Table of contents:
- How do we fall asleep
- Activating and inhibitory centers of the brain
- Why is it difficult to fall asleep during stress?
- How stress reduces sleep quality
- Sleep deprivation as a stress factor
- Is it possible to sleep off after stress
Video: Stress is an underestimated danger of losing sleep, family and work
2023 Author: Seth Attwood | [email protected]. Last modified: 2023-11-26 22:42
“You sleep all night, otherwise you will not sleep. This way and that way. I got up, walked around, lay down. He lay down, walked around, got up, "- the song of the Soviet rock group" Sounds of Mu "describes the familiar to many difficulties with falling asleep. This condition most often occurs in response to exposure to stressors. Somnologist Mikhail Poluektov explains why it is so difficult to get enough sleep during times of stress and why sleep deprivation itself is a stressful factor.
People under stress may complain of insomnia. This condition is not characterized by a complete lack of sleep. In any case, a person falls asleep, but this is more difficult for him: he tosses and turns in bed, trying to get rid of obsessive thoughts about an upcoming or an unpleasant event that has already occurred. His sleep may be shallow or intermittent. Therefore, doctors prefer to use the term "insomnia", which implies a subjective feeling of insufficient or poor quality sleep, superficial and intermittent, which affects activity during wakefulness.
Insomnia, which occurs in response to the action of any stressful - most often emotional - factor is called acute, or adaptive. As a rule, it lasts as long as the stress factor is present. After the termination of its effect, sleep is restored.
People with insomnia have an increased activity of the central nervous system. In addition, they are dominated by the activity of the sympathetic division of the autonomic nervous system, which is responsible for the activity of internal organs, glands and blood vessels in a stress situation, both during periods of wakefulness and during all phases of sleep. The activity of the parasympathetic division of the autonomic nervous system, which is responsible for the body's work during periods of relaxation - sleep, digestion of food, and so on - is reduced. The level of secretion of cortisol, a stress hormone that is responsible for activating various systems during stress, rises in people with adaptive insomnia by 20 hours, while in healthy people its production at this time is low, as the body prepares for sleep. This hormone is responsible for activating a variety of systems in stressful situations.
How do we fall asleep
At each moment of time, the ability to fall asleep is determined by the level of our lack of sleep, that is, by how much time has passed since waking up, how much fatigue and so-called sleep substances have accumulated in us. It is assumed that the main substance that determines the increase in sleepiness during wakefulness is adenosine. It is a nucleoside that is part of adenosine triphosphoric acid (ATP), a universal source of energy for all biochemical processes.
During work, cells consume a lot of ATP, which degrades first to adenosine diphosphoric acid, then to adenosine monophosphoric acid, then just to adenosine and phosphoric acid. Each time phosphorus residues are cleaved from a molecule, a large amount of energy is released, which serves as fuel for biochemical reactions. When all phosphorus residues are disconnected and all the energy is released, only adenosine remains in the cytoplasm of the cells, which causes an increase in the feeling of drowsiness. Naturally, adenosine, which is released in nerve cells, and not in muscle cells or internal organs, has an inhibitory effect on the nervous system. During the day, adenosine accumulates in increasing quantities, and in the evening a person begins to feel sleepy.
Activating and inhibitory centers of the brain
At the same time, the likelihood of sleep onset is determined by fluctuations in brain activity in the daily cycle. They are due to the complex interaction of several centers in the brain, some of which relate to the system for maintaining wakefulness (the so-called reticular activating system in the brain stem), others to the sleep generation system (centers of the hypothalamus, brain stem and others, there are eight of them in total).
The neurons of the activating zones stimulate the rest of the brain with the participation of neurotransmitters - biologically active substances of various chemical structures. Neurotransmitters are released into the synaptic cleft, and then, connecting with the receptors of the next neuron on the other side of the synapse, cause a change in the electrical excitability of the latter. Neurons of various activating systems have their own mediators and are usually located side by side, in clusters of several tens of thousands of cells, forming wakefulness centers. These neurotransmitters not only stimulate the brain but also suppress sleep centers.
In sleep centers, not an activating, but, on the contrary, an inhibitory neurotransmitter, gamma-aminobutyric acid (GABA), is released. Sleep occurs when the suppressive effect of the activating systems decreases and the sleep centers "break out of control" and begin to suppress the centers of wakefulness themselves.
The work of activating systems is regulated by the internal clock - a group of cells in the hypothalamus, the metabolic cycle in which is on average 24 hours 15 minutes. This time is adjusted every day, as the internal clock receives information about the time of sunset and sunrise. Thus, our body constantly knows what time it is. During the day, the internal clock supports the work of activating structures, and at night it stops helping them, and it becomes easier to fall asleep.
The duration of sleep is determined by the time it takes to restore body functions. As a rule, it is from 7 to 9 hours. This need is genetically laid down: it will take one person 7.5 hours to restore the body, and another - 8.5 hours.
Why is it difficult to fall asleep during stress?
If a healthy person in a relaxed state goes to bed at 12 at night, he has high levels of adenosine in the brain, while brain activity decreases, as dictated by the internal clock. Therefore, he usually manages to fall asleep in less than half an hour (the norm). In a state of stress, sleep does not come for a long time, even if a person has not slept for a long time and a lot of adenosine has accumulated in his body. This is due to the hyperactivation of the nervous system.
