Epinephrine vs Norepinephrine
Epinephrine (adrenaline) and norepiphrine (noradrenalin) are known as neurotransmitters that belong to a chemical class of catecholamines; which are derived from thyrosin. Both these chemicals regulate attention, mental focus, arousal, and cognition in humans. These neurotransmitters have approximately the same potency for all the receptor types; α and β. Thus, their effect in all the tissues is somewhat similar, though they are different in their chemical structure.
Epinephrine (also known as adrenaline) is released by the adrenaline glands and is responsible for the regulation of body’s “fight or flight” response. It regulates the transfer of nerve signals between neurons and the body cells and increases the rate and strength of cardiac contraction. Epinephrine is usually released when the person is in stress or excitement. Unlike the norepinephrine, the effect of epinephrine is unpredictable, due to the differential sensitivity of receptors. However, it has approximately the same affinity for all the receptors including α1, α2, and β1 with the exception of β2. Adrenaline medulla is responsible for the production of epinephrine and mediates the action of epinephrine. However, the epinephrine secretion is indirectly controlled by the sympathetic nervous system.
Norepinephrine is an excitatory transmitter located in the sympathetic nerves of the peripheral and central nervous system. It is more similar to epinephrine and is secreted by the adrenal glands during the stress or arousal conditions. Norepinephrine increases the heart rate by firing of the SA node. It also affects calcium flux within cardiac muscles resulting in a positive dromotropic and inotropic effect.
Norepinephrine is used as a drug in the treatment of septic shock, in adults. Norepinephrine functions in two major tracts in the body. First it influences the behaviors by connecting the brainstem with axons in the hypothalamus and limbic system. Second, it affects the nerve tract extends from the brain stem to the cerebral cortex and hippocampus. Norepinephrine in the spinal tracts regulates the anxiety and tension.
What is the difference between Epinephrine and Norepinephrine?
• Epinephrine has a methyl group attached to its nitrogen, whereas norepinephrine has a hydrogen atom in place of the methyl group.
• Norepinephrine is produced by sympathetic postganglionic fibers while epinephrine is produced only by the adrenal medulla.
• The effects of norepinephrine are largely mediated by the sympathetic nervous system, whereas that of epinephrine is mediated only by the adrenal medulla.
• Epinephrine is responsible for controlling all the body tissues, whereas norepinephrine regulates the parts of the brain, which are responsible for the mind-body relationship and responding actions.
• Norepinephrine has a little greater affinity to bind with α-receptors than epinephrine.
• The effect of norepinephrine is more predictable, unlike the epinephrine due to different sensitivities for α and β receptors.