Chemical synapses are either ordepending on how they
affect the membrane potential of the post synaptic Neuron

there is a possibility that the neuron can fire back at the potential neuron.

Explanation:

At a chemical synapses an action of potential triggers the Presynaptic neuron to the postsynaptic neuron either more or less likely to fire its own action of its potential neuron.

you must remain stopped until the stop signal is retracted and the red lights are turned off. approaching traffic in the opposite roadway of a divided highway shall not be required to stop, even if the school bus has the stop-arm extended and the alternately flashing warning signal lamps on.