Figure 6.1. Electrical synapse. Connexon channels from two cells join to-
gether, forming a pore connecting the cells. Where the two connexons join,
the membranes of the two adjacent cells are separated by a gap of about 3 nm.
Each connexon channel is formed from six connexin subunit proteins, joined
in a doughnut-like fashion with a hole in the center.
The part of the postsynaptic cell with which the axon is connecting
is generally a dendrite, but it could also be the soma or even a part of
the axon of the downstream neuron. If the synapse is with a dendrite,
then it is often with a dendritic spine, a bulge on a dendrite that in-
creases the surface area available for receiving signals.
Within the axon terminal are numerous small spheres formed of