Which receptor type is activated at the neuromuscular junction?

Which receptor type is activated at the neuromuscular junction?

• A. Dopaminergic
• B. Nicotinic
• C. Adrenergic
• D. Muscarinic

Answer: (B)

At the neuromuscular junction, acetylcholine binds to nicotinic acetylcholine receptors on the motor end plate. These receptors are ligand-gated ion channels, so their opening lets sodium (and some potassium) to flow, quickly depolarizing the muscle membrane and producing an end-plate potential. If that depolarization is strong enough, it triggers a muscle action potential and contraction. This fast, direct excitation is the hallmark of nicotinic receptors at the NMJ. In contrast, muscarinic receptors are slower, G protein–coupled receptors found in parasympathetic targets; adrenergic receptors respond to norepinephrine/epinephrine; dopaminergic receptors respond to dopamine. The NMJ uses nicotinic receptors specifically for rapid signaling leading to muscle contraction.

At the neuromuscular junction, acetylcholine binds to nicotinic acetylcholine receptors on the motor end plate. These receptors are ligand-gated ion channels, so their opening lets sodium (and some potassium) to flow, quickly depolarizing the muscle membrane and producing an end-plate potential. If that depolarization is strong enough, it triggers a muscle action potential and contraction. This fast, direct excitation is the hallmark of nicotinic receptors at the NMJ. In contrast, muscarinic receptors are slower, G protein–coupled receptors found in parasympathetic targets; adrenergic receptors respond to norepinephrine/epinephrine; dopaminergic receptors respond to dopamine. The NMJ uses nicotinic receptors specifically for rapid signaling leading to muscle contraction.