Step 1: action potential arrives at axon terminal Step 2: voltage gated Ca channels open, enter the axon terminal, moving down electrochemical gradient Step 3: Ca entry causes ACh to be released by exocytosis Step 4: ACh diffused across synaptic cleft and binds to ACh receptors on the sarcolemma Step 4: Binding initiates a change in the electrical state of the muscle cell called action potential