Inferior to the cortex is the inner medulla. The medulla functions to secrete epinephrine and other catecholamines like norepinephrine and dopamine in smaller concentrations. All catecholamines are synthesized from the precursor amino acid tyrosine.
Epinephrine, also known as adrenaline, is a fast-acting, quick-release hormone that aids in the fight-or-flight immune response and is released in large amounts by the adrenal medulla.
Norepinephrine/noradrenaline is another catecholamine released from the adrenal medulla but in much smaller quantities. It has a similar function to epinephrine and plays a role in sympathetic fight-or-flight responses involving nervous system tissue.
Dopamine is a neurotransmitter and plays a role in the pleasure centers of the brain. When released it makes people feel good, which can become a problem with addiction. Dopamine is important for brain function and development as well as muscle function. Altered levels of dopamine have been linked to schizophrenia and Parkinson's disease. In blood vessels, dopamine antagonizes norepinephrine and is a vasodilator, reduces lymphocyte activity, and reduces insulin secretion from the pancreas.