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  • Jade Cunningham

Fight Or Flight

Updated: Sep 10

One question I ask a lot of clients is ‘have you heard of the fight or flight response?’, and the answer is normally yes. But if I ask if they know what it actually is, the answer is almost always no.


Every single one of you reading this will have experienced this response, and you’ve probably experienced it more than you realise. In the short term, it's very important and helps prepare our bodies to react in a way that keeps us out of immediate danger. However, remaining in this state for long periods of time starts to have a detrimental effect on our health.





Your nervous system is made up of many different branches and sub branches that all play a different role in keeping you alive. The central nervous system (CNS) is made up of the brain and spinal cord, and the peripheral nervous system consists of all the nerves that branch out and supply the body. The autonomic nervous system (ANS) is part of the peripheral nervous system, and is further broken down into three distinct systems.


The sympathetic nervous system (SNS) covers almost the entire body and is responsible for the ‘fight or flight’ response. It is responsible for the regulation of blood vessels, leading to vasoconstriction of most blood vessels with the exception of coronary vessels and those supplying skeletal muscles. This means that blood is diverted away from non-essential organs and functions, so that the heart and skeletal muscles have a larger blood supply in times of stress, making it easier for us to fight or run away. It's also active during non-stressful situations, and plays a role in airway dilation during normal respiration, allowing more air to enter the body.


Another function of the SNS is regulation of the immune response, as it innervates organs like the spleen, thalamus, and lymph nodes.This means it plays a role in the inflammatory process. During periods of prolonged stress, cortisol levels in our bodies increase, which is the hormone responsible for inflammatory and immune responses in the body. Increased levels of this hormone eventually leads to our tissues becoming desensitised to it, which results in increased inflammation, and tissue inflammation becomes a chronic condition as a result of chronic stress.


The parasympathetic nervous system (PNS) does the opposite of the SNS, and is responsible for the ‘rest and digest’ state. This is where our body is functioning normally in the absence of a stressor. Around 75% of the PNS is made up from the vagus nerve, which has a direct impact on cardiac function as well as digestion. It is responsible for slowing heart rate and reducing blood pressure to normal, as well as increasing salivation and peristaltic activity, meaning the involuntary muscles of the gut return to normal function. Like the SNS, the PNS is also active during respiration, but its role is to keep the airway rigid so that it doesn't collapse as we exhale.


The third part of the ANS is the enteric nervous system (ENS) and communicates with both the SNS and PNS. Its main function is in digestion, controlling the contraction and relaxation of muscles, secretion and reabsorption, and blood flow. It works through reflexes, and also helps regulate heart rate and the immune system.


If you want to find out more about how your nervous system works, or think you're stuck in a state of chronic stress, book in for a free discovery visit to find out more about how we can help you!


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