Gap junction

Gap junction channels link two cells together via electrical synapses. In an electrical synapse, either neurone can excite the other and is therefore known as bidirectional. The speed of conduction across an electrical synapse is much quicker than that across a chemical synapse as the cytoplasm is continuous between the cells. The presynaptic cell also does not have to reach a threshold potential in order to trigger an action potential in the postsynaptic cell, instead a depolarisation is triggered in the postsynaptic cell that is proportional to the electrical current from the presynaptic cell. 

Gap channels are composed of two hemichannels, where one hemichannel is situated in each opposed cell. Many thousand gap junction channels can make up an electrical synapse.