Fight, flight, freeze response: how your body reacts to stress.

Trigger warning – themes of survival and death.

Have you ever wondered when you’re nervous or in a pressured situation your hands get sweaty, you shake, your stomach churns and your heart rate increases?

You might have noticed other responses, like your voice going quiet or being unable to speak, suddenly needing the toilet or surrounding sounds seeming louder than usual?

This is the body’s natural reaction to perceived danger – it’s known as the fight, flight, freeze response.

Fight, flight, freeze –

This is an automatic instinctive response to danger, and it’s been keeping humans alive for thousands of years.

The biggest threat to our ancestors were the fierce conditions they lived in such as competing tribes and predators. Fast forward to today, we don’t have these types of threats of immediate danger and our lives are very different. It can be strange and uncomfortable to experience this in the modern-day world. However, it still serves a strong purpose… survival.

When faced with a tiger in the wild, our instincts take over and our body almost immediately assesses whether we’re going to fight the tiger, run away or freeze and wait to be eaten.

The emotional and sensory part of the brain, the amygdala, is much faster than our rational thinking part of the brain, the prefrontal cortex, which partially shuts down in the fight, flight freeze response.

The biological process –

Here’s a very basic sequence of main events that cause the fight, flight, freeze response in the body:

  • Your body senses the threat, and the sensory information is relayed to the brain.
  • Part of the limbic system in the brain, the amygdala, is activated which sends a signal to the hypothalamus.
  • The hypothalamus, which regulates the hormones in the body, sends signals to the adrenal gland.
  • The adrenal glands releases adrenalin, noradrenalin and cortisol (stress hormones) into the blood stream.
  • The stress hormones interact with organs in the body to prepare for fight or flight.

This is known as sympathetic nervous system activity and it results in the following changes:

  • Increased heart rate (to increase blood flow to the major muscle groups to prepare for action).
  • Increased breathing rate (to increase oxygen available in the blood for the muscles as fuel for potential action).
  • Pupil dilation (to enhance vision to keep up to date with the movements of the threat).
  • Sweat production (to regulate temperature because of potential action).
  • Reduction of non-essential body function (to decrease activity in the digestive system and immune system).

A note on freeze –

As a last resort, if the threat is 100% unavoidable the body will go into shut down mode as it prepares for injury or death by reducing the perception of pain. This can cause dissociation or an outer body experience and numbness.

The fight, flight, freeze response is helpful when faced with a tiger. However, it becomes problematic when we need our thinking part of the brain like when are about to deliver a presentation or even speak with a person under stressful situations. Moreover, the fight, flight and freeze response is physiologically taxing and exhausting on the body since it is only to be used as a temporary emergency state.

Rest and digest –

Once the threat is removed, the body then is able to rest and recuperate by switching into parasympathetic activity in the nervous system when it relays the signals from the brain to slow the breathing and heart rate. The main hormone involved in this is acetylcholine.  

The digestive and immune system functions resume. This is why the relaxation state is known as ‘rest and digest’. The parasympathetic mode is where our body is able to repair itself and hormones resume regular functioning, including the release of sleep inducing hormone melatonin.

Quick fact – the body can only be in one nervous system mode at a time, e.g., you are either in stress fight, flight, freeze mode (sympathetic activity) or in relaxation rest and digest mode (parasympathetic activity). So, learning to recognise the interplay between the two modes can be helpful for recognising and managing stress.

Stress and health –

It’s easy to see why stress plays such a big role in both physical and mental health. Not only does chronic stress increase the risk of developing health conditions, but it can also aggravate and exacerbate symptoms of disease making it more difficult to manage.

Common conditions impacted by stress include:  

  • Digestive issues such as irritable bowel disease, nausea, gastroesophageal reflux disease and nutrition deficiency.
  • Obesity
  • Asthma
  • Diabetes
  • Heat disease
  • Insomnia
  • Muscle tension and chronic pain.
  • Anxiety and panic attacks
  • Depression
  • Fatigue
  • Alopecia
  • Arthritis
  • Migraines
  • Headaches
  • Skin conditions such as acne, eczema and psoriasis.

For more information – check out my post on psychoneuroedochronology (psycho-neuro-endo-chronology)

Panic attacks can look similar to cardiac events, always stay on the safe side and get it checked out. Please check any changes with your GP and healthcare provider and for sudden onset of symptoms call the emergency services. For more information on heart health and support, see the British Heart Foundation.


Natelson B. H. (2004). Stress, hormones and disease. Physiology & behavior, 82(1), 139–143.

McEwen B. S. (2017). Neurobiological and Systemic Effects of Chronic Stress. Chronic stress (Thousand Oaks, Calif.), 1, 2470547017692328.

Rohleder N. (2019). Stress and inflammation – The need to address the gap in the transition between acute and chronic stress effects. Psychoneuroendocrinology, 105, 164–171.

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7 months ago

[…] We know that our stress response relayed through our nervous system interacts with our hormones and prevents the release of melatonin, which is one of the chemicals responsible for sleep. See my blog on the fight, flight, freeze response for more information on the physiological mechanis… […]

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