Neurotransmitters are chemical messengers. They send information between neurons by crossing a synapse. Electrical signals are not able to cross the gap between most neurons. They are changed into chemical signals to cross the gap. Neurotransmitters act mostly on chemical synapses. Once they reach the next neuron they are absorbed. The neuron then changes this chemical signal back into an electrical signal called an action potential. The action potential passes across the next neuron and to the next synapse.