On electron microscopy, the neuromuscular junction shows vesicles of acetylcholine (ACh) in the presynaptic terminal. The postsynaptic membrane (motor end plate) contains ACh receptors concentrated in junctional folds. Which type of acetylcholine receptor is found at the neuromuscular junction?
- A Muscarinic (M1)
- B Nicotinic NN receptor (ganglionic type)
- C Nicotinic NM receptor (muscle-type) ✓
- D Muscarinic (M2)
Correct answer: C. Nicotinic NM receptor (muscle-type)
Explanation
The neuromuscular junction contains nicotinic NM (muscle-type) receptors, specifically the pentameric ligand-gated ion channel with the α1β1γδ subunit composition in fetal muscle and α1β1εδ in adult muscle. Binding of ACh opens Na+/K+ channels, generating an end-plate potential. Nicotinic NN receptors are found in autonomic ganglia. Muscarinic receptors (M1–M5, GPCRs) are found on smooth muscle, cardiac muscle, and gland cells innervated by postganglionic parasympathetics.
Reference: BD Chaurasia's Human Anatomy, 8th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
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