The main role in the regulation of body functions and ensuring its integrity belongs to the Central nervous system and its tertiary division - the bark of the big hemispheres. The structure of the nervous system is extremely difficult, and many areas still remain a mystery. But modern science is on the outskirts of the knowledge of the most confidential mysteries of this amazing and probably the only one in the whole universe mechanism. Now science has knowledge of the basic laws nervous activity, which were opened by the works of many brilliant scholars and first of all by the genius of Russian scientists in the XIX-XX centuries - I. M. Sechenov, V. A. Betz, I. P. Pavlov, V. M. Bekhterev, N. That is, Vvedensky and A. A. Ukhtomsky.
Above we noted two most important functions of the nervous system: 1) implementation of communication between all bodies and body parts, consolidation (integration) of all structures of the body in a single integrated system of the body; 2) the communication of the organism with the environment through information, which give us the senses.
Fig. 41. General plan of structure of the nervous system:
1 - the brain;
2 - the spinal cord;
3 - peripheral nervous system.
Look, what are the basic principles of the structure of the nervous system necessary for the administration of these important functions (Fig. 41).
The main structural and work item nervous system is the nerve cell (neuron). Despite the diversity of nerve cells (Fig. 42), the plan of their structure is the same. Each neuron consists of a body and the processes through which the connection between nerve cells themselves and with different authorities. The shape of neurons reflects their core function of communication. The size of cells varies widely: from 5 to 150 m (microns); the number of processes is different, length varies from tenths of mm to 1.5 m, for example, long processes of some sensitive cells lying in the lumbar region, reach the tip of big toe (!).
Essential role in the structure of the nervous system has a special type of connective tissue - glia (Fig. 43). She performs supporting role in the Central nervous system and participates in ensuring the supply of nerve cells.
According to some scientists, the elements glia can participate in carrying out of irritation. Features guess even that cells can participate in the processes that ensure the memory.
Under the influence of chemical or physical impacts nerve cells come in active state, or, as they say, in a state of excitement. The peculiarity of neurons is that they can adopt and pass the initiation of other nerve cells or working bodies (the muscles or glands). The transfer of excitation from one nerve cell to another is carried out in places of their contacts (so-called synapses *). Each neuron has many connections with other nerve cells.
Fig. 42. The form of nerve cells:
Fig. 43. Glia.
Interestingly, in the transmission of nerve impulses in the endings of nerve cells are highlighted chemicals called neurotransmitters. They excite the adjacent squares. As you can see, in the propagation of the nerve process plays the role of a chemical factor. This points to the close link between the processes of nerve and humoral regulation. The formula of the structure of the mediators now well known. For example, the neurotransmitters norepinephrine and acetylcholine are produced our pharmaceutical industry and have wide application in medicine.
All of nervous processes are accompanied by electric phenomena that can be observed and register with the help of special instruments. Electric current occurs as a result of complicated physical and chemical processes taking place in the cytoplasm of nerve cells during their work. Study of the electric currents of the nervous system allows us to judge the nature of its work and is used for diagnostics of nervous and mental diseases.
The nerve cells are specialized. Some of them are used only for transmitting signals from the senses to the brain and spinal cord, these cells are called sensitive. Their long shoots begin senses from nervous special devices, perceiving irritants, called receptors.
* The term "SINAPSE" comes from the Greek word "Kinesis" connection.