What is a Fight or Flight Reaction?

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  • Written By: wiseGEEK Writer
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  • Last Modified Date: 12 October 2019
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A fight or flight reaction is a response to stress characterized by boosts of adrenaline, dilated pupils and a fast heartbeat. The term was first used in the early 20th century by Walter Cannon, an American physiologist. Cannon used the term to describe animals that underwent situations where they either had to flee or prepare to fight in order to defend themselves from danger. Such a response can also be called hyperarousal, or a response to acute stress. According to Cannon’s descriptions, when an animal is frightened or imperiled, the sympathetic nervous system responds, causing adrenaline boosts and changes in pupils and heartbeat, and sometimes extra strength shown in bursts of speed if an animal runs away or stays to attack. Some also refer to a third state “fright,” occurs when an animal doesn’t flee or fight, but panics and passes out or stands still — the typical “deer in the headlights” response or the collapse of sheep if chased by a dog.

Fight or flight reaction has also been found to occur in humans during times of stress or danger. In some cases, the sympathetic nervous system causes such extreme boosts of adrenaline that people are able to do things they couldn’t under ordinary circumstances, like lift a car off an injured loved one. The fight or flight response can be extremely powerful, but it doesn’t always work to our advantage.


People may encounter this reaction not just in situations of perceived physical danger. They may also feel imperiled during a vocal argument. This can cause them to continue arguing, and some people may even combine physical attack if their sympathetic nervous system works overtime during any type of verbal attack. Others need to flee, and if a person really wants to get out of a verbal argument, you shouldn’t try to stop him or her, since flight can be provoked into fight, if a person can’t get away from the attack and feels cornered.

Moreover, some people, especially those with post traumatic stress disorder (PTSD), panic disorder or generalized anxiety disorder, may have a fight or flight reaction for no apparent or obvious reason. The sympathetic nervous system essentially misfires, and suddenly being unable to find your keys, or something else mundane, causes a rapidly beating heart, heavy breathing, or an outright panic attack. For people with PTSD, small reminders of past traumatic events, like a smell, the temperature or being in a place familiar to where traumatic events occurred can provoke this response. For some, this can provoke aggressive behavior toward others, and yet others find themselves panicking or needing to change environments quickly.

Sometimes the flight response is not particularly overt in humans. Withdrawing from social interaction, even by watching television or surfing the net, could be viewed as a slight flight reaction when times get stressful. In studies on gender and fight or flight reaction it has been observed that men tend to become more aggressive or more withdrawn than do women under stressful situations, probably because in our culture, women tend to be more likely to lean on social resources (friends and family) to discuss their problems.

In all, most people will encounter fight or flight reaction in times of stress. Though it may have once been an instinctual behavior to protect people from danger, just as it now protects many animals, it is sometimes a hassle to deal with. Being in a full hyperarousal state can lead to bowel problems, panic, argumentative mood, withdrawal, and difficulty sleeping and breathing. If this response seems to occur frequently without stimuli, like a real danger or stressful situation unfolding, it may be wise to evaluate ways to address this response with a mental health professional or with your personal physician.


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Post 6

I got here following a google search to try to understand what happened to my sheep.

This morning I heard a loud noise coming from my yard but saw nothing special. When I went to feed the animals, I noticed that only one of my two sheep came to eat, which isn't normal, so I want to look for the other one. I heard some moaning coming from one of the barns and rushed over to find her lying down and struggling to get loose from a piece of fence where she got her back paws stuck.

She was obviously exhausted and very stressed from all that exertion and I wonder how long she had been there. With a lot

of difficulty, I managed to got her loose and tried to help her up but she wasn't able to stand. So I helped her find a more comfortable position to calm down.

After a few minutes she seemed calmer, but she was breathing very heavily and her eyes were wide open. It seemed like she couldn't even see because she wouldn't react when I swung my hands side to side right in front of each eye.

After reading this text, I realized that what I had corresponds with what happened and trust that she will recover her energy in due time.

Thank you for this very useful information!

Post 5

I've heard of people doing crazy things like lifting cars before. I never really thought it was possible, but I guess I was wrong. I can't believe that our bodies are designed to do such impossible things if the situation calls for it.

I hope that if it came to a situation like that, I would be able to stay and fight.

Post 4

I definitely have a tendency toward flight. I hate confrontations, and I even tend to leave the room when other people get into a debate -- even a friendly one. It just makes me uncomfortable. I know people who thrive on debating with others. I'm guessing those would be the people to stay and fight during a time of extreme stress.

When it comes to fight or flight in an anxiety filled situation, I'm gone. I realize that this may not be the healthiest way to deal with problems. Maybe, if I consciously work on it, I can change this tendency, until I'm more at a balance between the two.

I don't want to stick around when it's unsafe to do so, but I don't want to flee when I should be sticking up for myself. There has to be a good middle ground that I can reach.

Post 3

I have sometimes been seen as aloof because I tend to withdraw from situations at unexpected moments. This often leaves people wondering what they said, and if I had had a fight or flight reaction to them. Usually, this is not the case, but I have a personality which is seen by some as aloof. It is so difficult for me to explain to them that this is just the way I am.

Post 2

When my husband was a teenager, he exhibited a fight response when flight would have been the safer way to go.

He had the horrible experience of being carjacked, at gun point. When the attacker told him to get out of the car, he responded by telling him no, and arguing with him.

Thankfully, he eventually got out, before he was hurt. But when I heard this I couldn't believe it. I asked him why he didn't just get out of the car immediately -- it was old, and beat up, and not worth much anyway. He didn't really have an answer, but it just goes to show that when it comes to fight or flight reactions, you can't predict what you would do in a dangerous or stressful situation.

Post 1

Can you post a biography about Walter Cannon?

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