Neurotransmitters are the nervous system molecules that transmit messages between neurons.

Neurotransmitters impact the “receiving” neuron in one of three ways: “excitatory” (promotes an “action potential” in the receiving neuron); “inhibitory” (prevents the “action potential"); or “modulatory” (they can impact many neurons simultaneously, regulating them).

Neurotransmitters are either amino acids, small amine molecules (there are about 12 of these), or neuropeptides (there are over 100 of these).

Some of the “brain” related neurotransmitters are dopamine, serotonin, melatonin, and adrenaline. You’ve probably heard of them.