Which statement about skeletal muscle response to cholinergic activity is accurate?

Which statement about skeletal muscle response to cholinergic activity is accurate?

• A. NOTHING since Post-Ganglionic Receptors are for Epinephrine and Norepinephrine
• B. Increases acetylcholine release
• C. Causes fasciculations
• D. Causes muscle weakness

Answer: (A)

Skeletal muscle contraction is driven by acetylcholine acting on nicotinic acetylcholine receptors at the neuromuscular junction. This somatic pathway is separate from autonomic postganglionic receptors, which typically respond to epinephrine or norepinephrine. As a result, the idea that nothing happens because postganglionic receptors are for catecholamines doesn’t fit the true mechanism: ACh released from the motor neuron binds to nicotinic receptors on the muscle fiber, opening ion channels, depolarizing the muscle membrane, and triggering contraction. The other statements describe contexts that can occur under certain conditions (for example, increasing ACh in the cleft with inhibitors, or producing fasciculations or weakness with excessive or prolonged cholinergic activity), but the primary and consistent response of skeletal muscle to cholinergic activity is contraction via the nicotinic receptor at the neuromuscular junction.

Skeletal muscle contraction is driven by acetylcholine acting on nicotinic acetylcholine receptors at the neuromuscular junction. This somatic pathway is separate from autonomic postganglionic receptors, which typically respond to epinephrine or norepinephrine. As a result, the idea that nothing happens because postganglionic receptors are for catecholamines doesn’t fit the true mechanism: ACh released from the motor neuron binds to nicotinic receptors on the muscle fiber, opening ion channels, depolarizing the muscle membrane, and triggering contraction. The other statements describe contexts that can occur under certain conditions (for example, increasing ACh in the cleft with inhibitors, or producing fasciculations or weakness with excessive or prolonged cholinergic activity), but the primary and consistent response of skeletal muscle to cholinergic activity is contraction via the nicotinic receptor at the neuromuscular junction.