A neurotransmitter is a chemical in the brain that helps regulate the electrical signals between neurons. Neurotransmitters exist in little pockets, inside the nerve cells, called vesicles. When an electrical signal triggers the neuron, these vesicles float to the cell membrane and release their neurotransmitters. The neurotransmitters then jump across the synapse and bind to receptors on adjacent neurons.
How the adjacent neuron reacts to the neurotransmitters depends on a number of factors. There are many different types of neurotransmitters produce different results. Some cause the adjacent neuron to trigger and others suppress triggering. It is the combined effect of all the neurotransmitters that determines what happens to the signal.
