General Adaptation Syndrome
If some of the terms used below such as sympathetic nervous system, hormones, pituitary, etc are unknown to you, you might prefer to read General Information about the Neuro-humoral Regulation first. You can also look up terms in one of several online glossaries.
Seyle has found that stress reaction always goes in three phases and he called the first "alarm phase".
1. Alarm Phase ("fight or flight" response)
What happens in general:
Heart rate, blood pressure and respiration rise in order to supply muscles and brain with more oxygen. More blood is sent to the skeletal muscles and the brain, while blood flow decreases to the stomach, kidneys, skin and liver. Sexual and immune functions are suppressed. Hormones acting as natural opiates are released, in order to relieve potentially existing pain. Natural fats and sugars are actively produced to supply the organism with extra energy. Senses become sharper. The organism activates those systems crucial for an immediate physical response and decreases the energy supply to those organs, which are not so important in a state of emergency.
In short the sympathetic nervous system is stimulated. It should be noted however that some people tend to respond in just the opposite way in a stressful situation. In their organisms the parasympathetic system is stimulated, hence the symptoms are opposite - low blood pressure, slower respiration rate, muscles are too relaxed, fits are possible. However the majority of people respond to stressors with activation of the sympathetic system.
What happens in the body?
The hypothalamus -part of the brain controlling the autonomic nervous system secretes two neurohormones - corticotropin-releasing hormone(CRH) and thyrotropin-releasing hormone(TRH) which stimulate the pituitary gland to produce hormones. In the case of stress the pituitary influences the work of all glands. Some of the hormones it releases will stimulate certain glands to produce more hormones and other to produce less hormones. For instance the pituitary secretes adrenocorticotropic hormone(ACTH) which stimulates the adrenal glands(the adrenal glands are part of kidneys) to secrete corticoids: adrenaline, noradrenaline, cortisone, cortisol. The thyroid gland is stimulated by the thyroid-stimulating hormone(TSH) to secrete thyroxine. Another example are secreted gonadotrophins which stimulate the reproductive glands to produce less hormones. What quantity of each kind of hormones the pituitary will secrete depends on the power of the stressor - the more dangerous the brain perceives it, the more stimulated the pituitary will be. The secretion of corticoids is most characteristic of the stress response. The adrenal gland is stimulated also by the nervous system, which arouses reaction immediately. Adrenaline and noradrenaline are the hormones which cause quicker heart rate, higher blood pressure, more frequent breathing. Cortisol and cortisone suppress the immune system. Fear triggered by adrenaline is one example. The corticoids have significant effect on emotions, as well - for instance, adrenaline injected into a person who is not under stress would cause him to feel fear, even though he will not be able to explain the reason for that fear.
Only after the secretion of adrenaline, in case of injury secretion of endorphins may. Endorphins are produced by the brain and act as natural opiates - they have robust effect on relieving pain and cause positive emotions. Sport activities are a natural means for stimulating secretion of endorphins.
As soon as we see or feel something which threatens(or enjoys) us too much, in our organism a set of physiological reactions called stress begins. These reactions are "turned on" without our will; once the mind has perceived what we see or hear or remember as dangerous, the stress reaction begins and we cannot stop it by our will. Simultaneously we begin to think how to tackle the emerged threat. We shall study the physiological reactions and thinking separately, although both processes happen simultaneously and interact with each other.
If an individual is subjected to frequent and strong stressors this may cause severe endocrine disorders. The humoral feedback does not influence directly the pituitary, but other parts of the brain first. Oversecretion of hormones may adversely affect brain tissue, which on turn would fail to send proper signals to the pituitary. The whole process turns into a vicious cycle, which can become a reason for severe endocrine (and mental) disorders. Once the organism is subjected to endocrine disorders the stress reaction does not take its normal course and may lead to life-threatening conditions. A tumor of the pituitary can cause overstimulation of hormone production, which on turn can cause shock.
The alarm phase lasts for seconds, it may last even less than a second(adrenaline secretion and manifestation of its effects alone, take less than a second). In the second stage of the stress reaction, adaptation, the pituitary stops that large secretion of hormones and the effects of the alarm phase lessen. The actual relaxation of the organism, however (sympathetic and parasympathetic systems return to normal balance) happens much later. The symptoms of the alarm phase continue long after the stressor has disappeared. During adaptation the organism adapts to the stressor - if there is high noise for example, little by little we get used to it and it does not irritate us that much. Nevertheless we continue to feel it as stressor. Another example is adapting to a threat - suppose someone has tried to rob you on the street. After the initial panic you will "adapt to the robber" - he will not look to you that fearsome and the feeling of fear will soon be swapped by reasoning whether and how to fight or flee. You will no longer care about the aggressive impression he makes by his look and voice, but rather you will care about his actual actions and motives. We adapt not only to harmful stressors - after hearing a good news we react with joy in the first moment but gradually we calm down and the feeling of happiness is not so strong. Whenever you deal with a stressor you get to know it better and next time your organism and your psyche will be better prepared to tackle it. It is easier for the organism to adapt to a stressor if it appears rhythmically. Adaptation to pain has been observed in individuals who suffer chronic diseases, with pain appearing in definite intervals.
Seyle introduces the term adaptation energy. It means that everyone's organism has finite resources to adapt to stressors, and whenever it has to adapt it loses "adaptation energy", that is next time the organism will have less resources to adapt. Adaptation energy, according to Seyle cannot be gained; its amount is determined by birth and the best we can do about it, is to use it efficiently so that minimum adaptation energy be lost "per stressful event". Seyle even suggests that loss of adaptation energy might be explanation of aging.
Studies have found that if someone had suffered a disease and he suffers the same disease again, his organism is better prepared to cope with that disease. The case is not the same, however with an aging individual. This may provide some grounds to think that the loss of adaptation energy does not result in less successful adaptation every following time - the organism adapts 100% after stress as long as it has enough adaptation energy to do so; the adaptation energy diminishes with every stress suffered, while a moment comes when the person is stressed again but there is not enough energy to cope 100% and with every further stress the adaptation is less and less successful.
Correct interpretation of the term adaptation energy is hard because adaptation energy refers to something not tangible but to something, which is the effect of a process, something which should exist because statistical data suggests so. We cannot see it or feel it to say whether it exists or not; we have to follow logic and compare experimental data to determine whether such thing can exist.
If you are a professional acquainted with modern research on the subject do not hesitate to add your expert knowledge. Your opinion will be much appreciated.
Considering the psychological reaction of a person under stress, Seyle concludes that there are three ways in which one can sensibly react to a stressor - adaptation, fight or fleeing. If we have to deal with a real situation -we can either adapt to the problem, that is we agree to bear its negative consequences; we can fight - that is to deal with it, eliminate it; or flee - escape from the problem. When coping with a stressor it is crucial for us to choose the proper strategy.
Adequately estimating which strategy is most appropriate can be an arduous, even impossible task under stress. Concentration abilities are seriously deteriorated during the stress response and it may be vital for an individual to react in any way as quickly as possible rather than wasting time thinking which strategy is best. In the chapter "Take Control of It" we will discuss various effective coping strategies.
The last stage of the stress reaction is exhaustion. Since the organism has depleted much of its reserves, one feels exhausted, he has no strength to deal with the stressor any more and the necessary recreation follows. If the stressor is too strong exhaustion may mean death.
Otherwise, the organism recovers fully in the course of time. Only prolonged, too frequent, or too strong,(hyper)stress reactions can cause permanent disorders either to the body or to the psyche.
suggest additional material/new interpretations on the subject