Nerve synapse. Artwork of a nerve impulse being passed across the junction, or synapse, between two nerve cells (neurons). As the electrical signal reaches the presynaptic end of a neuron it triggers vesicles (pink), to release neurotransmitters (red and yellow) across the gap, or synaptic cleft, between the two cells. The neurotransmitters bind to receptors (holes) on the postsynaptic membrane, changing the membrane's excitability and triggering an electrical impulse. Mitochondria (green) produce a cell's energy. Other nerve cell bodies are in the background. They have purple nuclei and many dendrites (projections).