PART 2: Chronic stress – The brain concludes that we are continuously in danger

The autonomous nervous system regulates the body functions as situations require. Recovery and healing systems are most active during sleep.  After lunch it is important to digest the food and use the nutrients efficiently. When facing imminent threat, the immune system and food processing are not important. They are shut off, to use all the possible energy for muscles that are needed in the fight.

The autonomous nervous system works largely unconsciously. It is responsible for many vital functions such as blood pressure and temperature regulation, digestion and function of the adrenal cortex.  It works through the neural network that controls the heart and other organs. The autonomous nervous system keeps us alive without us knowingly doing anything about it.

The autonomous nervous system consists of two complementary parts, the sympathetic and parasympathetic.  When active, the parasympathetic nervous system slows down the heart beat, enhances digestion and healing. It strives to calm the body down and keep the vital functions stable.

The sympathetic part is responsible for preparing the body for action, and it´s fibers can innervate tissues in almost every organ.  The sympathetic nervous system activates in stressful situations and in hard physical strain.

The both parts of the autonomous nervous systems normally work in good cooperation, but as a seesaw.  When the other gets active, the other slows down. For instance in acute stress reaction the sympathetic nervous system works in full speed in an instant. The working of the parasympathetic part seizes and e.g. digestion almost stops. A perfect operation of the sympathetic and parasympathetic part enable an accurate and fast regulation of our internal mechanisms in any situation.

The fight or flight response is a way for us to cope in a rapidly escalating threatening situation. At the time of cavemen the case was normally quickly closed, the fights did not last for weeks or months. For a today´s human the stress reaction might be a permanent state, and the parasympathetic nervous system does not have the chance to return our body to rest.

In long term stress the cortisol levels in our body are continuously high

Chronic stress keeps the hypothalamic–pituitary–adrenal axis active. It is like an idling motor, pumping stress hormones such as cortisol to our system.

Cortisol helps us to confront the threat but it simultaneously shuts down the immune system. From the evolution point of view this made sense: if a crocodile attacks we can shut down all the functions in the body that are not needed to flee or fight. The immune defense weakens when we are continuously stressed, and this might lead to a series of infections. The stress factors also play a role in the development of autoimmune diseases, heart and blood vessel diseases and cancer. Continuous boosts of adrenaline can harm blood vessels, raise blood pressure and increase the risk of cardiovascular diseases.

Worrying and fear increase our mental load and can further activate the sympathetic nervous system. Physical symptoms persist,  recovery via rest and sleep further slow down.

Heavy cognitive and emotional load during recovery from an illness might be as bad for our body as physical exercise. Our body would choose to put the work aside when being ill.

Chronic Stress affects memory, concentration and appetite

In a state of chronic stress the brain thinks that a physical fight starts any time. With cortisol our body works to have a lot of energy available. It enhances appetite and extra energy storing  with might lead to weight gain.

Cortisol is also released to hippocampus that is central in memorizing and learning. A stressed out person has difficulties in learning and emotion regulation. There are often concentration difficulties and memory problems.


Chronic stress can not go on forever without consequences. Burnout is a severe disturbance in our vital mechanisms. Simultaneous psychological, neural, metabolic and immune system collapse might be so total, that a complete recovery is very slow or even impossible.

The best cure for burnout is prevention. It can be difficult to understand the graveness of the situation. People tend to compare themselves and their working rhythms to others and to pretend that everything is fine. Just a moment before collapsing things might seem normal from the outside.

Talk with friends and family, colleagues, your superior or a health care professional if you feel  that the load is too high.

Sleep is a good indicator.

Sleep, brain and stress

When the life is in balance, we recover from acute stress reactions and also longer burdensome periods. These take often place in life changes: a newcomer in the family, moving house, study or work project that is exceptionally demanding. We overcome these challenges when the amount of recovery is sufficient.

Sleep is our most important recovery function and an indicator of balance. Weeks and months with disturbed sleep is a sign of stress, and sleep deprivation further lowers down our resilience.

The brain needs sleep. During sleep many things take place that the sleeper is not aware of. A daily cleanup is made in order for us to feel physically and mentally well.

