The way we deal with stress hasn’t changed since the days when we were in danger from wild predators and adversaries. Our body needed a way to give us a burst of energy to run back to our cave to escape danger or to have the courage to stand and fight for our lives if fleeing wasn’t an option (or wasn’t in our nature!).Although we aren’t regularly at risk of such dangers anymore, we haven’t lost that same physiological response to a stressful trigger (a stressor). Whatever the stressor, be it a snarling wolf, a venomous snake or a big credit card bill, or a fast-approaching work deadline, the same things happen within our body.In the presence of a stressor, the brain receives information about the threat. The amygdala is alerted first, then the hypothalamus. Next, the pituitary releases an adrenocorticotropic-releasing hormone which causes the adrenal glands to release epinephrine (adrenaline), which primes the body for the fight or flight. Breathing accelerates and blood moves to the brain and skeletal muscles (diverting blood away from areas such as the digestive system and the reproductive organs). In addition, the heart rate increases and the blood pressure rises. Epinephrine makes our pupils dilate to improve vision. During our ancient past, this would have given us the extra boost to either run to safety or fight off a predator, dangerous animal or adversary. That immediate danger would have passed relatively swiftly (you were either going to escape the danger or not!) and once you had, hopefully, found your way to safety the secretion of epinephrine would have dropped away, with cells also lowering their sensitivity to epinephrine. But nowadays, our stressors aren’t always so easy or quick to get away from. Modern life itself can be consistently stressful, even more so for those living with anxiety or depression, conditions which leave the brain struggling to process emotions normally. The body may face periods of stress that don’t pass within minutes or hours and in these cases, the hypothalamus directs a releasing hormone to the pituitary which, in turn, secretes an adrenocorticotrophic hormone (ACTH). ACTH instructs the adrenal cortex to release cortisol which then primes the body to handle the perceived stress, making sure that stored energy within the body is moved back into the bloodstream as sugar, to give the body the fuel to keep going.
Cortisol is also an anti-inflammatory and as such it dampens this natural healing response within the body (in the past this was designed to help you keep on going even if you were injured and trying to escape a dangerous situation). All this helps to keep the body pushing forward to deal with the stressors, but what if the perceived stress doesn’t go away?
General adaptation syndrome is the body’s way of dealing with prolonged periods of stress. After the body has utilized the reactions above, the adrenal glands continue to release cortisol in an attempt to keep the body primed. People who have reached this stage of the stress response can exhibit tiredness, weepiness, anxiety, agitation, poor concentration and can appear very run down. I think many of us can relate to this state, perhaps following a stressful, busy spell of work, during exams, or when going through a financial or relationship issue. If stress continues past this point, and an individual can’t find a way to relax and rest, the final stage in the stress response will occur- exhaustion.An individual with true exhaustion has completely depleted their energy resources and their immune system is often depleted too. They are mentally fatigued, physically exhausted and they often start experiencing poor health, with an endless cycle of infections.
Throughout the stress response, the sympathetic division of the nervous system is in charge. To counteract all these physiological responses the body needs to shift gear, allowing the parasympathetic nervous system to take over. When it does, the body can slow down and focus on digestion and healing. Much of the current advice regarding the management of stress in our lives is given because it encourages that shift to parasympathetic stimulation. Activities such as yoga, meditation, mindfulness, coloring-in, reading, walking, socialising – it all encourages the mind and therefore the body to relax by entering the parasympathetic ‚gear‘.
When we are under stress (and therefore under the control of the sympathetic nervous system) our digestive systems do not receive the same supply of blood as they would under parasympathetic control. Digestion and absorption cannot be as good when we are stressed because the digestive tract isn’t being delivered the optimum amount of blood to nourish the digestive organs and to transport nutrients away. Furthermore, we are all too aware that stress can cause upset within the digestive tract, with symptoms such as excess acid, diarrhoea and IBS being linked to both short- and long-term stress.
In the next module, you will learn much more about how the brain communicates with the digestive system, but before you move on to that subject you will take some time getting to know a rather enigmatic and intriguing system which perfectly highlights the incredible link between gut and brain – the endocannabinoid system.
