a) When an action potential arrives at the presynaptic membrane there is an influx of calcium ions which allows the vesicles containing neurotransmitter to move to and fuse with the presynaptic membrane. The neurotransmitter is released and diffuses across the synaptic cleft binding to voltage gated channels on the post synaptic membrane allowing sodium ions to enter and generate an action potential.b) Includes steps of depolarization and repolarizationc) mentions difference in error bars - if no overlap difference is significant