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Picture yourself cranking out a heavy set of squats, your training partner counting down as rep number 20 of an ultra-brutal series approaches. The final rep has arrived and you can hardly bring it to completion. Lungs burning, breathless, and with fully-pumped quad muscles screaming for mercy, you are ready to rack the weight. However, your partner has other ideas and, with no warning given, demands 10 more reps. Unable to think clearly, stomach churning with nausea, you must make an important decision: continue or quit, fight or flight. Knowing that winners never quit, you mentally commit to achieving the seemingly impossible. A remarkable series of complex biochemical processes are on standby, ready to assist you in such an event.  Before you can properly rationalize all the implications of your decision to continue, the amygdala of the brain engages a neural response causing the pituitary gland to release the hormone ACTH (Adrenocorticotropic hormone), which immediately tells the adrenal glands to produce the hormone cortisol.[2] Your blood sugar, heart rate, and blood pressure all skyrocket.[4] Immune system activity ceases (the body has more immediate concerns and must mobilize only that which is necessary to complete its mission). Fatty acids align with glucose to boost energy levels. And finally, the catecholamines, including norepinephrine, are called upon to facilitate immediate physical reactions to complete a task that would be out of the question under less harrowing circumstances. What happens next is largely directed by how well prepared you are for violent muscular contraction. With 300lbs pressing down on your spine and nothing left in the tank you have no choice but to lift, or lose.

The nature and intensity of your behavioral response and the planning of how best to approach such a mammoth effort, both prompted by norepinephrine release, will, it is hoped, guide you to the completion of all ten additional reps. Fully prepared, your breathing and lung function increases to deliver more oxygen to the body and brain; metabolic processes such as digestion and growth are halted so the blood that is normally used  for these actions can be directed to the muscles and brain; blood vessels leading to muscles are dilated so more fuel and oxygen can be delivered; and muscle tension is increased to provide the body with extra strength and speed. With the aid of norepinephrine, you successfully mobilize the energy and aggression needed to max out at 30 reps – the ‘emergency’ has passed. Because of the enormously taxing nature of this event, the body cannot sustain such an intense onslaught for very long. Your breathing is calmed, your nerves are no longer on edge, your senses are no longer heightened, hunger, thirst, elimination and other bodily functions are returned to normal. Until the next set, it is all systems go.

The Science            

The chemical primarily responsible for helping us to focus and (along with epinephrine) initiate the fight-or-flight response is norepinephrine – a.k.a. noradrenaline. Adopting many roles, as a neurotransmitter, norepinephrine affects multiple areas of the brain, in particular the amygdala, an almond-shaped group of nuclei situated deep within the temporal lobes. Here, norepinephrine directs attention and helps to control our responses to external environmental stimuli. [7][2][9]

As a neurotransmitter released from the postganglionic sympathetic neurons of the peripheral nervous system, norepinephrine stimulates cardiovascular function and increases blood flow to working muscles. It also initiates the release of glucose from energy stores, and provides more oxygen to the brain. Critical for the functioning of the heart, elevated norepinephrine causes an increase in heart rate to prepare the body for increased physical activity. [4][1][6]

As outlined earlier, norepinephrine enables us to do the seemingly impossible; to intently focus on completing tasks which demand our combined energy resources and immediate action. By enhancing respiration, increasing muscle activity, boosting heart rate, and intensifying muscle contraction, norepinephrine transforms the way we respond to a acute stressor. Because norepinephrine mobilizes fat molecules to generate additional energy, it allows the body to burn fat more efficiently as well [8, 10].

Maintaining Balance

Norepinephrine is a neurotransmitter and hormone that must remain in proper balance with other chemicals of the catecholamine family to ensure our biological systems function as they should, when they should. Too much norepinephrine and we may become anxious, irritable, and aggressive, and our muscles may remain constantly tensed and prepared for action; all of which may combine to deplete our energy reserves. On the other hand, low levels of norepinephrine may cause poor cognition, depression, and a loss of alertness. In most circumstances our bodies are experts at orchestrating the exact amount of norepinephrine we need, but if your levels are problematically low the following steps can be taken.

• Exercise: known as an aid to virtually all that ails us, exercise also improves norepinephrine function. [3]

• Diet: all proteinaceous foods containing the amino acid tyrosine are great for norepinephrine production: lean beef, chicken, turkey, eggs, cold-water fish, and pork are particularly good sources. Other tyrosine-rich foods include avocados, pumpkin seeds, dairy products, almonds and bananas. Several (4-5) protein dense meals per day with whole grains and vegetables will boost norepinephrine and optimize health, wellbeing and muscle gains. The amino acids L-phenylalanine and L-tyrosine along with vitamins B6, B3, folic acid, vitamin C, and minerals iron and copper are also known to boost norepinephrine levels. [3]

In Conclusion

Whenever we are forced to confront an unexpected obstacle, to swing into action at a moment’s notice, we react by increasing our brain activity. When it comes to processing information and charting a course of action, we have norepinephrine to thank for giving us the ability to mentally conceive and physically respond in an expedient manner. Furthermore, norepinephrine transcends the boundaries of the central nervous system to initiate the cascade of physiological effects that allow us to push past seemingly insurmountable obstacles. Norepinephrine is a formidable weapon in our fight for growth, and it is not to be trifled with.

References

1. Cardiovascular Physiology Concepts. Circulating Catecholamines. [Online] http://cvphysiology.com/Blood%20Pressure/BP018.htm retrieved on 30.1.15
2. Bennington, V. Understanding our Adrenal system: norepinephrine. Breaking Muscle.  [Online]http://breakingmuscle.com/health-medicine/understanding-our-adrenal-system-norepinephrine retrieved on 30.1.15
3. Dorman, K. Natural Ways to Raise Norepinephrine. Livestrong. [Online] http://www.livestrong.com/article/199980-natural-ways-to-raise-norepinephrine/ retrieved on 301.15
4. Guyton, A.,  Hall, J. (2006). Chapter 10: Rhythmical Excitation of the Heart”. In Gruliow, Rebecca. Textbook of Medical Physiology (Book) (11th ed.). Philadelphia, Pennsylvania: Elsevier Inc. p. 122.
5. Klabunde, R. Norepinephrine, Epinephrine and Acetylcholine – Synthesis, Storage, Release and MetabolismCardiovascular. Pharmacology Concepts. [Online] http://www.cvpharmacology.com/norepinephrine.htm retrieved on 30.1.15
6. Rinaman, L. Hindbrain noradrenergic A2 neurons: diverse roles in autonomic, endocrine, cognitive, and behavioral functions. Am. J. Physiol. Regul. Integr. Comp. Physiol. 300, R222–R235 (2011).
7. Robertson, S., Plummer, N., de Marchena, J., & Jensen, P.  Nature Neuroscience 16, 1016–1023 (2013)
8. Schuster, S. Norepinephrine Versus Epinephrine. Livestrong. [Online] http://www.livestrong.com/article/226152-norepinephrine-vs-epinephrine/ retrieved on 30.1.15