Beginning at the synapse of a neuron, place the events in neuronal signaling in the correct sequence. 1. Ion channels bind the ligand and open. 2. Na is pumped out of the cell, and the membrane potential is restored. 3. Acetylcholinesterase breaks down acetylcholine. 4. Na enters the postsynaptic cell, and the membrane potential changes. 5. Acetylcholine is released into the synapse. 6. Na ion channels close.