Electrophysiological Offensive of Sleep in Children
- the disappearance of a-activity on the EEG and its replacement by the low-latency activity of the mixed frequency;
- the appearance of slow movements of eyeballs on the electrooculogram;
- reduction of muscle tone on the electromyogram;
- generalized or local involuntary muscular contractions (electromyogram) - hypnotic myoclonus.
There are two qualitatively different phases of sleep:
- orthodox sleep, the phase of slow sleep (FMS);
- paradoxical sleep, fast sleep phase (FBS), or REM.
It is believed that 3 groups of neurons participate in the regulation of the cyclic phases of sleep.
The aminergic system (serotonergic + noradrenergic), or REM-off cells.
Cholinergic reticular system, or REM-on cells.
Separate phases and stages are best distinguished by their encephalographic characteristics:
- I stage - a nap with the gradual disappearance of a-rhythm;
- II stage - the appearance of a specific for this phase of encephalographic activity - the spindles of sleep, with a slowing of the pulse, decreasing breathing, relaxation of the muscles;
- III and IV stages - stages of deeper sleep, characterized by the appearance of high-amplitude 8-activity, an increase in heart rate.
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Phase of fast sleep in children
The phase of fast sleep is characterized by a fast desynchronized EEG, which is characteristic of intense wakefulness, although the child is in a state of deep sleep. In this stage rapid eye movements, low tone of skeletal muscles and the greatest instability of vegetative functions are noted - arrhythmia of cardiac activity, up to short-term asystole, arrhythmia of respiration, falling of arterial pressure. In the fast sleep phase, active mental activity is also marked - bright dreams experienced.
At all age stages, sleep is organized cyclically, that is, successive stages of slow sleep terminate in a phase of fast sleep. A few full cycles are observed during the night.
The change in the structure and duration of deep sleep can be ascertained by a characteristic such as the number of movements in a dream. The child of the first years of life has more than the older children (80 to 60), but the abundance of movements in a dream does not prevent the younger from sleeping, and often leads to the awakening of the older child.
The phase of fast sleep is characterized by physiological myoclonus - small fast twitching of individual muscle beams and groups with minor movement in small joints, such as twitching of the fingers and facial muscles. In stages of slow sleep, myoclonus is significantly less.
The first period of FBS is noted in 70-100 minutes from the onset of sleep. The EEG picture at this phase resembles that observed in the first stage of FMS, but often it appears waves like the saw's teeth.
The phases of slow and rapid sleep alternate throughout the entire sleep time at intervals of 90-120 minutes. At the age of 2-3 years, the duration of one cycle of sleep is about 60 minutes and the first episode of FBS is observed 1 hour after the child falls asleep. By 4-5 years, the cycle can last up to 90 minutes and during the entire sleep period, about 7 cycles are recorded, which is almost identical to that of an adult.
The phase of slow sleep in the child
The phase of slow sleep acquires significance in the overall structure of sleep after 36 weeks of gestation, but has very little duration. In a newborn child with normal gestation, FBS, FMS and undifferentiated sleep are identified. FBS can be recognized by sucking movements, almost continuous body movements, tremors, grimaces and even elements of walking, irregular breathing, coinciding with flashes of muscle activity. FMS is characterized by minimal motor activity and a higher muscle tone.