To outline the process of synaptic transmission:
1. **Neurotransmitter Release**:
- Action potential reaches the axon terminal.
- This triggers the opening of voltage-gated calcium channels.
- Calcium ions enter the axon terminal.
2. **Synaptic Vesicle Fusion**:
- Calcium ions cause synaptic vesicles to move to the presynaptic membrane.
- Vesicles fuse with the membrane and release neurotransmitters into the synaptic cleft.
3. **Neurotransmitter Binding**:
- Neurotransmitters diffuse across the synaptic cleft.
- They bind to specific receptors on the postsynaptic membrane.
4. **Postsynaptic Response**:
- Receptor binding leads to changes in the postsynaptic cell (excitatory or inhibitory).
- This can generate a new action potential in the postsynaptic neuron.
5. **Termination of Signal**:
- Neurotransmitters are either degraded by enzymes in the synaptic cleft or taken back up into the presynaptic neuron (reuptake).
6. **Reuptake and Reuse**:
- Neurotransmitters taken back up can be repackaged into vesicles for reuse.
- The process is ready to start again with a new action potential.
