Synapse Coloured Transmission Electron Micrograph TEM of a synapse These transmit oneway signals from one nerve cell to the next The end of the nerve cell known as a terminal bouton that transmits the signal is seen at upper centre green This is a roughly triangular shape and contains cellorganelles At centre a multitude of small circular synaptic vesicles are seen red which contain a neurotransmitter When a signal is transmitted these vesicles are released and cross the microscopic gap known as the synaptic cleft to the next cell seen at lower right In this way the nerve signal is passed on from cell to cell Magnification x at xcm size