There is no health without sleep. The importance of proper recovery becomes clear after a period of poor sleeping. At worst the life is just coping. Unfortunately this is reality for so many, that we have begun to think it is normal not to sleep enough. But it is not.

When we most nights sleep well and feel brisk in the morning, our body and mind are always prepared to perform well. We are in balance.

The complete set of 5 articles:

  1. Part 1: Fight or flight response
  2. Part 2: Chronic stress – The brain concludes that we are continuously in danger
  3. Part 3: Tools for long term and continuous stress measurement
  4. Part 4: The Moodmetric ring stress measurement and understanding the data
  5. Part 5: The Moodmetric measurement in preventive occupational health 


PART 1: Fight or flight response

Our body does not abandon us when facing a life endangering situation. It prepares us to fight with many tools developed during evolution.

The amygdala is an area of the brain that controls our decision making and emotional responses. It´s tasks include fear processing and threat evaluation based on information from the eyes and ears. From what we have learned, a crocodile presents an extremely dangerous threat, and the amygdala instantly sends an emergency signal to hypothalamus. This area of the brain is like a command center that communicates with the rest of the body, and in an alarming situation activates the sympathetic nervous system.

The fight or flight response is activated by the sympathetic nervous system

The sympathetic nervous system triggers the fight or flight response before we knowingly make any decision on how to act. Many things happen very fast. Firstly the hormone epinephrine (also known as adrenaline) and norepinephrine (also called noradrenaline) are released into our system. We notice the effects: rapid pulse and respiration increase oxygen intake for fast action. Blood pressure goes up and extra oxygen is sent to the brain, increasing alertness. Sight, hearing, and other senses become sharper. Blood sugar (glucose) and fats from energy stores are released into bloodstream to give us the extra power we need.

The skin temperature goes up and sweating of palms makes the grip better – should we need to climb to a tree to flee. Digestion is slowed down – all our energy is now needed to stay alive.

All these reactions are caused by very fast chemical processes in our body. Our preparedness for the fight is uncounscious, and we flee away from the crocodile without thinking.

The fight or flight is a term by Walter B. Cannon

The term flight or flight was first named by M.D.  Walter B. Cannon in 1915. He studied in Harvard and continued to teach there at the department of psychology.  Cannon became especially interested in laboratory animals´ physical reactions under pressure.

When he studied the digestion of scared animals, he observed physical changes in the stomach. Cannon was keen to understand in the relation of psychological and physical reactions for stress and continued his studies on animals´ bodily stress responses for twenty years.

Cannon also re-phrased an earlier presented term homeostasis than means internal balance of the body. According to Cannon our body continuously seeks to gain a certain kind of equilibrium. With living beings the organisms are very complex, including the brain and nerves, the heart, lungs, kidneys and more. For their cooperative condition Cannon suggested a term homeostasis. For instance a raise in blood sugar level makes us thirsty and drinking water re-sets the balance.

‘The homeostatic definition of stress: Acondition where expectations, whether genetically programmed, established by prior learning, or deduced from circumstances, do not match the perception of the environment. This discrepancy between what is observed or sensed and what is expected or programmed elicits patterned responses.’

Still in danger

Let´s get back to the threat we were facing. If the crocodile we saw turns out to be  a soft stuffed toy, we take deep breath and laugh out of relief.

If however the threat is real and a fight is unavoidable, the hypothalamic–pituitary gland–adrenal cortex axis (HPA axis or HTPA axis) activates after the first surge of adrenaline subsidises. The HPA axis keeps the sympathetic nervous system up and running as long as needed, until the fight is over.

The adrenal cortex produces hormones that  contribute to release of cortisol. Cortisol is a steroid hormone that has several functions, it for instance controls the blood sugar level during stress reaction. The hormonal effects caused by the adrenal cortex are called indirect stress responses as they work through blood flow.  These effects take place within 20-30 seconds. Immediate stress responses described in the beginning of this article are induced by the sympathetic nervous system and visible in a few seconds.

Recovery of a stress reaction

When the threat has been removed and the brain no longer perceives the environment risky, will the frontal cortex get an ‘alarm cancellation’ message. The sympathetic nervous system reactions dampen and the amygdala makes the parasympathetic nervous system return the body to its normal relaxed state. The fight or flight response is over.

