What is the gap the transmitter crosses called, and how wide is it? · Lobeworks/17

The synaptic cleft, about 20 nm wide.

What is the gap the transmitter crosses called, and how wide is it?

The synaptic cleft, about 20 nm wide. On one side is the presynaptic terminal that releases the transmitter, on the other the postsynaptic membrane dense with receptors. The gap is so narrow that transmitter crosses it by diffusion in microseconds, so almost all of the synaptic delay is spent before release, on calcium entry and vesicle fusion.