Firstly, not all stress is bad. We know that a healthy amount of stress can increase performance. Think of the nervous energy that an athlete needs to get focused and sharp to get off the block fast – that’s performing enhancing stress.
But what we know is that stress reaches tipping point – we often call it the fight-or-flight response. It’s the brain’s activation of our sympathetic nervous system which initiates a series of changes that we experience in our mind and body.
This system in our body is very old and evolved to serve our ancestors at time when the stressors that humans faced were pretty different to those that we commonly experience today.
1. Stress increases heart rate and also changes where our blood is predominantly going to in the body.
When the brain is in a stressed state it prioritises getting blood to organs and muscles that our ancestors needed when they encountered stress. So we see an increase in blood flow to the lungs, brain and large muscle such as legs and arms as well as the sense organs – our eyes, our ears, our nose.
We only have X-amount of blood in our body at any given time, so more blood to these areas means less to others. During stress the brain deprioritses blood flow the skin – causing us to feel clammy as well as cold hands and feet.
Blood flow to the digestive system is also limited which we can experience as nausea or ‘butterflies in our tummy’, as well as digestive problems, diarrhoea and constipation.
Interestingly, a secondary effect of our digestion having less blood supply is that we produce less saliva which explains why many people experience a dry mouth due to stress and anxiety.
2. Stress Surpasses Logical Thinking
When we’re stressed our brain activates the more primitive and emotional region of our brain – known as our limbic system – more than our more complex higher brain centers.
Our limbic system is the seat of emotion and reaction. When activated during stress, it overrides more rational parts of the brain and suppresses concentration, short-term memory, rational thought, and inhibition. We can act without the regulating effect of wisdom, memory or judgment. Logic is simply unavailable in the moment, and reactions are based on raw emotion.
The biological function of all this allows you to engage fully in fight or flight without your thinking brain intruding and this is good if you’re needing to escape from a predator.