The space between nerve cells is called a synapse. It is a gap used for communication between nerve cells. To transmit an electrical signal from one nerve cell to another, chemicals are released into the synapse by one nerve cell and picked up by the other nerve cell.
The nerve cell that releases chemicals into the synapse is called the presynaptic neuron; the one that receives the signal is the postsynaptic neuron. The chemicals released into the synapse are neurotransmitters such as acetylcholine and dopamine.
An electrical signal or impulse travels down the axon, or fiber portion, of the presynaptic neuron, causing vesicles in the axon terminals to merge with the cell membrane. This fusion releases neurotransmitters within the vesicles into the synapse. Dendrites, which are fibers that bring messages to a neuron's cell body, take up the neurotransmitters. In a postsynaptic cell, neurotransmitters cause a series of events leading to transmission of the electrical signal down the axon.