which G-protein is coupled with α1 receptors?

A. Gi
B. Gs
C. Gq
D. Gt
Answer: ✅ C. Gq
Explanation: α1 → Gq → ↑ IP₃/DAG → ↑ Ca²⁺

6. Acetylcholine acts on which type of receptors at the neuromuscular junction?

A. α1
B. β1
C. Muscarinic
D. Nicotinic Nm
Answer: ✅ D. Nicotinic Nm
Explanation: Nm receptors on skeletal muscle are ligand-gated Na⁺ channels.

7. Which of the following is a muscarinic receptor effect?

A. Increased heart rate
B. Bronchodilation
C. Decreased GI motility
D. Increased glandular secretion
Answer: ✅ D. Increased glandular secretion
Explanation: M3 receptor activation increases exocrine secretions.

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8. M2 receptor activation causes:

A. Bronchodilation
B. Increased heart rate
C. Decreased heart rate
D. Muscle paralysis
Answer: ✅ C. Decreased heart rate
Explanation: M2 (Gi) → ↓ cAMP → ↓ HR & contractility

9. What is the mechanism of nicotinic receptor activation?

A. G-protein activation
B. Tyrosine kinase pathway
C. Ion channel opening
D. cAMP increase
Answer: ✅ C. Ion channel opening
Explanation: Nicotinic receptors are ligand-gated ion channels.

10. Which of the following effects is NOT mediated by acetylcholine?

A. Miosis
B. Bradycardia
C. Bronchodilation
D. Increased GI motility
Answer: ✅ C. Bronchodilation
Explanation: ACh causes bronchoconstriction via M3.

11. The predominant second messenger in α2 receptor signaling is:

A. ↑ IP₃
B. ↑ cAMP
C. ↓ cAMP
D. ↑ cGMP
Answer: ✅ C. ↓ cAMP
Explanation: α2 is Gi-coupled, inhibits adenylyl cyclase → ↓ cAMP.

12. Which receptor is responsible for positive inotropic and chronotropic effects of adrenaline?

A. β2
B. β1
C. α2
D. M2
Answer: ✅ B. β1
Explanation: β1 increases heart rate and force of contraction.

13. Acetylcholine causes smooth muscle contraction through:

A. M1
B. M2
C. M3
D. Nm
Answer: ✅ C. M3
Explanation: M3 (Gq) increases Ca²⁺, leading to contraction.

14. Which of the following is not a feature of adrenaline action?

A. Tachycardia
B. Increased BP
C. Bronchodilation
D. Increased salivation
Answer: ✅ D. Increased salivation
Explanation: Increased salivation is a parasympathetic (ACh-mediated) effect.

15. Nicotinic Nn receptors are located in:

A. Skeletal muscle
B. Cardiac muscle
C. Autonomic ganglia
D. Endothelium
Answer: ✅ C. Autonomic ganglia
Explanation: Nn receptors are in autonomic ganglia and CNS.