Norepinephrine ( INN ) ( abbreviated norepi or NE ), or noradrenaline ( BAN ) ( abbreviated NA, NAd, or norad ), is a catecholamine with multiple roles including as a hormone and a neurotransmitter. Areas of the body that produce or are affected by norepinephrine are described as noradrenergic. The terms noradrenaline ( from the Latin ) and norepinephrine ( derived from Greek ) are interchangeable, with noradrenaline being the common name in most parts of the world. However, to avoid confusion and achieve consistency, medical authorities have promoted norepinephrine as the favoured nomenclature, and this is the term used throughout this article. One of the most important functions of norepinephrine is its role as the neurotransmitter released from the sympathetic neurons affecting the heart. An increase in norepinephrine from the sympathetic nervous system increases the rate of contractions. As a stress hormone, norepinephrine affects parts of the brain, such as the amygdala, where attention and responses are controlled. Along with epinephrine, norepinephrine also underlies the fight-or-flight response, directly increasing heart rate, triggering the release of glucose from energy stores, and increasing blood flow to skeletal muscle. It increases the brain"s oxygen supply. Norepinephrine can also suppress neuroinflammation when released diffusely in the brain from the locus coeruleus. When norepinephrine acts as a drug, it increases blood pressure by increasing vascular tone ( tension of vascular smooth muscle ) through α-adrenergic receptor activation; a reflex bradycardia homeostatic baroreflex is overcome by a compensatory reflex preventing an otherwise inevitable drop in heart rate to maintain blood pressure. Norepinephrine is synthesized from dopamine by dopamine β-hydroxylase in the secretory granules of the medullary chromaffin cells. It is released from the adrenal medulla into the blood as a hormone, and is also a neurotransmitter in the central nervous system and sympathetic nervous system, where it is released from noradrenergic neurons in the locus coeruleus. The actions of norepinephrine are carried out via the binding to adrenergic receptors. Epinephrine ( also known as adrenaline or adrenalin ) is a hormone and a neurotransmitter. Epinephrine has many functions in the body, regulating heart rate, blood vessel and air passage diameters, and metabolic shifts; epinephrine release is a crucial component of the fight-or-flight response of the sympathetic nervous system. In chemical terms, epinephrine is one of a group of monoamines called the catecholamines. It is produced in some neurons of the central nervous system, and in the chromaffin cells of the adrenal medulla from the amino acids phenylalanine and tyrosine. Dopamine ( abbreviated as DA ), a simple organic chemical in the catecholamine family, is a monoamine neurotransmitter which plays a number of important physiological roles in the bodies of animals. In addition to being a catecholamine and a monoamine, dopamine may be classified as a substituted phenethylamine. Its name derives from its chemical structure, which consists of an amine group ( NH2 ) linked to a catechol structure called dihydroxyphenethylamine, the decarboxylated form of dihydroxyphenylalanine ( acronym DOPA ). In the brain, dopamine functions as a neurotransmitter-a chemical released by nerve cells to send signals to other nerve cells. The human brain uses five known types of dopamine receptors, labeled D1, D2, D3, D4, and D5. Dopamine is produced in several areas of the brain, including the substantia nigra and the ventral tegmental area.