A synapse is a functional gap or intercellular space between neural cells (neurons). The neural synapse is bound by the presynaptic terminal end of one neuron, and the dendrite of the postsynaptic neuron. Neuromuscular synapses are created when neurons terminate on a muscle. Neuroglandular synapses occur when neurons terminate on a gland. The major types of neural synapses include axodendritic synapses, axosomatic synapses, and axoaxonic synapses--each corresponding to the termination point of the presynaptic neuron.

The synapse is more properly described in structural terms as a synaptic cleft. The cleft is filled with extra cellular fluid and free neurotransmitters.

Nerve impulses are transmitted through the synaptic gap via chemical messengers--a special group of chemicals termed neurotransmitters. The arrival of an action potential (a moving wave of electrical changes resulting from rapid exchanges of ions across the neural cell membrane) at the presynaptic terminus of a neuron, expels synaptic...