events at the neuromuscular junction

1: action potential arrives at axon terminal of motor neuron

voltage-gated calcium channels in a neuron’s synaptic end bulb open

calcium enters the neuron, causing exocytosis of ACh into the synaptic cleft

2: ACh binds to ligand-gated ion channels on motor end plate

Na+ enters muscle and K+ leaves muscle

more Na+ enters than K+ exits, producing a local change in the membrane pot

3: depolarization triggers a muscle action potential

this causes Ca2+ to be released from sarcoplasmic reticulum

4: muscle stimulation is ended when

ACh in synaptic cleft gets broken down by acetylcholinesterase

the events at the NMJ produce

a muscle action potential that causes muscle contraction to occur