Which of the following IS NOT true about the roles of chemical synapses and their neurotransmitters? Some bind with the postsynaptic cell and interrupt its firing, which is called an inhibitory response.

Some bind with the postsynaptic cell and cause the firing this second cell, which is called an excitatory response.

Some are only electrical, so no neurotransmitters are necessary in these chemical synapses.

One hundred or more types of neurotransmitters have been identified, and they have different excitatory and inhibitory effects.