It has long been known that sleep is an active process. We fall asleep because brain areas such as the hypothalamus, thalamus, and frontal lobes increase their function. In this state, the activity of the sleep center located in the brain stem is enhanced.
Sleep is closely associated with the daily rhythm of the body alternating day and night, light and dark. During sleep, there is an update and accumulation of energy and functional reserves of the human body.
People sleep around a third of their lives. Events and activities during the day affect sleep at night and well-being the next day. The more a person is awake, the longer he needs his sleep. Sleep performs the so-called homeostatic function, removing the feeling of fatigue, stabilizing the state of the body. Although so far it has not been possible to reveal the true purpose of sleep, but it is known that without it a person does not survive. It was found that the longest period that a person has endured without sleep was 11 days. Fully sleep-deprived experimental animals died.
Considering the above, it becomes clear that sleep disorders are harmful to humans. Insomnia needs to be studied, diagnosed and corrected.
What causes healthy sleep and what happens when it is disturbed? This is important to know because the information obtained will help to understand the causes of insomnia in each particular case and its extortion, to avoid the mental and physical effects of a sleepless night.
So, normal healthy sleep consists of two different phases. Each of them corresponds to a certain picture of physiological parameters that can be registered with a sleeping person in the laboratory with the help of equipment. In a dream, the electroencephalogram (EEG) of the brain varies in frequency, amplitude and spatial distribution of electromagnetic waves in the brain. In addition, the sleeper appears or, conversely, the movements of the eyeballs and muscle tension disappear.
The first phase of sleep is called sleep of the slow movement of the eyes (MDG-sleep). During this phase, the body begins to fall asleep gradually, plunging into a deep sleep.
The first phase consists of four stages of sleep. The first stage is a shallow sleep, during which a person is dormant – still awake, but no longer awake. At the same time on the EEG appear slower than in wakefulness, waves. The muscles of the chin become active and slow rotational movements of the eyeballs appear.
The second stage of the first phase of sleep is deeper. This is a real healthy dream: the so-called sleep spindles are recorded on the EEG.
The subsequent third and fourth stages of MDH sleep correspond to more and more deep sleep. Physiologists sometimes combine the last two stages of sleep and call it deep or slow sleep, because brain waves have a low frequency.
The second phase of sleep is called sleep rapid eye movement (BDG-sleep) or fast sleep. Almost all night dreams occur in this phase of sleep. At this time, the brain generates fast EEG waves, and eye movements also become faster — hence the name “dream of fast eye movement” or “paradoxical sleep”. Paradoxical because, despite the fact that a person is sleeping, his brain generates the same fast waves as in the waking state.
In the phase of BDG-sleep muscle tension is absent. A person is paralyzed, aside from eye movement, respiration, and heartbeat. It is believed that such motor paralysis is a kind of protective mechanism that keeps from real actions that are seen by a person during a dream. Despite the fact that everyone sees dreams, not every person remembers them in the morning, after awakening. Most likely to remember, waking up during or immediately after the dream. And if the dream continues, the dream plot disappears from the memory upon awakening.
Studies have shown that 75% of night-time falls on MDG sleep, the rest is paradoxical (fast) sleep, in which dreams occur. However, the sleeping person does not remain continuously in each of their phases or stages of sleep. A cycle takes place in which all phases and stages of sleep alternate with each other. This cycle is called sleep architecture. BDG-sleep and MDG-sleep alternately alternate each other during the night with periods of 80 to 100 minutes. Most of the deep sleep occurs in the first third of the night, and most of the BDG sleep occurs in the early morning hours.
Often, waking up in the morning at the stage of BDG sleep, one can experience “sleep paralysis” – a feeling as if it is impossible to move or insurmountable drowsiness. This is a normal sensation during the awakening in the phase of BDG-sleep and do not be afraid of them.
The dream architecture will continue during the day if you decide to have a day nap. This is usually a deep MDH sleep. But if you take a nap early in the morning, then most likely it will be a dream-like BDG dream.
Interestingly, with age, sleep cycles change. For example, newborns spend almost all the time of the day in the phase of BDG-sleep or MDG-sleep. And only by about 6 months of life, more stable cycles of sleep and wakefulness are formed. As a result, the child stops waking up at night, and sleeps less during the day.
By the age of 20, the duration of MDH sleep begins to gradually decrease. As they grow older, older and older people have a shorter duration of MDG sleep and dreams in the phase of BDG sleep. The age-related features of sleep architecture are directly related to the problem of insomnia in children and the elderly.
An important discovery was the fact of the existence of changes in many physiological systems in the human body during sleep. For example, compared with the waking period, in the phase of MDG sleep, the pulse and respiration rate slow down, while the muscles of the body relax. In the phase of BDG-sleep during dreams, heart rate, blood pressure and breathing become unstable and fluctuate. At the same time, control over the regulation of body temperature is lost and therefore the person freezes when it is cold around, or it becomes hot if it is warm in the bedroom.
The endocrine system is very active in sleep, especially for hormones: growth hormone (growth hormone), prolactin, melatonin and thyroid stimulating hormone of the pituitary gland, which are released during deep sleep. Indeed, children grow up at night because growth hormone is associated with deep sleep. The secretion of steroid hormones, on the contrary, occurs in the phase of fast sleep (BDG sleep). The internal temperature of the body also fluctuates cyclically – from the lowest – in the dream early in the morning, to the highest – in the afternoon during wakefulness.
Science has found that the average person needs 8 to 9 hours of sleep per day. Some people have 4-5 hours, and others – 10 or more. Each person can determine for himself how much sleep he needs. To do this, you need to evaluate your optimal performance during the day, depending on the duration of sleep.
If a person does not fall asleep in a dark, quiet room, sitting in a relaxing environment, such as at the TV screen, reading or awake, no matter how boring and monotonous his activity is – sleep is enough; if not, then the state of sleep and wakefulness does not correspond to the generally accepted norm, and attention should be paid to this.
Sleep is considered insufficient if:
– you can not sleep long;
– wake up too often;
– sleep is disturbed by any processes in the body or something happening next;
– after sleep you feel overwhelmed and not rested; – fall asleep during the day at any time and in the wrong place. The most common problems are: 1) poor sleep at night; 2) sleepiness during the day.
We will look at all the major sleep disorders, including the causes and treatment of insomnia. Since there is a very close relationship between normal and abnormal sleep with the individual biological rhythm of a person, this issue will be considered separately.