Synapse. Cutaway computer illustration of a synapse, the junction between two neurons. Synapses transmit electrical signals from one nerve cell to the next. When the signal reaches the synapse it triggers the release of chemicals called neurotransmitters (yellow) from vesicles (round) in the terminal swelling (bulb-shaped) of the presynaptic cell (top). The neurotransmitters cross a microscopic gap called the synaptic cleft and pass through channels (blue) into the receptor nerve cell (bottom), where they trigger an electrical impulse.