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touch,tactile sensation received by the skin, enabling the organism to detect objects or substances in contact with the body. End organs (nerve endings) in the skin convey the impression to the brain. Touch sensitivity varies in different parts of the body, depending on the number of end organs present in any one area. The tip of the tongue, lips, and fingertips are three of the most sensitive areas, the back and parts of the limbs the least so. The sense of touch is very closely related to the other four sensations received by the skin: pain, pressure, heat, and cold. There is a specific kind of sensory receptor for each of the five so-called cutaneous senses. For example, light-touch receptors convey only the sensation that an object is in contact with the body, while pressure receptors convey the force, or degree, of contact. The blind learn to read by the Braille system by making use of the sensitivity to touch of the fingertips.
the ability of animals and man to sense environmental factors by means of receptors in the skin; in the locomotor system, which includes the muscles, tendons, and joints; and in some mucous membranes, such as those on the lips and tongue.
The tactile process is based on stimulation of various types of receptors: mechanoreceptors that perceive contact, pressure, and tension; thermoreceptors that perceive heat and cold; and pain receptors. This information then reaches and is transformed by the central nervous system, including the cerebral cortex. The sensation of touch can be quite varied because it results from a complex perception of different properties of a stimulus acting on the skin and subcutaneous tissues. The perception of environmental objects by touch permits evaluations to be made concerning their shape, size, surface properties, consistency, temperature, dryness or wetness, and position and movement in space. At the cellular level, touch breaks down into several different receptor processes: there is no single morphological type of tactile cell.
The sense of touch greatly broadens the organism’s impressions of its surroundings and plays an important role in its vital activity. In many lower animals the sense of touch, together with chemical sensitivity, is the principal means of perceiving the environment. To some extent, touch substitutes for the sensory organs of sight and hearing when they are injured. Touch permits blind persons to read, perform a variety of delicate manual operations, and orient themselves in space. In persons who are both blind and deaf, touch is the main source of information about the outside world and can be developed to an exceptionally high degree. The term “touch” is becoming less common because of increasing knowledge of the receptor processes’ cellular mechanisms; the mechanisms of mechanoreception, thermoreception, and pain are usually considered independently.
REFERENCESGranit, R. Elektrofiziologicheskoe issledovanie retseptsii. Moscow, 1957. (Translated from English.)
Esakov, A. I., and T. M. Dmitrieva. Neirofiziologicheskie osnovy taktil’nogo vospriiatiia. Moscow, 1971.
Fiziologiia sensornykh sistem, part 2. (Ruko-vodstvopo fiziologii.) Leningrad, 1972.
Milner, P. Fiziologicheskaia psikhologiia. Moscow, 1973. Chapters 8, 10. (Translated from English.)
O. B. IL’INSKII
a performer’s particular manner of producing sound on the piano through various ways of pressing and striking the keys. Each pianist has his own individual touch, which depends on his physiology and artistic intent. J. Field and S. Thalberg produced a soft, “velvety” tone; S. V. Rachmaninoff and A. G. Rubinstein played with a deep, rich tone; and K. N. Igumnov elicited a tender, lyric sound.
touch(1) A generic reference to touchscreen interfaces, which means using the finger to tap icons and move objects on a touch-sensitive screen. See touchscreen.
(2) See iPod touch.