Stress is a physiological neurohormonal reaction to external and internal influences, aimed at elimination of consequences of "damaging" factors, leading to disruption of the integrative activity of the brain and other systems of the body, and consequently to a decrease in certain functional capabilities of the person. Physiological stress was first described by Hans Sellier. He believed that "complete freedom from stress means death".
Stress can be caused by three main reasons:
- if a person's desires do not coincide with his or her abilities;
- if the external circumstances are such that a person has to change his or her whole life;
- if the person is affected by external, unusually aggressive factors related to the threat to life.
Hans Selliers described three stages of stress:
- “anxiety reaction” (accompanied by mobilization of neuroendocrine mechanisms (secretion of andreno-corticotropic hormone (ACTH), adrenaline, glucocorticoids increases);
- “Resistance stage” (characterized by restoration of balance between catabolic and anabolic reactions (secretion of anabolic hormones such as somatotropic hormone and insulin increases);
- The “stage of exhaustion” (develops when adaptive reserves are exhausted (the outcome may be the failure of adaptive mechanisms, the development of the disease or even death)).
The causes of stress (or stressors) are divided into two groups: physical and mental.
Physiological and psycho-emotional stresses are accordingly distinguished. At the same time, under the same conditions, stress may occur differently in different people, which, first of all, is determined by adaptation possibilities of a concrete person. It should be noted that an important role in the activity of anti-stressor mechanisms of the human body is given to sleep.
Sleep is a special genetically determined state of the organism, characterized by a natural sequential change of certain polygraphic patterns in the form of cycles, phases and stages. During one night a person usually goes through 4-6 sleep cycles consisting of different stages, which are characterized by a certain number of corresponding sleep phases (one such cycle lasts approximately 90 minutes). The structure of sleep is characterized by a slow sleep phase (anabolic function) and a fast sleep phase (information processing, creation of a behavioral program). Sleep and wakefulness periods in a person change with circadian periodicity. The period of circadian rhythms is usually close to 24 hours. The hormone regulating the circadian activity of the organism is melatoninin.
Currently, it is the adaptation (anti-stressor) sleep system that determines the degree of resistance of the body to various stresses. Its capabilities allow optimizing the body's adaptation to the environment during sleep and partially determine the stress resistance in general. The peculiarity of this system is that it actively works during the whole time of sleep, even in the absence of the action of the stressor.
Stressful reaction begins in awakening and continues during the night's sleep, and with prolonged exposure to the stressor - for several cycles of sleep-warming. The strength and direction of stress during the waking period is determined by a combination of both the strength of the stressor and the individual characteristics of the person (biological and psychological factors). Non-specific manifestation of stress is characterized by increased activity of ascending activating systems of the brain and is manifested in an increase in the representation of waking up during sleep and instability in maintaining the functional state of sleep. Various specific changes in sleep depend on the type of exposure and initial resistance of the body. These changes can be found not only in the intracorporeal but also in the posterior stage (a few days after the end of stress), which may cause the development of insomnia in the future. This leads to a "vicious circle" when stress causes insomnia and insomnia further increases stress.
Short-term stress exposure leads to episodic insomnia (up to one week). A study was carried out to study the main tendencies of changes in sleep structure under the influence of experimental conditions of short-term "isolation" (psycho-emotional stress). So, in the conditions of experiment there was a change of a base cycle of sleep-warming in comparison with an initial condition (the basic changes consist that subjects began to go to bed late (at 1 o'clock 15 minutes), time of falling asleep has