Explain the process of synaptic transmission

When the action potential reaches the presynaptic knob, it causes calcium ion protein channels to open and calcium ions enter the presynaptic knob by facilitated diffusion.The increased concentration of the calcium ions causes synaptic vesicles which contain neurotransmitter to fuse with the presynaptic membrane, releasing the neurotransmitter into the synaptic cleft.The neurotransmitter then diffuses across the synaptic cleft and binds to receptors on the postsynaptic membrane, causing sodium ion protein channels on the postsynaptic membrane to open.Sodium ions diffuse into the postsynaptic neurone, generating a new action potential.The neurotransmitter that was bound to the receptors on the postsynaptic membrane is then broken down by enzymes and returned to the presynaptic knob.