Synapses

Neurons communicate with one another in two ways, electrical synapses and chemical synapses. Electrical synapses are less common than chemical synapses and allow neurons to communicate with one another purely via ion exchange. The gap of an electrical synapse is approximately 3 nm wide and is bridged by gap junctions, themselves made up of connexons. These synapses facilitate communication in the nanosecond range - known as ultrafast transmission - and are especially found in areas of the body where response synchrony is required. Chemical synapses are the most common synapse type in the body and are an order of magnitude wider than electrical synapses, spanning ranges of 20 to 50 nm. A variety of chemicals are passed across this synapse type. First, amino acids are rapid transmission small molecules that directly create an excitatory or inhibitory response in the postsynaptic cell. Glutamate is an excitor while glycine, and GABA are inhibitors. Second, amines are slightly larger organic molecules that have an amine group, and include substances such as acetylcholine, dopamine, and epinephrine, that generally act as neuromodulators. Of these, acetylcholine is the only fast transmitter, and also serves as a direct excitor like glutamate. Third, neuropeptides are short polypeptides that act as neuromodulators, affecting how receptors will respond to different neurotransmitters. Neurotransmitter reception can yield a  wide array of effects, ranging from simple inhibitory or excitatory postsynaptic potentials to modulatory effects with many downstream responses. The variety of neurotransmitters and their associated responses is often pinned as playing a strong role in our neural complexity.