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Difference Between Epinephrine and Norepinephrine

epinophrineEpinephrine vs Norepinephrine

Both Epinephrine and Norepinephrine are similar chemical messengers released by adrenal medulla. Both of these messengers belong to the chemical class of catecholamine, which are derived from an amino acid called tyrosine. These adrenomedullary hormones play essential role in stress responses, arterial blood pressure, and fuel metabolism.

In terms of their structure, Epinephrine and Norepinephrine are the same except that epinephrine has a methyl group. Both Epinephrine and Norepinephrine are synthesized within adrenomedullary secretory cells and both are stored in Chromaffin Granules.

In terms of total adrenomedullary catecholamine output, epinephrine takes for 80% and Norepinephrine for 20%. When it comes to the production of these catecholamine molecules, epinephrine is produced exclusively by the adrenal medulla, whereas the large amount of Norepinephrine is produced by sympathetic postganglionic fibers. Therefore, the effects of Norepinephrine are largely mediated by the sympathetic nervous system and the effects of epinephrine are brought about exclusively by the adrenal medulla.

Both Epinephrine and Norepinephrine vary in their affinities for adrenergic receptor types such as alpha 1, alpha 2, Beta 1 and Beta 2. Norepinephrine binds primarily with alpha and beta 1 receptors located near postganglionic sympathetic-fiber terminals. Epinephrine interacts with the same receptors as of Norepinephrine, but epinephrine has greater affinity to alpha receptors compared to Norepinephrine. Both hormones have the same potency towards beta 1 receptors. That is why both epinephrine and Norepinephrine show same effects in many tissues.

Epinephrine can also act on beta 2 receptors through the blood stream. Epinephrine can bring about metabolic effects by breaking down stored glycogen and causing broncho-dilation on bronchiolar smooth muscles. It can produce vasodilation of the blood vessels that supply to skeletal muscles and to the heart through Beta 2 receptor activation. The other most important action of epinephrine is that it constitutes a fight-or-flight response that prepares the person to fight an enemy or flee from danger. Epinephrine also increase the cardiac output by increasing the rate and the strength of cardiac contraction. The epinephrine’s general vasoconstrictor effect increases the arterial blood pressure and therefore epinephrine come into play during cardiac arrest as a cardiac drug. Only epinephrine dilates the respiratory airways to reduce the resistance of moving air in and out of the lung. Both Epinephrine and Norepinephrine reduce digestive activity and prevent bladder emptying.

1.Both Epinephrine and Norepinephrine belong to the same chemical class called catecholamine and they are very similar chemical messengers released by adrenal medulla.
2.Both play a major role in stress responses, arterial blood pressure, and fuel metabolism.
3.Both Epinephrine and Norepinephrine vary in their affinities for adrenergic receptor types such as alpha 1, alpha 2, Beta 1 and Beta 2.
4.Both Epinephrine and Norepinephrine show same effects in many tissues.
5.Both Epinephrine and Norepinephrine reduce digestive activity and prevent bladder emptying.

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  1. Apart from “Epinephrine is a derivative of norepinephrine” this is just wrong, or at least silly. What i assume is supposed to be “Norepinephrine converts glycogen to glucose while [epinepherine] increases the catabolism of glycogen” isn’t a difference. converting glycogen to glucose is the same as catabolism of gylcogen. Is it not?

    • Norepinephrine and epinephrine differ in their effects on blood vessels.Norepinephrine causes vasoconstriction of all blood vessels whereas epinephrine causes vasoconstriction of blood vessels supplying the skin and gut and vasolidation of blood vessels to muscles and the brain.

  2. So much of this article is incorrect! Norepinephrine definitely does NOT calm the system down. These are both neurohormones of the sympathetic nervous system–aka the “fight or flight” system. Epinephrine, not NE, increases blood glucose by breaking down glycogen. This is a very poor article.

  3. I never read anything about norepinephrine being a hormone/neurotransmitter that calms the system down.

  4. Epinephrine (/adrenaline) supplied by the Renal medulla does however relax Beta 2 adrenergic receptors in the airway causing bronchodilation – increasing the size of the airway lumen and making it easier to breath. Another example of a Beta 2 agonist which performs a very similar task is Salbutamol, which you will find in a blue inhaler (usually a 100mg dose). I imagine this greatly calms down the sufferer of an asthma attack.

  5. Reply to Ian’s answer:
    NE also breaks down glucose from glycogen when in need.
    Ref: http://en.wikipedia.org/wiki/Norepinephrine

  6. epi and nor-epi (aka, adrenaline and noradrenaline respectively) both are catecholamines. they both have similar chemical structure and function with few differences…they are both sympathomimetic (responsible for fight or flight response) which is somewhat opposite to parasympathetic action..nor epinephrine is released from all sympathetic effector organ nerve terminals and acts mostly at the vicinity so its a neurotransmitter….epinephrine is secreted by adrenal medulla( which is homologous to sympathetic neuron cells) and is circulated via blood and acts on target tissue/organ away from where it is released; so it is a hormone…..nor-epinephrine works on alpha 1, alpha 2, and beta 1 receptors……but epinephrine works on all alpha 1, alpha 2, beta 1 and beta 2 receptors…….by working on beta 2 receptors which are found on lungs’ airway smooth muscle and in skeletal muscle’s blood vessels, epinephrine dilates those air tubes and skeletal muscle’s blood vessels which is crucial in fight or flight response or during exercise….

  7. Epi and Norepi are both stimulants therefore neither calms anything down . Just use local anes in surg Xylocaine with epi and see what happens to the heart rate .

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