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Fight or Flight? What it is and Why We Need it

The Author

Hello, my name is Maddy Schoop and I am a Junior biology major at Mount Aloysius College. I took an interest in the stress response because as I was learning about it in several psychology and anatomy classes throughout the years, I often thought about where this reaction originated, and why it did. I am also interested in how the chemicals released from the stress response affect the body and how they are an advantage in a dire situation but a disadvantage when the threat is missing.

What is the Fight or Flight Response?

You’re in your car driving to work and suddenly another car coming from the street to the left runs a stop sign and you feel your heart drop as you hit your brakes quickly to avoid a collision. After avoiding the accident, you catch your breath and feel the adrenaline that has just spiked inside your body. Your heart is pounding but you feel it start to slow. We’ve all been in this situation, I know I’ve been in it more than once, and it is a common modern-day experience of the stress response, commonly referred to as the Fight or Flight Response. The stress response, also known as the fight-or-flight response, can be triggered by anything that the brain perceives as a threat, in the example above the car that had run the stop sign was the threat and your body responded quickly in a way to protect you. The stress response developed a long time ago and has adapted over the centuries.

The Origin

Many centuries ago, the level of danger in the surrounding area was typically pretty high, considering cavemen did not have abundant shelter or weaponry to protect themselves. With so many potential predators around, humans had to develop a way to react quickly in order to prevent possible death. They needed a way to quickly evaluate a situation and formulate a reaction that would prevent harm. Imagine living in a world where instead of going to the grocery store, you had to hunt for all of your food and encounter predators on a daily basis. When the cavemen encountered a predator they had to make a quick decision, do I run or do I fight? Throughout time and many exposures to danger, the human brain initiated a chemical reaction to maintain homeostasis under pressure and quickly react to threats, this reaction has evolved through time to become the stress response we know today.

How it Works

The stress response all begins with the sympathetic nervous system (SNS). So for simplicity, let’s go back to that little traffic issue from the beginning, when you saw the car run the stop sign your brain immediately recognized it as a threat. An area in your brain, the amygdala, sent a distress signal to the hypothalamus causing cortisol to be released and the SNS to be triggered. Then one of the first hormones to be released from the adrenal glands is epinephrine (commonly known as adrenaline). Epinephrine causes a multitude of changes throughout the body to increase alertness. The body’s airways expand to breathe in as much air as possible, breath rate increases, the heart starts to pump faster allowing for more blood circulation to the brain and other parts of the body, and the pupils dilate. Think of it as your body working at 100% efficiency. This instant reaction is what coined the term “fight or flight response” and many people often describe it as an “adrenal rush” which is actually a large part of it. This entire process takes place within seconds and allowed you to make the quick decision to brake in order to avoid colliding with the other car.

So you may be wondering why you felt the adrenaline die down in your body after the incident. That would be the beginning effects of the Parasympathetic Nervous System (PNS) which is also referred to as the “rest and digest” system. The PNS acts to relax your body and return to homeostasis after the stress response was triggered. The PNS reduces cortisol levels, shrinks the pupils from the dilated state, and slows the heart down to a normal resting rate. It can take 20 to 30 minutes to return to homeostasis. Returning to homeostasis is just as important in the stress response as the initiation. Without returning to a healthy resting state, the body can experience negative effects.

Overdoing It

The stress response is a wonderful life-saving reaction but when it is consistently triggered in the absence of a true threat, it can do damage to the mind and body. Long-term perception of stress can leave your body in a prolonged state of the stress response which interferes with many bodily functions. Overexposure to cortisol, causes your body to be in a chronic state of stress. Cortisol is useful in releasing glucose into the bloodstream during the stress response and it suppresses nonessential bodily functions, like digestion, during the response. However, when your body is consistently exposed to cortisol, digestive functions are turned off or not functioning as they should. This could lead to digestive issues and pain as well as weight gain. Overexposure to adrenaline can cause mental health issues such as anxiety and depression and it also can cause high blood pressure and other heart conditions. So while the stress response can save a life, a constant state of it can make life much harder.

Conclusion

The stress response was a necessity in early human civilization and it has evolved over centuries to continue to protect the human species. It pumps chemicals throughout the body to make it work optimally in a life or death situation. The PNS comes in after the stress response is initiated to return the body to normal. When the body is in a chronic state of the stress response physical and mental health can deteriorate. It is essential to life as a human when kept in homeostatic balance. With this information in mind, take a minute to relax and thank your brain for keeping you safe in the face of danger. Also, check out the infographic that I made below for a visual representation of the stress response!



References

Nesse Evolstress response - university of michigan. (2007). Retrieved from

http://wwwpersonal.umich.edu/~nesse/Articles/Nesse-EvolStressResponse-2007.PDF Understanding the stress response. Harvard Health. (2020, July 6). Retrieved from

https://www.health.harvard.edu/staying-healthy/understanding-the-stress-response Harkness, K. L., & Hayden, E. P. (2020). The Oxford Handbook of Stress and Mental Health.

Oxford University Press. 1



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