Chemical Synapse

 

We see the presynaptic button above and the postsynaptic cell below (use the "distant" view to see it all).

The presynaptic button is one of the terminal parts of the presynaptic nerve cell.

When an electrical stimulatory impulse reaches the presynaptic button, CA++ ions are released into the cell and this triggers the fusion of the vesicles (that are inside the presynaptic button) with the button plasma membrane.

We see here one vesicle already fused and several vesicles that are still not fused.

All vesicles contain neurotransmitter molecules (e.g. Acetylcholine) here shown as red balls. As the vesicles fuse with the membrane, the neurotransmitter molecules are released into the synaptic cleft and for a short time they fuse with the postsynaptic transmitter gated membrane channels (shown here in blue) which then open and lead to the depolarization of the postsynaptic cell.