Also known as adrenaline is a hormone and neurotransmitter.
It increases heart rate, contracts blood vessels, dilates air passages and participates in the fight-or-flight response of the sympathetic nervous system. Chemically, epinephrine is a catecholamine, a monoamine produced only by the adrenal glands from the amino acids phenylalanine and tyrosine.
The term adrenaline is derived from the Latin roots ad- and renes and literally means on the kidney, in reference to the adrenal gland’s anatomic location on the kidney.
The Greek roots epi- and nephros have similar meanings, and give rise to epinephrine. The term epinephrine is often shortened to epi in medical jargon. Adrenal extracts containing adrenaline were first obtained by Polish physiologist Napoleon Cybulski in 1895.
These extracts, which he called “nadnerczyna”, contained epinephrine and other catecholamines. Japanese chemist Jokichi Takamine and his assistant Keizo Uenaka independently discovered adrenaline in 1900. In 1901, Takamine successfully isolated and purified the hormone from the adrenal glands of sheep and oxen.
Adrenaline was first synthesized in the laboratory by Friedrich Stolz and Henry Drysdale Dakin, independently, in 1904.Actions in the body:As a hormone, epinephrine acts on nearly all body tissues. Its actions vary by tissue type and tissue expression of adrenergic receptors. For example, epinephrine causes smooth muscle relaxation in the airways, but causes contraction of the smooth muscle that lines most arterioles.
Epinephrine acts by binding to a variety of adrenergic receptors. Adrenaline is a nonselective agonist of all adrenergic receptors, including α₁, α₂, β₁, β₂, and β₃ receptors. Epinephrine’s binding to these receptors triggers a number of metabolic changes. Binding to α-adrenergic receptors inhibits insulin secretion by the pancreas, stimulates glycogenolysis in the liver and muscle, and stimulates glycolysis in muscle.
β-Adrenergic receptor binding triggers glucagon secretion in the pancreas, increased adrenocorticotropic hormone (ACTH) secretion by the pituitary gland, and increased lipolysis by adipose tissue. Together these effects lead to increased blood glucose and fatty acids, providing substrates for energy production within cells throughout the body. In addition to these metabolic changes, epinephrine also leads to broad alterations throughout all organ systems.
Is a term used to describe somebody who appears to be addicted to epinephrine (endogenous) and such a person is sometimes described as getting a “high” from life. The term adrenaline junkie was popularly used in the 1991 movie Point Break to describe individuals who enjoyed dangerous activities (such as extreme sports e.g. BASE jumping) for the adrenaline “rush”. Adrenaline junkies appear to favour stressful activities for the release of epinephrine as a stress response. Doing this may result in physical harm because of the potential danger.
Whether or not the positive response is caused specifically by epinephrine is difficult to determine, as endorphins are also released during the fight-or-flight response to such activities.
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