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Brain

Год написания книги
2023
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"The human brain represents 1011 connected and interacting neurons. The following main parts are distinguished in the neuron: body, branches and ends. The body of the neuron is an accumulation of cellular plasma (cytoplasm), which houses the nucleus – the carrier of genetic information and mitochondria – universal energy generators needed to support the cell's activity. The surface of the nucleus is covered by a shell, which is called a membrane. The membrane is the structure in which complex bioelectrical processes take place, ensuring the exchange of the nerve cell with the environment.

The brain works continuously, only in different states it functions differently.

When the state of consciousness is changed (sleep, hibernation, trance, hypnosis, meditation, intoxication, hallucination, delirium, madness, trauma, etc.) the brain continues to work and goes to a different level. It is known that the reflection of brain activity is its bioelectric activity or electroencephalogram.

In modern conditions wide application in experimental and clinical-diagnostic practice has received use of a method of electroencephalography (EEG): "As applied to everyday conditions EEG represents simple enough procedure which does not cause any troubles to the investigated person. A standard number of electrodes are applied to the surface of the head with the help of which potentials from the corresponding areas of the projection of the cortex are recorded and after the preliminary amplification they are recorded in one way or another – on paper, film, tape recorder. Potentials recorded in this way have a value from very weak to 150-

200 мV in a very wide range of frequencies. For the analysis the following frequencies (rhythms) are used more often than others: delta rhythm – 2-4 col/sec, theta rhythm – 4-8, alpha rhythm – 8-13, beta rhythms – 13-30 col/sec. Other indicators are also used in special conditions. The nature of EEG-activity reflects the interaction of different parts of the brain, but expressed in the activity of the cortex of large hemispheres, in the interaction and dynamics of excitation and inhibition processes on its surface.

"At low brain activity, large groups of nerve cells discharge simultaneously, and this synchrony is displayed in the EEG as low frequency waves and large amplitude as "slow waves": 1) alpha waves with frequencies ranging from 8 to 12 cycles per second (8-12 Hz), they are characteristic of a relaxed body when a person sits comfortably with the Gauls closed; 2) theta waves with frequencies ranging from 4 to 7 Hz, they appear in the first stage of sleep; 3) delta waves (0.5-3 Hz), which are recorded during deep sleep. During brain activity, each participating nerve cell discharges with its own specific function in its own rhythm; as a result, brain activity becomes asynchronous and is recorded as fast waves of high frequency and small amplitude – "beta waves" (13-26 Hz); the amplitude of beta waves decreases as brain activity increases. Beta waves are recorded during waking, active mental and physical activity, and, oddly enough, during "fast sleep".


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