person's reflection

Our reptilian brain and our stress response

In my last article, we discovered our stress response.

“Fight = anger”, “flight = fear” is the same stress response our hunter-gatherer ancestors experienced when they came face to face with wild animals threatening their lives. So, has our hunter-gatherer stress response evolved to be more compatible with the technological world we live in today?

Evolutionarily, we generally evolve to suit our environment. In the words of Professor Joseph LeDoux in his book The Emotional Brain: “In a relatively stable environment, it is generally a good bet that the dangers a species faces will change slowly. Since our environment is very different from the one in which our ancestors lived, our genetic preparation to learn about ancestral dangers can get us into a lot of trouble, as when it causes us to develop fear of things that are not particularly dangerous in our world.

“We have the same fear instinct, but our fear instinct creates for us a world of anxiety, depression, exhaustion, phobias and anti-social tendencies.”

Guess this means we’re not coping very well with this technological age.

Technology is developing at lightning speed; today’s breakthroughs are transformed into things we never imagined possible. This disturbs our perception of how we see our world developing. As humans, we need to be able to understand the environment we live in. Why? Because if we don’t feel safe, we automatically trigger a stress response.

I’m not telling you this to create more stressors; I’m telling you this to explain how our foundations are laid and how we can work with these foundations to achieve a better quality of life, without anxiety, depression, exhaustion, phobias, stress, burnout and anti-social tendencies. So, let’s explore what links us to our ancestors – our reptilian brain, what it does and how it functions in our world today.

Our reptilian brain controls our Autonomic (automatic) Nervous System. This system keeps the heart beating, regulates blood flow, separates waste, organises waste disposal, controls digestion, blood pressure, hormonal system, breathing, emotions and much more. Are you getting the gist here?

Our reptilian brain controls all our automatic, unconscious, basic survival functions, including our stress response system; functions we never have to think about.

The scientific name of our stress response system is the Sympathetic and Parasympathetic Nervous System. The sympathetic system fires us up by increasing our breathing; the parasympathetic slows us down by decreasing our breathing. In other words, this is where our stress response is activated and deactivated.


Evolution layered our brain. Forming the floor of our brain, our reptilian brain is the oldest part and the least developed. It occupies roughly 5% of our total brain mass and is associated with primitive behaviours; aggression, protection and ritual displays. It likes to feel safe; it doesn’t like the unknown and can make it very difficult for us to take on challenges and achieve our goals. Explains a lot, doesn’t it?

It consists of four parts. 1) The Cerebellum maintains proper balance and muscle coordination; 2) The Basal Ganglia processes information on body movements and executes proper bodily actions. Think about how you drive a car; this is the part of your brain that automatically does what you need to drive the car; 3) The Reticular System regulates sleep and wakefulness and filters all data received from your senses. Think about how much information your senses pick up every second of the day; 4) The Brain Stem, as well as regulating breathing, its main task is to serve as a circulation pathway for all sensory pathways except olfactory (smell) and visual pathways. It has four parts; I won’t bore you with the details, I’ll just say its like a buffer zone where all sensory information is lined up to be sorted by your Reticular System, except visual and smell.

Because waiting in line can cost lives, primal smells like fire and visual danger signals go straight to your reptilian brain and immediately trigger a fear response. Our olfactory (smell) and visual systems work together; it’s important to see the danger if we cannot smell it.

Recap: After picking up your stressors, your reptilian brain increases your breathing, activates physiological, biological and psychological changes; strengthens your muscles and dictates your actions; fight or flight. Are you putting the pieces together?

This is an automatic unconscious system. Anger and fear are the only options. You have no control, and right next to your stress response is where your reptilian brain regulates sleep and wakefulness. Are you understanding how everything is connected?

So, why do I think it important for you to get to know your reptilian brain? Knowledge is power. Understanding that this is where every one of your stress responses are triggered in reaction to all your real or perceived emotional, physical, psychological and behavioural stressors.

The most primitive, automatic unconscious ancestral part of your brain that regulates your emotional, biological, psychological and behavioural stress responses, in a system in which you have no control, is very important. Let this sink in.

So, have we evolved since our hunter-gatherer days? Our stress response is the same, but our reptilian brain is only the first layer. Over time, two more layers evolved, the Limbic System, our emotional brain, and the Neocortex, our rational brain. This is where we find control.

Can we change our foundations? No, but, with knowledge, we can change ourselves. We are programmed to adapt to our circumstances. When we understand there is an imbalance between our stress response and the evolutionary tools we use to deal with this response, we can adapt.

We have all the tools; we just need to remember they are not all in our reptilian brain. We should make an effort to access them “manually” in other parts of our brain. When we do this, we not only gain control, we achieve a better quality of life without anxiety, depression, exhaustion, phobias, stress, burnout and anti-social tendencies. The Parasympathetic is the key.

By Joan Maycock

Joan Maycock MSc Health Psychologist. Mediator, Consultant, Trainer and Stress and Burnout Programme Developer. Providing one-on-one stress and burnout sessions and stress and burnout educational workshops designed to get everyone thinking about reducing, preventing and managing stress and burnout.

Mind Synergy Int.

915 793 592 | [email protected]