Epinephrine

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Transcript

            Did you know that adrenaline has another name, and that it’s actually used more often?  This hormone currently goes by the name epinephrine, and it has a key function in our bodies.  Have you ever heard of fight or flight, the impulse to either run or stand your ground in a dangerous circumstance?  How about a person lifting a car off of their child in a life or death situation?  Well these responses are caused by epinephrine, which is released when the brain experiences stress.  When it is released into the blood stream, it can raise your heart rate, strength, blood pressure, and metabolism to make you a more highly functioning human being.   However, its effects are only temporary so epinephrine can’t make us all Superman.

             Epinephrine is produced in the medulla, or core, of the adrenal gland, which sits on top of the kidneys.  When you feel stressed, angry, or afraid, your brain releases a signal through the sympathetic nervous system to the adrenal gland, which begins to produce epinephrine.  Since this process begins with a response in the hypothalamus that triggers another response in the adrenal gland to produce the hormone, it is a neuroendocrine pathway. 

When epinephrine is released, it binds to the outside of cells, called adrenergic receptors, on their membranes.  There are two types of adrenergic receptors, alpha and beta, that have different responses when the epinephrine binds to their membranes.  This bond makes the receptor change its shape to become active.  From this point on, the epinephrine functions through a series of G proteins that produce GDP.  The proteins activate an enzyme that converts mass amounts of ATP into signaling molecules.  After a certain amount of time, the receptors become inactive, but the chemical reaction continues, eventually removing phosphate groups from glucose molecules.  Without the phosphates, glucose can directly pass into blood cells, creating the fight or flight response.     

Epinephrine has two types of feedback loop: the adrenaline-cardiovascular feedback loop and a short-term stress response.  The adrenaline-cardiovascular feedback loop is dependent on your heart rate.  When your heart rate is too slow you produce epinephrine to make it faster, but if it is too fast epinephrine production stops.  The short-term response is caused by either perceived or threatening stress.  With perceived stress, or the stress caused by your job or homework, the epinephrine is underused and can be harmful.  With threatening stress, or that car speeding toward you, your body releases epinephrine in order for you to have the best chance of staying alive.  In all situations, your hypothalamus sends signals through your spinal cord telling your adrenal glands that you need the epinephrine to survive.  This entire system is a negative feedback loop, as the production of epinephrine does not provide for more of the hormone to be made, but new studies are showing that extreme circumstances can make its production into a positive feedback loop.

The last, but not least, important fact about epinephrine is that it is hydrophilic, allowing it to diffuse through blood plasma and dissolve in water.  This is evidenced by its bonds with the cell membrane, as opposed to the nucleus of cells, since the membrane is made of some fats.  Water-soluble hormones are made of amino acids, the building blocks of proteins.

While all these scientific facts about epinephrine make it sound strange, everyone has heard of an epi pen.  When someone with an allergy goes into anaphylactic shock, epinephrine is used to get their heart going and change their blood flow so that swelling will decrease.  Epinephrine is a large part of modern medicine and culture, with phrases like “adrenaline junkie” used commonly today.  This hormone is one of the most well known and important in our bodies, even if we only know it by a different name.      

References

"Signal Transduction Pathway." Whfreeman.com. W H Freeman Publishers, n.d. Web.

Cashin-Garbutt, April. "What Is Epinephrine (Adrenaline)?" News-medical.net. News Medical, n.d. Web. 

"Epinephrine Molecule." Worldofmolecules.com. World of Molecules, n.d. Web.

"Epinephrine." Udel.edu. University of Delaware, n.d. Web.