Sleep is a physiological condition that is accompanied by inhibition of consciousness and a slowing of metabolism. In a dream, we spend about a third of life. Sleep is an integral part of a normal circadian rhythm and usually takes a whole night.
Duration of sleep
Sleep and wake patterns change with age. A newborn baby usually sleeps 16 hours a day, and feeding takes place every 4 hours. At the age of one year a child sleeps about 14 hours a day, and at the age of 5 years - about 12 hours. The average length of sleep for adolescents is about 7.5 hours. If a person is given the opportunity to sleep, then he sleeps an average of 2 hours longer. Even in the absence of sleep for several days, a person can rarely sleep more than 17-18 hours in a row. As a rule, a woman needs a little more time to sleep than a man. The length of sleep with age decreases with a minimum age of 30 to 55 years and slightly increases after 65 years. Elderly people are usually withdrawn at night less than young people, but they get the missing time due to daytime sleep.
Sleep disturbance
Approximately one in six adults suffers from sleep disorders, which have an adverse effect on everyday life. Most often people complain of insomnia: they can not fall asleep at night, and during the day they are sleepy and tired. In childhood, there are often episodes of sleepwalking (walking in a dream), which are observed in about 20% of children aged 5-7 years. Fortunately, most "outgrow" sleepwalking, and in adults this phenomenon is rare.
Changes during sleep
During sleep in our body there are a number of physiological changes:
• lowering blood pressure;
• decrease in heart rate and body temperature;
• slowing of breathing;
• increased peripheral circulation;
• activation of the gastrointestinal tract;
• Muscular relaxation;
• slowing metabolism by 20%. Our activity depends on the body temperature, which changes during the day. The lowest body temperature is usually recorded between 4 and 6 o'clock in the morning.
People who wake up vigorously, body temperature starts to rise at 3 am instead of more physiological 5 am. On the contrary, in people who sleep restlessly, body temperature starts to rise only around 9 am. If a man and a woman who lives together have peak activity at different times of the day (one partner in the morning, the other in the evening), there may be conflicts in the pair.
Phases of sleep
There are two main phases of sleep: the phase of rapid sleep (the so-called KSh-sleep) and the phase of deep sleep (non-Yash-sleep). The phase of fast sleep is also called the phase of rapid eye movement, as it is accompanied by active movements of the eyeballs under closed eyelids. At night, the activity of the brain alternately switches from one phase of sleep to another. Falling asleep, we enter the first stage of the phase of deep sleep and gradually reach the fourth stage. With each subsequent stage, sleep becomes deeper. After 70-90 minutes after falling asleep, there is a phase of rapid eye movement, which lasts about 10 minutes. In the phase of REM sleep, during which we see dreams, the data of the electrical activity of the brain are similar to those observed during wakefulness. The muscles of the body are relaxed, which does not allow us to "participate" in our dreams. During this period, cerebral circulation improves.
Why do we need a dream?
For many centuries people have been asking themselves: Why do we need a dream? A healthy sleep is one of the basic human needs. People who for one reason or another have not slept for several days, have symptoms of paranoia, visual and auditory hallucinations. One of the theories designed to prove the need for sleep is based on the fact that sleep helps us conserve energy: the daily metabolism is four times more intense than the nighttime metabolism. Another theory suggests that sleep helps the body recover. For example, in the phase of deep sleep, growth hormone is released, which ensures the renewal of organs and tissues, such as blood, liver, and skin. Sleep also facilitates the function of the immune system. This can explain the increased need for sleep in infectious diseases, such as influenza. Some scientists believe that sleep allows you to "train" the rarely used ways of nervous transmission, connected by synapses (these are small intervals between the nerves through which the nerve impulse passes).
Dreaming
In the world there are only a few cultures that do not attach importance to dreams. Themes of dreams are diverse: from everyday situations to amazing and horrible fantastic stories. It is known that dreams appear in the phase of fast sleep, which lasts for adults in general about 1.5 hours, and in children -8 hours. In this regard, it can be assumed that dreams have a certain effect on the brain, ensuring its growth and the formation of new connections between the brain cells. Modern science allows you to record and analyze the curve of the bioelectric potentials of the brain. In the dream, the brain processes the experience acquired during the waking period, keeps in mind some facts and "erases" the others. It is believed that dreams are a reflection of those facts that are "erased" from our memory. Perhaps, dreams help us in solving problems of everyday life. In one study, just before falling asleep, students were offered a task. Scientists observed the phases of sleep. Parts of the students allowed to sleep without waking, others awakened at the appearance of the first signs of dreaming. It was found that students, awakened during dreams, knew exactly how to solve the task assigned to them.