Norepinephrine is a hormone and neurotransmitter that plays a crucial role in the human body. It is synthesized by the adrenal glands and nerve cells in the brain and acts as a stimulant when released into the bloodstream. There are several synonyms for norepinephrine, which include noradrenaline, L-noradrenaline, levarterenol, and 4-(2-Amino-1-hydroxyethyl)-1,2-benzenediol. These terms are often used interchangeably and refer to the same molecule. Norepinephrine is involved in the fight or flight response, regulating heart rate, blood pressure, and stress levels. It is also important in mood regulation and has been implicated in various psychiatric disorders, including depression and anxiety.