Describe the process of synaptic transmission

In order to move and process sensory information electrical signals are sent around the body via specialised cells called neurones. Signals are transmitted between neurones across structures called synapses. A synapse is made up of a pre-synaptic neurone, a synaptic cleft and a post-synaptic neurone. Neurotransmission begins when an electrical impulse called an action potential arrives at the axon terminal of the pre-synaptic neurone.
The action potential itself cannot travel across the synapse, but it will excite the neurone causing voltage-gated calcium channels to open. The influx of calcium ions causes membrane-bound vesicles within the axon terminal to move and fuse with the pre-synaptic membrane. These vesicles contain substances called neurotransmitters that upon binding are released into the synaptic cleft. Neurotransmitters diffuse across the synapse and will bind to receptors on the post-synaptic membrane, this will cause an effect on the post-synaptic neurone. Neurotransmitters can be excitatory meaning they initiate an action potential in the post-synaptic neurone, or inhibitory preventing an action potential in the post-synaptic neurone. A key neurotransmitter to remember is acetylcholine. Once the neurotransmitter has done its job it needs to be broken down by an enzyme such as acetylcholinesterase to prevent a continuous action potential.
The neuromuscular junction is a special type of synapse that occurs between a neurone and a muscle fibre rather than two neurones. The neurotransmitter here is acetylcholine and it is always excitatory.