Unlike an electrical synapse, the chemical synapses are separated by a space called the synaptic cleft, typically measured between 15 and 25 nm. Transmission of an excitatory signal involves several steps outlined below.
Definition of cap. 1  1a : a head covering especially with a visor and no brimb : a distinctive head covering emblematic of a position or office: such as (1) : a cardinal's biretta (2) : mortarboard.
a fine head of hair. 16 the source or origin of a river or stream. 17 cap when part of name a headland or promontory, esp. a high one. 18 the obverse of a coin, usually bearing a portrait of the head or a full figure of a monarch, deity, etc.