epinephrine

Biology

(noun)

(adrenaline) an amino acid-derived hormone secreted by the adrenal gland in response to stress

Related Terms

  • adrenergic
  • protein kinase A
  • estrogen
  • corticosteroid
  • aldosterone
  • cyclic adenosine monophosphate
  • glucocorticoid
  • catecholamine
  • oxytocin
  • norepinephrine
  • adrenocorticotropic hormone
  • mineralocorticoid
Psychology

(noun)

A hormone, and a neurotransmitter, that regulates heart rate, blood vessel and air passage diameters, and metabolic shifts and that is a crucial component of the fight-or-flight response of the sympathetic nervous system.

Related Terms

  • proprioceptive
  • autonomic
  • visceral
  • subcortical
  • thalamus

Examples of epinephrine in the following topics:

  • Epinephrine and Norepinephrine

    • As a hormone and neurotransmitter, epinephrine acts on nearly all body tissues.
    • Epinephrine acts by binding to a variety of adrenergic receptors.
    • Epinephrine is a nonselective agonist of all adrenergic receptors, including the major subtypes α1, α2, β1, β2, and β3.
    • Epinephrine and norepinephrine are released by the adrenal medulla and nervous system respectively.
    • Kidney function is halted temporarily by epinephrine and norepinephrine.
  • Adrenergic Neurons and Receptors

    • The adrenergic receptors (or adrenoceptors) are a class of metabotropic G protein-coupled receptors that are targets of the catecholamines, especially norepinephrine or noradrenaline, as seen in , and epinephrine (adrenaline) as shown in ).
    • Adrenaline (epinephrine) reacts with both α and βadrenoreceptors, causing vasoconstriction and vasodilation, respectively.
    • Although α receptors are less sensitive to epinephrine, when activated, they override the vasodilation mediated by βadrenoreceptors.
    • The result is that high levels of circulating epinephrine cause vasoconstriction.
    • At lower levels of circulating epinephrine, βadrenoreceptor stimulation dominates, producing an overall vasodilation.
  • Overview of the Adrenal Glands

    • They are chiefly responsible for releasing hormones in response to stress through the synthesis of corticosteroids such as cortisol and catecholamines such as epinephrine.
    • The cortex mainly produces cortisol, aldosterone and androgens, while the medulla chiefly produces epinephrine and norepinephrine.
    • It secretes approximately 20% norepinephrine and 80% epinephrine.
    • Cortisol also promotes epinephrine synthesis in the medulla.
  • Hormonal Regulation of Stress

    • The hormones epinephrine (also known as adrenaline) and norepinephrine (also known as noradrenaline) are released by the adrenal medulla.
    • Epinephrine and norepinephrine increase blood glucose levels by stimulating the liver and skeletal muscles to break down glycogen and by stimulating glucose release by liver cells.
    • Epinephrine and norepinephrine are collectively called catecholamines.
    • The body cannot sustain the bursts of energy mediated by epinephrine and norepinephrine for long times.
    • When an animal feels threatened, epinephrine and norepinephrine released by the adrenal medulla prepare the body to fight a threat or flee from it by breaking down stores of glycogen, which provides an immediate boost of energy.
  • Lipid-Derived, Amino Acid-Derived, and Peptide Hormones

    • For example, cortisol has a half-life of 60 to 90 minutes, whereas epinephrine, an amino acid derived-hormone, has a half-life of approximately one minute.
    • Examples of amino acid-derived hormones include epinephrine and norepinephrine, which are synthesized in the medulla of the adrenal glands, and thyroxine, which is produced by the thyroid gland.
    • (a) The hormone epinephrine, which triggers the fight-or-flight response, is derived from the amino acid tyrosine.
  • Humoral, Hormonal, and Neural Stimuli

    • Recall that in a short-term stress response, the hormones epinephrine and norepinephrine are important for providing the bursts of energy required for the body to respond.
    • Here, neuronal signaling from the sympathetic nervous system directly stimulates the adrenal medulla to release the hormones epinephrine and norepinephrine in response to stress.
  • Adrenal Glands

    • The adrenal medulla contains two types of secretory cells: one that produces epinephrine (adrenaline) and another that produces norepinephrine (noradrenaline).
    • Epinephrine is the primary adrenal medulla hormone, accounting for 75 to 80 percent of its secretions.
    • Epinephrine and norepinephrine increase heart rate, breathing rate, cardiac muscle contractions, blood pressure, and blood glucose levels.
    • The release of epinephrine and norepinephrine is stimulated by neural impulses from the sympathetic nervous system.
  • Adrenal Medulla

    • The adrenal medulla secretes approximately 20% norepinephrine and 80% epinephrine.
    • Cortisol also promotes epinephrine synthesis in the medulla.
    • Chromaffin cells of the adrenal medulla are innervated by the splanchnic nerve; they secrete adrenaline (epinephrine), noradrenaline (norepinephrine), enkephalin and enkephalin-containing peptides into the blood stream.
    • A pheochromocytoma or phaeochromocytoma (PCC) is a neuroendocrine tumor of the medulla of the adrenal glands (originating in the chromaffin cells), or extra-adrenal chromaffin tissue that failed to involute after birth and secretes high amounts of catecholamines—usually noradrenaline (norepinephrine) and, to a lesser extent, adrenaline (epinephrine).
  • Interactions of Hormones at Target Cells

    • For example, thyroid hormone increases the number of receptors available for epinephrine at the latter's target cell, thereby increasing epinephrine's effect at that cell.
    • Without the thyroid hormone, epinephrine would have only a weak effect.
  • Role of the Cardiovascular Center

    • Hormones such as epinephrine and norepinephrine or changes in pH such as an acidification due to carbon dioxide accumulation in a tissue during exercise are detected by chemoreceptors.
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