Difference Between Epinephrine and Norepinephrine
Epinephrine 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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