What's the difference between neuromodulators and neurotransmitters?

Neuromodulators modulate regions or circuits of the brain. That is, they affect a group of neurons, causing a modulation of that group.
In contrast, neurotransmitters affect one other neuron. Their action can be described as a neuron-neuron exchange of information, rather than an action on specific postsynaptic neurons. Therefore neuromodulators differ from neurotransmitters, from the point of view of their defining actions. But many neuromodulators do also act as neurotransmitters. A group of neuromodulater is called a ganglion and there are 32 pairs of ganglion throughtout your body that control all of your autonomic and somatic actions.


Neurotransmitters are chemicals that are used to relay, amplify and modulate electrical signals between a neuron and another cell. According to the prevailing beliefs of the 1960s, a chemical can be classified as a neurotransmitter if it meets the following conditions:
It is synthesized endogenously, that is, within the presynaptic neuron;
It is available in sufficient quantity in the presynaptic neuron to exert an effect on the postsynaptic neuron;
Externally administered, it must mimic the endogenously-released substance; and
A biochemical mechanism for inactivation must be present.