What is a synapse and what role do neurotransmitters play?

Firstly, you need to understand where a synapse is and the structure of a neuron (a basic diagram of a neuron could be useful).The brain is made up of a type of cell called a neuron and there are thought to be a100 billion of them in a single brain! Each neuron can be connected to hundreds or thousands of other neurons, meaning that they can create a really complex network really quickly. When we think about synapses, we are thinking about how these neurons communicate with each other. Synapses form between two cells, between the end of one cell's axon (called the pre-synaptic terminal), and the start of another's dendrite (called the post-synaptic terminal). What is a synapse? (Again, a diagram would be great, but this time a diagram of a basic synapse)So it's the point where two neurons get really really close, but do not touch. The fact that they don't touch is really important because it means that there is a space for neurotransmitters to diffuse. The size of the gap between neurons is 20nm and is called the synaptic cleft - to put in context, this is one millionth of a metre, so tiny. Neurotransmitters - what are they, examples and what they do in a synapse. Neurotransmitters are the chemicals that diffuse across a synapse, and there are lots of different types, dividing into excitatory and inhibitory in their effects. Examples of neurotransmitters are serotonin, acetylcholine and dopamine (there are many more but I would suggest learning 3).At a synapse, neurotransmitters are stored in vesicles and when an electrical impulse reaches a synapse, the vesicles fuse with the membrane of the pre-synaptic axon to release the neurotransmitters. As I said before, the neurotransmitters diffuse across the synaptic cleft, and then they reach receptors on the post-synaptic terminal.  The receptors are key for the effect that the neurotransmitter has on the other neuron.