Structure
Each gap junction (aka nexus junction) contains numerous gap junction channels which cross the membranes of both cells. With a lumen diameter of about 1.2 to 2.0 nm, the pore of a gap junction channel is wide enough to allow ions and even medium sized molecules like signaling molecules to flow from one cell to the next, thereby connecting the two cells' cytoplasm. Thus when the voltage of one cell changes, ions may move through from one cell to the next, carrying positive charge with them and depolarizing the postsynaptic cell.
Gap junction funnels are composed of two hemi-channels called connexons in vertebrates, one contributed by each cell at the synapse. Connexons are formed by six 7.5 nm long, four-pass membrane-spanning protein subunits called connexins, which may be identical or slightly different from one another.
Read more about this topic: Electrical Synapse
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