The body needs about 20 minutes to physically recover from an acute stress reaction. An adrenaline surge affects up to an hour. The release of hormones by the adrenal cortex started later and also lasts longer. The cortisol production in the body will seize as well when the danger is gone, and the balance between sympathetic and parasympathetic nervous system is gained.

The stress reaction can be kept on for a very long time. Human are built to face threats and fight for their lives, normally in rapidly escalating situations that are also quickly over. Activation and preparedness to attack are normal reactions, as well as excitement and joy of victory.

Multitasking, taxes, interests, tormenting colleagues, lost phones and broken household appliances – these were non-existent in the early days of the human species. We can not discharge the surge of adrenaline, when our attacker is a phone bill.

The complete set of 5 articles:

  1. Part 1: Fight or flight response
  2. Part 2: Chronic stress – The brain concludes that we are continuously in danger
  3. Part 3: Tools for long term and continuous stress measurement
  4. Part 4: The Moodmetric ring stress measurement and understanding the data
  5. Part 5: The Moodmetric measurement in preventive occupational health 

The picture and information about Walter Cannon 


What is moodtech? – Science behind Moodmetric

Moodmetric measures the electrodermal activity (EDA) of the skin, which is widely adopted in psychological research 1. EDA is generated by activity of the sweat glands.  Moodmetric measures the palmar skin on your finger. The palmar skin is the recommended EDA measurement location, since it has the highest sweat gland density2.

The unconscious actions of the human body are regulated by the autonomic nervous system. It consists of the sympathetic part and the parasympathetic part. The parasympathetic part controls the body’s rest-and-digest functions and the sympathetic part controls fight-or-flight reactions. When bodily functions are not of interest and the emotional side is, sympathetic nervous system is your choice.

The sweat glands are exclusively innervated by the sympathetic nervous system. This makes EDA an ideal measure for sympathetic activation.2 Electrodermal activity correlates to general emotional intensity, negative emotion, concern, and anxiety. 1, 3 These emotions cause almost similar electrodermal responses, which makes them very hard to differentiate. However, Moodmetric will tell you if certain parts of your day have brought up emotions or not. Inversely, Moodmetric tells you weather you are calm or not. This is particularly useful during your mindfulness, meditation and other calming exercises.

Mobile EDA devices have been used by scientists for some time2, 4, and now we bring this technology within everyone´s reach.

Signal accuracy

The signal accuracy has been proven in a study of 24 people by the Finnish Institute of Occupational Health by J. Torniainen et al.. The accuracy against a laboratory grade reference was found to be 83 %. They conclude:

“Clearly the ring sensor can be used to measure a valid EDA signal as indicated by the similarity of both event-related responses and the calculated features. The accuracy of the Moodmetric EDA Ring is adequate for psychological and physiological research when weighted against the advantage of conducting ecologically valid experiments outside laboratory conditions.”

The results have been accepted for publication in the 2015 conference of the IEEE Engineering in Medicine and Biology Society (EMBC 2015, August 25-29).

Our measurement has been proven to be accurate also by University of Tampere, Finland. The correlation with the reference equipment Nexus-10-MK II was good. Comparison details in charts below.

image1 image2 image3 image4

1 Mendes, W.B. (2009). Assessing the autonomic nervous system. In: Harmon-Jones   E. ja Beer J.S. Methods in social neuroscience. New York: Guilford Press. p. 118-147.

2 Setz C., Arnrich B., Schumm J. and La R. (2010) Discriminating Stress From Cognitive Load Using a Wearable EDA Device. IEEE Trans. Inf. Technol. Biomed. 14(2). p. 410-417.

3 Nikula R. (1991) Psychological correlates of nonspecific skin conductance responses. Psychophysiology. 28(1). p.86-90.

4 Poh M.Z, Swenson N.C. and Picard R.W. (2010) A Wearable Sensor for Unobtrusive, Long-Term Assessment of Electrodermal Activity. IEEE Trans. Biomed. Eng. 57(4). p. 1243-1252.


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