The Stress Response
Also called the fight or flight response it is a vital and intelligent response that has developed to give us the best chance of surviving immediate danger. It gets your body ready to fight or run away from the danger.
Unfortunately, if it is activated for long periods, it can harm our health so we need to eliminate unnecessary stress and find ways of not overreacting to the ongoing non-life threatening stresses in our daily lives.
FLIGHT (PAYING DEAD)
Receptors or sensors in your eyes, ears, nose etc. are constantly picking up information about your situation and sending the information, via the nerves, to the brain. A part of the brain, called the Amygdala, involved with emotional processing interprets the information. If the amygdala interprets the situation to be dangerous, e.g. a car is hurtling towards you, it will immediately sound the alarm by sending a distress signal to a close neighbour in the brain called the Hypothalamus.
The sympathetic nervous system functions like accelerator in a car. It triggers the fight or flight response, providing the body with a burst of energy so that it can respond to perceived dangers. The parasympathetic nervous system acts like a brake. It promotes the "rest and digest" response that calms the body down after the danger has passed but is downgraded during the stressful period.
After the amygdala sends a distress signal, the hypothalamus activates the sympathetic nervous system by sending signals through the autonomic nerves to the adrenal glands. These glands respond by pumping the hormone adrenaline into the bloodstream. As adrenaline circulates through the body, it brings on a number of physiological changes. The heart beats faster than normal, pushing blood to the muscles, heart, and other organs vital to fighting or running to evade the danger. At the same time blood is diverted from organs, like your digestive system, whose function are not essential, in the short term, to survival.
The hypothalamus then takes over and acts as an emergency control center. Because the wiring between the amygdala and the hypothalamus is so efficient you are able to jump out of the way before the visual centres in the cerebral cortex of your brain have even fully interpreted the situation.
The hypothalamus communicates with the rest of the body through the autonomic nervous system, which controls such involuntary body functions as breathing, blood pressure, heartbeat, and the dilation or constriction of key blood vessels and small airways in the lungs called bronchioles. The autonomic nervous system has two components which work together to enable your body physiology achieve the optimum balance for a given situation.
Fight or flight
Pulse rate and blood pressure go up. The person undergoing these changes also starts to breathe more rapidly. Small airways in the lungs open wide. This way, the lungs can take in as much oxygen as possible with each breath. Extra oxygen is sent to the brain, increasing alertness. Sight, hearing, and other senses become sharper. Meanwhile, adrenaline triggers the release of blood sugar (glucose) and fats from temporary storage sites in the body. These nutrients flood into the bloodstream, supplying energy to all parts of the body.
As the initial surge of adrenaline subsides, the hypothalamus activates the second component of the stress response system — known as the HPA axis. This network consists of the hypothalamus, the pituitary gland, and the adrenal glands.
The HPA axis relies on a series of hormonal signals to keep the sympathetic nervous system — the "accelerator" — pressed down. If the brain continues to perceive something as dangerous, the hypothalamus releases corticotrophin-releasing hormone (CRH), which travels to the pituitary gland, triggering the release of adrenocorticotropic hormone (ACTH). This hormone travels to the adrenal glands, prompting them to release cortisol. The body thus stays revved up and on high alert. When the threat passes, cortisol levels fall. The parasympathetic nervous system — the "brake" — then dampens the stress response.
All of the above changes are very positive in the short term, e.g. to dive out of the way of the runaway car before you even think about it. Regular short periods of intense stress, e.g. rollercoaster rides, even seem to have positive long term health benefits. The problem is that we can also overreact to situations which are not life threatening.
Thankfully, very few of us in modern life experience many life threatening situations. However, many of us do tend to over react to less serious stresses that go on for long periods of time, i.e. they are chronic. Years of working under increasing pressure in jobs we don’t enjoy, traffic jams or family difficulties are some of these stresses. When we repeatedly over react to these we will have long term physiological changes. The changes which are beneficial in the short term can be very harmful in the long term if we are not able to learn to cope them.
Over the years, researchers have learned not only how and why these reactions occur, but have also gained insight into the long-term effects chronic stress has on physical and psychological health. Over time, repeated activation of the stress response takes a toll on the body. Research suggests that chronic stress contributes to high blood pressure, promotes the formation of artery-clogging deposits, and causes brain changes that may contribute to anxiety, depression, and addiction. More preliminary research suggests that chronic stress may also contribute to obesity, both through direct mechanisms (causing people to eat more) or indirectly (decreasing sleep and exercise).
Effects of the Stress “Fight or Flight” Response on Our Physiology
Pulse and Blood Pressure
Blood Clotting Factors
Blood Lipids (fat)
LDL (bad) Cholesterol
Fear, Anxiety and depression
Sensory System (including pain)
HDL (good) Cholesterol
Serotonin (happy hormone)
Modern sanitation, hygiene and safety awareness has protected us ever more effectively from the risk of exposure to the physical dangers and infectious diseases which caused the early demise of our ancestors. Furthermore, modern medicine has greatly increase our chances of surviving if we are exposed to the infectious diseases and traumas that might have ended our lives early.
Looking at the list above it is not difficult to see that chronic, or longstanding, stress probably has a major role in many of the disease processes which have emerged as the biggest health issues in modern life, e.g. coronary artery disease, diabetes, thromboses and it has also been known since the mid 1900’s that subjecting mice to chronic stress increased the chances of them developing cancer.