Neuromuscular Transmission

Key points

• • At the neuromuscular junction, the nerve signal is passed to the muscle by the chemical messenger acetylcholine.
• • When the nerve impulse arrives, calcium enters the nerve ending and triggers the release of acetylcholine into the gap.
• • Acetylcholine binds receptors on the muscle, opening channels that let the muscle membrane depolarise and fire its own impulse.
• • The enzyme acetylcholinesterase quickly breaks down acetylcholine, so the signal is brief and the muscle can relax.
• • This junction is the target of disease and drugs: myasthenia gravis blocks the receptors, and muscle relaxants and some poisons act here.