starting with a signal reaching the distal end of the presynaptic axon, indicate the correct order of events that occur during transmission at a cholinergic excitatory synapse
1. opening of calcium gates in synaptic knob as nerve signal arrives
2. exocytosis of Ach; diffusion across synaptic cleft
3. binding of Ach to receptors on postsynaptic neuron
4. opening of sodium gates on post-synaptic membrane allowing influx of sodium
5. depolarization of postsynaptic plasma membrane