Any stress is a challenge to the safety of the body. In response to the action of a stressor, mechanisms are activated that activate the activity of some organs and systems and inhibit the activity of others. The "emotional brain" and neurotransmitters play a key role in the regulation of these processes.
Exposure to an emotionally significant factor leads to the activation of areas of the limbic system of the brain (the part of the brain responsible for emotions), the main element of which is the amygdala. The function of this structure is to compare the stimuli entering the brain with previous experience, assess whether this factor is dangerous, and initiate an emotional response to it. When the amygdala is activated, in addition to generating emotions, the activating systems of the brain are also stimulated. These systems not only activate the cerebral cortex, but also prevent falling asleep, including suppressing the activity of sleep centers.
Norepinephrine is the main activating “stress” neurotransmitter that stimulates the brain and prevents falling asleep. Neurons that contain norepinephrine and support wakefulness are located in the area of the blue spot in the upper parts of the brain stem.
In addition, acetylcholine plays a role in maintaining a high brain tone, the source of which is the basal nucleus of the forebrain (it activates the cerebral cortex), serotonin (neurons containing it can both act on the neurons of the cortex directly and inhibit sleep centers), glutamate and in the lesser degree of dopamine. Also, researchers today pay a lot of attention to orexin, which helps the brain to be in a state of arousal. The function of orexin-containing neurons, which are located in the middle hypothalamus, is unique: on the one hand, they directly activate the neurons of the cerebral cortex, preventing them from "falling asleep", on the other hand, they act on the neurons of other activating systems, being "activators of activators".
If the body is faced with something unforeseen, the activating systems begin to work more intensively than usual, and excite other parts of the brain so that they go into an "emergency" mode of operation. Accordingly, the likelihood of falling asleep is reduced because the brain activity is too high. And although the internal clock at this time dictates the brain to reduce activity, complete recession is prevented by the constant excitation of the activating systems of the brain, which keep it in a hyperactive state.
How stress reduces sleep quality
One way or another, at some point, due to the accumulation of an excess amount of adenosine in the brain, the pressure of sleep overpowers the excess arousal, and after several hours of torment, the person experiencing stress finally manages to fall asleep. But a new problem arises: with excess brain activation, it is difficult to reach deep, relaxing stages of sleep, during which the body recovers physically.
When a person experiencing stress enters the deep sleep phase, they cannot stay in it for long. Due to the excitement of the nervous system, a large number of transitions to superficial sleep states occur. The slightest hint of additional arousal - for example, when a person needs to turn around in bed, while his brain is slightly activated to tell the muscles to change body position - becomes excessive in a state of stress and leads to the fact that the person wakes up and cannot fall asleep again …
Early morning awakenings are also due to cerebral hyperactivity, which interferes with prolonged sleep. Imagine a healthy, stress-free person who goes to bed at 12 a.m. and wakes up at 7 a.m. According to the sleep regulation model, after seven hours of sleep, all the excess adenosine in his brain was used to build new ATP molecules and lost its inhibitory effect. In the morning, the internal clock gives the brain a signal that it is time to activate, and awakening begins. Normally, the sleep pressure stops only 7-9 hours after falling asleep, since all adenosine by this time has time to be processed. Under stress, excess brain excitement overpowers the action of adenosine when it is still present in the brain cells, and a person wakes up earlier, for example, at 4-5 am. He feels overwhelmed, sleepy, but due to excessive brain activity, he cannot fall asleep again.
Sleep deprivation as a stress factor
Sleep deprivation itself is a serious stress for the body - not only in humans, but also in animals. Back in the 19th century, the researcher Maria Manaseina, conducting experiments on puppies, showed that the complete sleep deprivation of animals for several days is fatal. When other scientists began to repeat her experiments in the 20th century, they noticed an amazing thing: the most serious changes in dead animals did not occur in the brain, which, as was believed, needed sleep in the first place, but in other organs. Numerous ulcers were found in the gastrointestinal tract, and the adrenal glands were depleted, where stress hormones are known to be produced today. In other words, animals that were deprived of sleep developed a nonspecific response to stress, expressed in problems with the work of internal organs.
In addition, it has been shown that in humans, limiting sleep time entails a deterioration in cognitive functions: attention, memorization, planning, speech, volitional functions suffer, and emotional response is impaired.
However, when a person has trouble sleeping, he begins to worry about possible health consequences and associated life difficulties, which fuels excess brain activation. The result is a vicious circle, and sleep disturbances can persist for months after the stressful event is over. Thus, sleep disturbances caused by a stressful event become stressful in themselves.
Is it possible to sleep off after stress
At the end of sleep deprivation, when a person gets the opportunity to sleep as much as he wants, the rebound effect occurs. For several days, sleep deepens and lengthens, a person sleeps, as they say, without hind legs. For example, after setting the record for sleep deprivation, schoolboy Randy Gardner (he did not sleep for 11 days) slept for 16 hours, after which he was recognized by doctors as completely healthy. The same changes in sleep can be observed when coming out of a state of stress. When the effect of the stress factor has ended, the brain no longer needs to maintain excessive activity, and nature takes its toll: within a few days it returns back the sleep time that a person lost due to lack of sleep due to stress.
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