CogKnoSys

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Mental

Fight or Flight Response

The fight-or-flight response is the body's automatic reaction to a threat, preparing it to fight or run away.

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The idea

The fight-or-flight response is the body's automatic reaction to danger. It can be set off by an attack or any other threat to survival. It is also called the acute stress response or hyperarousal. Some animals freeze instead, so it is sometimes called fight-flight-or-freeze. The threat does not have to be real; what matters is that it seems harmful.

The response starts with a burst of activity in the sympathetic nervous system, which gets an animal ready to fight or run. The inner part of the adrenal glands, called the adrenal medulla, releases a wave of hormones. The main ones are norepinephrine and epinephrine, which is also known as adrenaline. These hormones make the heart beat faster, send more blood to the muscles and widen the pupils. Cortisol, estrogen, testosterone, dopamine and serotonin also affect how a body reacts to stress.

This reaction is the first stage of the general adaptation syndrome, a pattern of stress responses seen in vertebrates and other organisms. In a real emergency it can save a life. But the same reaction can switch on during everyday stress, such as before a test, when fighting or running away will not help. Once the threat passes, the parasympathetic nervous system helps the body calm down.

Check yourself

Question 1 of 3

Who first described the fight-or-flight response?

Pick one. The first pick counts.

Composition

what it's made of

  • Perceived threat — A harmful event, attack or danger to survival that sets off the response.
  • Sympathetic nervous system — Fires broadly to prepare the body to fight or flee.
  • Adrenal medulla — Releases catecholamines such as epinephrine and norepinephrine into the blood.
  • Other stress chemicals — Cortisol, dopamine, serotonin and others that also affect how the body reacts.
  • Freeze option — Some animals hold still instead of fighting or fleeing.

Connection

how it relates

Under Fear and Anxiety

Related

  1. Sympathetic Nervous Systemstrength 90 of 100

    A broad burst of sympathetic nervous system activity sets off the fight-or-flight response.

  2. Adrenaline Releasestrength 80 of 100

    Release of epinephrine, also called adrenaline, is a core part of the response.

  3. Parasympathetic Nervous Systemstrength 60 of 100

    The parasympathetic system works in the opposite direction, calming the body once the threat has passed.

Change

how and why it evolves

Past
Physiologist Walter Bradford Cannon first described the response in 1914. In 1915 he called it "the necessities of fighting or flight".
Now
Today scientists know that many hormones and brain chemicals shape the response, and some think the bone hormone osteocalcin may also play a part.
Next
A better understanding of the response may help doctors treat anxiety disorders and the effects of long-term stress.

Knowledge you can walk. Read the idea, then step up, across or down.

Fight or Flight Response

The fight-or-flight response is the body's automatic reaction to a threat, preparing it to fight or run away.

Learn, discuss, create, buy or invest

The idea

The fight-or-flight response is the body's automatic reaction to danger. It can be set off by an attack or any other threat to survival. It is also called the acute stress response or hyperarousal. Some animals freeze instead, so it is sometimes called fight-flight-or-freeze. The threat does not have to be real; what matters is that it seems harmful.

The response starts with a burst of activity in the sympathetic nervous system, which gets an animal ready to fight or run. The inner part of the adrenal glands, called the adrenal medulla, releases a wave of hormones. The main ones are norepinephrine and epinephrine, which is also known as adrenaline. These hormones make the heart beat faster, send more blood to the muscles and widen the pupils. Cortisol, estrogen, testosterone, dopamine and serotonin also affect how a body reacts to stress.

This reaction is the first stage of the general adaptation syndrome, a pattern of stress responses seen in vertebrates and other organisms. In a real emergency it can save a life. But the same reaction can switch on during everyday stress, such as before a test, when fighting or running away will not help. Once the threat passes, the parasympathetic nervous system helps the body calm down.

Check yourself

3 quick questions, instant feedback.