a and p chemical synapse

step 1

AP arrives at axon terminal of presynaptic neuron

step 2

voltage gated Ca 2+ channels open, calcium enters axon terminal

step 3

calcium ions enter the neuron, synaptic vesicles release neurotransmitter

step 4 

neurotransmitter diffuses across synaptic cleft, binds to specific receptors on post synaptic membrane

step 5

binding of neurotransmitter opens ion channels, creates graded potentials

step 6

neurotransmitter effects terminated