I learned this today. Fight or flight, the stress response, was first described by Walter Bradford Cannon in 1915.
In 1915, Cannon published Bodily changes in pain, hunger, fear and rage. He noticed that when cats were threatened, their bodies released the hormone adrenaline / epinephrine, which lead to a series of other bodily changes. He noticed that these changes were automatic, and they were aimed at helping the cat to survive a dangerous situation by either running away or fighting. He came up with the term fight or flight.
The stress response starts in the amygdala. This is the part of the brain that is responsible for memory, decision making, and emotional responses. The amygdala receives information from the eyes, ears, and other senses and makes the decision that there is a dangerous situation. It sends an electrical signal to the hypothalamus.
The hypothalamus is the control center of the autonomic nervous system and can control the release of hormones from the pituitary gland. It controls body temperature, hunger, attachment behaviors, thirst, fatigue, sleep, and circadian rhythms. The hypothalamus reacts to the signal from the amygdala and releases adrenocorticotropic hormone from the pituitary gland and epinephrine from the adrenal gland.
(As an interesting aside, adrenaline and epinephrine are two names for the same thing. In 1897, American physician John Jacob Abel isolated adrenaline and decided to call it Epinephrin. This is the name that is used in America. In 1901, Jokichi Takamine patented a purified adrenaline extract and called it adrenaline. This became the name in Britain and Europe. Different names for the same hormone in different countries.)
The release of epinephrine triggers the production of the hormone cortisol. Cortisol increases blood pressure, blood sugar, and suppresses the immune system. The epinephrine binds to liver cells and increases the production of glucose, creating an extra source of energy. The cortisol also works to turn fatty acids into energy, giving your body access to its fat stores as another source of energy.
The cortisol increases the heart rate, pumping more blood to the muscles, and other vital organs. It also causes blood vessels to constrict. The blood clotting function of the body speeds up in order to stop excess blood loss in event of injury. Breathing rate increases, taking in more oxygen. This oxygen is sent to the brain, increasing alertness, and the muscles. Muscle tension increases, providing extra speed and strength. Non necessary bodily functions shut down so that their energy can be used elsewhere. Digestion stops, and blood is shunted away from extremities. Sometimes the bladder and sphincter relax. Endorphins are released to manage pain. All of this is getting your body ready to run away or fight.
The fight or flight reaction is instantaneous and happens before we are even aware of it. Once the danger has passed, after about twenty minutes, levels of epinephrine and cortisol should fall back to normal levels. However, sometimes the danger doesn’t pass. In this case, the hypothalamic-pituitary-adrenal axis (HPA axis), keeps releasing adrenocorticotropic hormone, which keeps the adrenal glands producing cortisol. This keeps energy levels high to avoid the dangerous situation. The problem is that the body cannot sustain that amount of energy for very long. People burn out. People in a warzone, for example.
We have evolved this fight or flight response, the same as all animals, to avoid dangerous situations. The trouble is, we don’t have that many dangerous predators in our lives anymore. We have started to see other situations as dangerous, such as presentations at work. These types of dangers are much more ambiguous, and our brains don’t know when we are really under threat. That means we can experience this stress response a lot more often. Some people can even permanently enter the state where the HPA axis is producing adrenocorticotropic hormone and cortisol. Living with this can cause other illnesses. It can damage blood vessels, increase blood pressure, raising the risk of heart attacks and strokes, deplete energy, increase fat build up, and suppress the immune system.
So, the fight or flight response was first coined in 1915. It is the system by which our body prepares us to get out of a dangerous situation. Our brain causes our body to produce epinephrine and cortisol to create an energy source and increase blood pressure, along with other changes. It is vital for our survival. And this is what I learned today.
Photo by Cats Coming from Pexels
Sources
https://en.wikipedia.org/wiki/Fight-or-flight_response
https://en.wikipedia.org/wiki/Walter_Bradford_Cannon
https://www.health.harvard.edu/staying-healthy/understanding-the-stress-response
https://en.wikipedia.org/wiki/Hypothalamic%E2%80%93pituitary%E2%80%93adrenal_axis
https://en.wikipedia.org/wiki/Amygdala
https://en.wikipedia.org/wiki/Hypothalamus
https://en.wikipedia.org/wiki/Adrenaline