Synapse

SOURCE: Wikipedia.org

Chemical synapses are specialized junctions through which neurons signal to each other and to non-neuronal cells such as those in muscles or glands. Chemical synapses allow neurons to form interconnected circuits within the central nervous system. They are thus crucial to the biological computations that underlie perception and thought. They provide the means through which the nervous system connects to and controls the other systems of the body, for example the specialized synapse between a motor neuron and a muscle cell is called a neuromuscular junction.

Young children have about 1016 synapses (10 quadrillion). This number declines with age, stabilizing by adulthood. Estimates for adults vary from 1015 to 5 × 1015 (1-5 quadrillion) synapses.

The word "synapse" comes from "synaptein", which Sir Charles Scott Sherrington and colleagues coined from the Greek "syn-" ("together") and "haptein" ("to clasp"). Chemical synapses are not the only type of biological synapse: electrical and immunological synapses exist as well. Without a qualifier, however, "synapse" commonly refers to a chemical synapse.