Catecholamines are molecules that have a catechol nucleus
Nucleus may refer to:*Atomic nucleus, the very dense region at the center of an atom*Cell nucleus, the control center of a cell, which contains the cell's chromosomal DNA*Nucleus , a cluster of neurons in the central nervous system...

consisting of benzene
Benzene is an organic chemical compound. It is composed of 6 carbon atoms in a ring, with 1 hydrogen atom attached to each carbon atom, with the molecular formula C6H6....

 with two hydroxyl
A hydroxyl is a chemical group containing an oxygen atom covalently bonded with a hydrogen atom. In inorganic chemistry, the hydroxyl group is known as the hydroxide ion, and scientists and reference works generally use these different terms though they refer to the same chemical structure in...

 side groups and a side-chain amine. They include dopamine
Dopamine is a catecholamine neurotransmitter present in a wide variety of animals, including both vertebrates and invertebrates. In the brain, this substituted phenethylamine functions as a neurotransmitter, activating the five known types of dopamine receptors—D1, D2, D3, D4, and D5—and their...

, as well as the "fight-or-flight"
Fight-or-flight response
The fight-or-flight response was first described by Walter Bradford Cannon....

 hormones adrenaline (epinephrine in US English) and noradrenaline (norepinephrine in US English) released by the adrenal medulla
Adrenal medulla
The adrenal medulla is part of the adrenal gland. It is located at the center of the gland, being surrounded by the adrenal cortex. It is the innermost part of the adrenal gland, consisting of cells that secrete epinephrine , norepinephrine , and a small amount of dopamine in response to...

 of the adrenal glands in response to stress.

They are called catecholamines because they contain a catechol or 3,4-dihydroxybenzene group.