Step
Before the spike the step function persists at base-line value, 0. After the spike the wave form's response height increases by a constant amount for a specific number of iterations or time-steps called the response time. After the response time has passed the function returns to its base-line value.
Response Height
The value by which the strength of the synapse is scaled to determine the post synaptic response.
Response Time
The amount of time the post-synaptic response impinges on the post-synaptic cell.