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.
Princeton's WordNet(4.00 / 1 vote)Rate this definition: 1  jacket(noun) a short coat. 2  jacket(noun) an outer wrapping or casing. 3  crown, crownwork, jacket, jacket crown, cap(noun) (dentistry) dental appliance consisting of an artificial crown for a broken or decayed tooth. 4  jacket(noun) the outer skin of a potato.