When we touch objects of different forms and surfaces, the brain receives more exact signals, than that go to it from organs of vision, hearing, sense of smell and taste.
The Person possesses five feelings. This sight, taste, hearing, sense of smell and touch. It is the most difficult to define and understand touch mechanisms: after all, as a matter of fact, it is the whole complex of different sensations. Besides, touch as if podstrahovyvaet other feelings also certifies that before us actually about what they have told to us.
a touch Role
Unlike other four feelings which are realised through concrete bodies - eyes, ears, a nose or a mouth, - osjazatelnye sensations are perceived on all body. If other feelings react only to one kind of irritation, osjazatelnaja the system is sensitive both to temperature, and to a pain. Probably, it is the most easier to imagine touch as a set of different feelings; some of them have the special nervous terminations in our skin, muscles and in other places; there they respond to the most various irritations and transfer the received impressions in a brain in turn processing these information signals.
As we perceive?
Touch allows the person to learn and make much. Thanks to touch you will feel someone's touch or blow; thanks to it you can, without considering, to define the size and the form of any subject, to learn, how much it is heavy, firm it or is soft, hot or cold.
The Sensation of temperature or a pain prompts to a brain that the body is threatened with danger before there is a comprehension of this danger, and the organism immediately will react to it to be protected. For example, you will draw aside a hand from a hot surface before she will have time to burn you.
To learn about work of organs of touch, scientists needed a lot of time and efforts. When for the first time it became known that the tactile sense depends on the signals perceived by several various kinds of the nervous terminations, researchers have assumed that each nervous termination reacts only to one concrete razdrazhitel, a pain, pressing, a cold or heat.
However, it is fast supporters of this theory have encountered difficulties. Though some nervous terminations are especially sensitive only to one razdrazhitelju, others not only react to different irritations, but also a little than differ from each other. Further it was found out that sensations distinguished by the nervous terminations make only small share of all accessible and received sensations. During the further researches it became clear that each nervous termination has the retseptivnoe a field - that site of a skin which at irritation causes activity of a corresponding nerve. Thus retseptivnye fields are imposed against each other and if to press on a concrete point on a skin surface, some nerves will come to an excitation condition at once. Besides it, everyone concrete osjazatelnyj the nerve can come to a condition of activity both under the influence of other force of pressing, and under the influence of temperature changes in limits retseptivnogo fields.
Posylanie of signals
Nervous fibres of the person continuously react to set razdrazhitelej, but only those from them that bear a signal about temperature and pressure, are strong enough for recognition by a brain. Both the temperature, and pressure cause considerable activity in nervous fibres, and generated signals with the increased speed are transferred in the central nervous system. Speed from which the signal arrives in a brain, speaks to a brain about what type razdrazhitel operates at present. The osjazatelnyj signal goes from final bodies through nervous fibres on somatic nerves to the central nervous system.
Various retseptivnye fields differ on degree of sensitivity which depends on concentration of the nervous terminations in various sites of a human skin. For example, everyone can feel that to it on a language tip press two sharply perfected pencil slate pencils even if they will be in 1 mm from each other; and if to prick them in the field of a back only in case of distance in 5 sm between them the person will feel not one external razdrazhitel, and a little.
Thus that separate kinds of the nervous terminations are more sensitive to some kinds of external irritation, the majority of experts has come to a conclusion that the combination of the signals distinguished by a brain as certain sensation, is defined by speed of distribution of signals and their distribution on small and big nervous fibres.
As touch gives us so many knowledge of world around, it can replace a lack of other sensations. The best example - the font of Brajlja allowing visually impaired to read by means of fingers.