Sequences of synapse

One

The neuron synthesizes chemicals that serve as neurotransmitters, either in the cell body or at the end of the axon

Two

Action potentials travel down the axon. At the presynaptic terminal, the depolarization enables calcium to enter the cell. Calcium releases neurotransmitters from the terminals and into the synaptic cleft, the space between the presynaptic and postsynaptic neurons

Three

The released molecules diffuse across the narrow cleft, attach to receptors, and alter the activity of the postsynaptic neuron in any of several ways

Four

The neurotransmitter molecules separate from their receptors

Five

The neurotransmitter molecules may be taken back into the presynaptic neuron for recycling, or they may diffuse away

Six

Some postsynaptic cells send reverse messages to control the further release of neurotransmitters by presynaptic cells