Describe how a neurotransmitter, such as acetylcholine, is released from a brain cell.

When an action potential reaches the presynaptic bouton, it causes an influx of calcium into the nerve cell ending. This, in turn, causes vesicles containing the neurotransmitter (acetylcholine) to move to and fuse with the presynaptic membrane. Fusion causes the release of acetylcholine into the synaptic cleft, where it can bind to receptors on the post-synaptic bouton. This binding causes sodium channels on the post-synaptic bouton to open, continuing the action potential.Once the reaction has finished, the bound acetylcholine is then broken down by acetylcholinesterase allowing reuptake and recycling back into the presynaptic bouton.