Chemical messenger released from the neuron that are involved in all types of behavior/activity?

Not sure exactly what the question is here, but, in general, neurotransmitters (chemicals released from the ends of neurons) are involved in most of behaviors/activities. There are numerous neurotransmitters working in an incredibly complex system of initiating, modifying (amplifying/dampening), and ending messages. Even the "simplest" responses are the effect of millions of these chemical and electrical reactions.