The Physiology of Shock

Fight or Flight Response & Delayed Pain Reaction

The moment our brains perceives danger, it activates the sympathetic nervous system (SNS). This is the part of our autonomic nervous system that controls our involuntary body functions. The SNS triggers the adrenal glands to release adrenaline and noradrenaline. These hormones prepare the body to either fight the threat of flee from it:

-      Increased heart rate and blood pressure

-      Rapid breathing

-      Energy mobilisation

-      Heightened senses

-      Reduced pain sensitivity

This response is excellent for short-term survival.

When I was involved in a car accident, this response allowed me to ask for help and explain the details what had happened. I wasn’t aware of any pain and I did not even consider the connection between the damage to my car and the damage I may have done to my body. This reduction in pain sensitivity also supported me in the moment.


Delayed pain reaction, often experienced after traumatic events, is a direct consequence of the fight-or-flight response.

Endorphin Release

During a traumatic event, the body releases endorphins, which are neurotransmitters that act on the opiate receptors in the brain to reduce pain perception. This is why you might not feel pain immediately after a car crash, even if you have sustained injuries.

Adrenaline and Noradrenaline

These hormones not only prepare the body for quick action but also temporarily suppress pain signals. The heightened state of alertness and energy can mask pain and other physical symptoms.

Focus on Survival

The body's primary focus during a traumatic event is survival. All non-essential functions, including pain perception, are minimised to allow the body to concentrate on dealing with the immediate threat.

Aftermath of the Event

Once the perceived threat is gone, the levels of adrenaline and endorphins start to decrease. This can lead to the gradual return of normal body functions, including the sensation of pain.

Rebound Effect

As the endorphins and adrenaline wear off, the pain that was initially masked can start to be felt, often leading to a delayed reaction where injuries become more apparent hours or even days after the event.


Understanding this physiological response is crucial, not only for recognising your own delayed reactions to trauma but also for helping others who might be experiencing similar delays in their physical and emotional responses. As a therapist, acknowledging the link between physical and emotional reactions to trauma can enhance your ability to support clients through their recovery process. This knowledge emphasises the importance of a holistic approach to trauma therapy, addressing both the immediate and delayed effects on the mind and body.

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