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The neuroscience of stress.

Writer's picture: Eric MahlebEric Mahleb

Visual of the brain, highlighting networks.

The neuroscience of stress.


Animals experience a primal stress response characterised by a fight, flight or freeze response. Human beings experience stress in the same way, and have been since the dawn of time. This primal stress response has helped human beings to survive, learn and evolve.


THE LIMBIC STRESS PATHWAY

In human beings, the primal stress response is characterised by the involvement the 'older' parts of our brain, the brain stem and the limbic system. 


The brain stem, being the oldest part of our brain, focuses primarily on basic and essential functions such as breathing, heart rate and central nervous and stress system regulation.

The limbic system is home to many structures that help to regulate memories, behaviour and much more, including the stress reaction. The key limbic structures involved in the stress response are:


  • The Thalamus picks up a threat in the environment and relays sensory signals to

  • The Amygdala, which 'coordinates' of the stress response and sends signals to

  • The Hypothalamus, which is the link between the nervous system and the endocrine/hormonal system


As illustrated below, these three structures are involved in the release of the two key stress hormones, cortisol and adrenaline. These two hormones, when released, flood the body and organs so that the person can react to a perceived threat in their environment. This is an efficient system that has worked for human beings for a long time and has helped them to deal with what their nervous system perceives as threats in their environment.



A diagram representing the stress process in the body from the brain to the adrenal glands.

Unfortunately, for most people, threats in our environments have changed. Our nervous systems today are being threatened by many things and factors, some of them more real than others. Each person will react differently to the same threats, and therefore, each stress' response is very individual.

Some of the 'threats' today include:


  • A colleague or boss sending you a not very pleasant email or telling you off in a meeting

  • Being passed over for a promotion or not being acknowledged for our work

  • Changing roles and organisational structures

  • Long hours and unrealistic deadlines

  • Digital notifications, FOMO...

  • Noise, traffic...

  • And many more



THE PFC STRESS PATHWAY

In contrast to animals, human beings also have a more modern part in their brain: the pre-frontal cortex. This structure is what allows human beings to shine in analytical and rational thinking, in planning and organising and in making decisions and managing emotional responses.


And while the PFC can help moderate the primal stress response, it can also itself be the cause of stress. 


It is said that the average person generates around 70,000 thoughts per day and that most of these are either repetitive or negative. While this number can not be officially proven, the idea that most of our thoughts are not helpful has been experienced first-hand by most psychologists throughout the world.


Cognitive stress is what happens when our thoughts become so intense and negative that we no longer have control over what is flowing through our heads. This leads to rumination, worry, regret, doubts...While some of this can be useful, most people suffering from cognitive stress are no longer 'in charge' of some of their thoughts and find themselves being taken on negative storytelling journeys that in turn lead to negative emotions and behaviours.


The PFC is not alone in creating this stress response. It relies on the limbic and brain stem systems as well. But in many cases, it can be responsible for the creation of a perceived threat.


A person is able to manifest a danger that may or may not be real and to trigger a very real stress reaction.


A simple graphic of the brain, showing brain stem, limbic and pfc.


The stress response is obviously a very complex process that involves much more than what I described above. However, it is crucial to remember that at the core is a very old and efficient system that is unfortunately being triggered too often by the demands of our modern world.


There are many different methods to reduce and mitigate your stress response. Noticing your thoughts is not a bad place to start.

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