Fight or Flight Response: What It Is & How It Works

What Is the Fight or Flight Response?

The fight, flight, or freeze response is often used to describe our reaction to something imminent and scary. In the above example, you do not know what is approaching from behind, and your body tenses as it braces for impact. You freeze, not moving a muscle. The fight or flight response is instinctual to something physically or mentally scary.

The fight or flight response is a natural response to a stressful situation, and it evolved as a survival mechanism. We are instinctually driven to engage in this response to protect ourselves, as it “prepares the body to handle the challenges presented by an internal or external environmental challenge.”¹

The three stages of the fight or flight response are:

1. Alarm: This is the initial response when we detect a threat. When our pupils dilate, our back straightens, and our body prepares to fight or flee.
2. Resistance: This is when the body attempts to recover and normalize its processes following the threat. Think of the sigh you make or the relaxing of your back and shoulders after you realize that the car barreling towards you slowed down.
3. Exhaustion: When we realize that the danger has passed and that we are safe, it is common to feel a sense of calm or even exhaustion. This is the adrenaline leaving our body and allowing us to return to equilibrium. “After the perceived threat disappears, the body returns to pre-arousal levels.”¹

Fight or Flight Response Examples

The fight or flight response is usually triggered by an imminent threat. A dangerous animal or person approaching us, a car barreling towards us as we cross the street, or another potentially dangerous event that forces us to activate a biological response to survive.

What Happens in the Body During the Fight or Flight Response?

During fight-or-flight, our sympathetic nervous system takes over. It increases our heart rate, which increases blood flow and circulation to prepare us for movement. Our bladder relaxes, pupils dilate, and our lungs increase airflow.² This is all to prepare us to survive a threat.

Our autonomic nervous system is the part of our body that controls our automatic drive to live. These are things such as blinking, breathing, and digesting- all things we do not think about as long as they work as they should. The autonomic nervous system consists of a sympathetic nervous system and a parasympathetic nervous system, both of which control biological drives and processes.

Physical effects of the fight or flight response include: 

• Circulation: During fight-or-flight, our body increases blood flow to muscle groups needed for movement and decreases blood flow to muscles not needed for movement. This begins the process of preparing the body to fight or flee.¹
• Eyes: Our pupils dilate, which allows increased focus and visual perception of incoming threats.
• Heart: The fight or flight response increases the heart rate, which increases circulation throughout the body to prepare areas of the body needed for movement.
• Liver: Our liver experiences increased availability of glucose to give the body energy to fight or flee a dangerous situation.
• Lungs: Our lungs expand and allow for increased airflow, which helps with circulation.
• Skin: Our skin flushes due to decreased blood flow to nonessential body parts.

Fight or Flight Hormones

The fight or flight response involves hormones throughout our body to facilitate whether we fight or flee a potentially dangerous situation. The brain sends a distress signal when it senses a threat, which activates our sympathetic nervous system. This sends signals to the adrenal- or hormone- glands that start pumping adrenaline into our bloodstream to prepare us with energy to fight or flee.

If the brain continues to sense an imminent threat, our adrenal glands are prompted to release cortisol, keeping the body amped up and prepared to fend off an attacker or flee a dangerous situation. “When the threat passes, cortisol levels fall. The parasympathetic nervous system — the “brake” — then dampens the stress response.”³

Evolution of the Fight or Flight Response

Like all of our biological responses, the fight or flight response developed due to the conditions experienced by our ancestors, who had to adapt and react to threats safely to survive. The quicker they could respond physically and psychologically, the greater their chance of survival.

Even though we are no longer threatened by mammoths and saber tooth tigers, we still have the instinct to protect ourselves to survive. Our drive has evolved to respond to different but still equally threatening things, such as attacks and dangers in our environment.

Why Is the Fight or Flight Response Important?

The fight or flight response is important because it protects us from a potentially life-threatening situation. However, it can also be beneficial even in non-life-threatening events. Giving us the push we need to succeed under pressure at work or during a legal battle are some examples of how this drive helps us.

How Can the Fight or Flight Response Be Harmful?

The fight or flight system is a normal response and is usually no cause for concern. However, if it happens to you even during non-life-threatening events, this can harm your physical and mental health. People who have experienced high levels of trauma or dysfunction will experience more frequent surges of cortisol- also known as the stress hormone. In small doses, this hormone is fine. However, increased amounts of cortisol and adrenaline can damage the body over time.⁴

Having an overactive fight or flight response is common for people who have experienced childhood trauma and those with anxiety disorders, phobias, PTSD, and panic disorder.

How to Calm Down After the Fight or Flight Response

While the fight or flight response can be beneficial, it has drawbacks. If we stay in an activated state for too long, it can negatively impact our physical and mental health. Therefore, learning to calm your body down when experiencing an overactive response is important.

Here are eight ways to calm the body after the fight or flight response:

1. Take three deep breaths: Breathing is a natural way for our body to calm itself. Take three deep breaths to begin the process of returning to a state of pre-arousal.
2. Grounding techniques: Using grounding techniques is a helpful way to distract or soothe during distress.The 333 rule and 54321 method are great tools for times of stress to help ground you.
3. Take in your surroundings: When we are in fight or flight, it is easy to lose focus of what is happening around us. Notice the trees, their colors, and textures, to help orient you back to the present moment.
4. Remind yourself that you are safe: Take a moment to remind yourself that you are safe. Saying things such as “the car has passed,” or “the dog wasn’t able to get me” will help.
5. Increase understanding of biological responses: When we learn more about why our body behaves in certain ways, it is easier to understand why we feel the way we do during a threatening event. Remind yourself that it is normal and that there are actually benefits to our fight or flight response, as long as it happens when it should. These benefits include an increased ability to respond to danger and escape a threatening situation. Reminding yourself that this response is normal can help.
6. Call a friend or support person: Conversing with a loved one can help calm you just by hearing their voice. It will also help if you are the type of person who feels calmer after processing the stressful situation with someone else.
7. Engage in regular stress management: It is easier to return to baseline if we are used to calm ourselves. Those who stay in a heightened stress response are usually those who struggle to get their stress levels under control. Make sure to get regular sleep and exercise, and see your medical doctors when needed.
8. Physical Activity: When our body has adrenaline soaring through it after a fight or flight response, sometimes we need a place for that energy to go. Do 10 jumping jacks in your home or office, or briefly walk around the block if you can. This will help redirect the energy and help it leave the body in a healthy way.

When to Seek Professional Support

In most instances, our fight-or-flight response is a natural drive and nothing to worry about. However, for those who experienced trauma, their fight-or-flight response might be exaggerated. This can be stressful to experience a startle reflex during events that do not bother other people while we sit there with a racing heart and tense shoulders.

When this happens, it might be beneficial to seek therapy to combat the trauma and decrease the startle response to make life more manageable. You can use an online therapist directory or online therapy platform to find a therapist specializing in trauma and anxiety, or ask your friends or primary care doctor for a referral. In some cases, medication management might be needed to decrease symptoms of anxiety and tension. Online psychiatrist options are available for those who need them.

In My Experience

As a therapist specializing in working with survivors of chronic childhood family trauma, I find that many of my clients, myself included, have an exaggerated startle fight-or-flight response. This is due to the many years of needing to brace ourselves for what was coming next, which was often unpredictable. Over time, our body becomes conditioned to immediately go into this fight-or-flight defense mechanism, even when it isn’t needed. A situation such as someone dropping a heavy book can make survivors startle and gasp while others in the room barely notice it. This is when a biological response becomes exacerbated by a trauma response.