touch

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Related to somatosensory system: fascia, somatosensory cortex

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.

Touch

 

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.

REFERENCES

Granit, 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


Touch

 

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

[təch]
(physiology)
The array of sensations arising from pressure sensitivity of the skin.

touch

1. Rugby Soccer the area outside the touchlines, beyond which the ball is out of play (esp in the phrase in touch)
2. Archaic
a. an official stamp on metal indicating standard purity
b. the die stamp used to apply this mark
3. a scoring hit in competitive fencing
4. an estimate of the amount of gold in an alloy as obtained by use of a touchstone
5. the technique of fingering a keyboard instrument
6. the quality of the action of a keyboard instrument with regard to the relative ease with which the keys may be depressed
7. Bell-ringing any series of changes where the permutations are fewer in number than for a peal

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.
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In light of these concerns, a physical therapy team must encourage patients with DN to compensate by using the somatosensory system and ankle proprioception [4].
These sensory systems include the olfactory system, which detects odours, and the somatosensory system, responsible for detecting irritants, chemicals that cause pain, tingling, burning, stinging, or prickling.
These effects of facial skin stretch indicate the involvement of the somatosensory system in the neural processing of speech sounds.
One potentially promising method for assessing the mechanisms that contribute to the development and/or maintenance of neuropathic pain after SCI is the use of quantitative sensory testing (QST) to evaluate the hypoand hypersensitivity of the somatosensory system [11].
suggested that the following criteria be fulfilled: (1) a neuroanatomically plausible pain distribution, (2) a history of a relevant lesion or disease affecting the peripheral or central somatosensory system, (3) negative or positive sensory signs within the body area corresponding somatotopically to central nervous system injury or peripheral nerve or root, and (4) a diagnostic test confirming a lesion or disease involving central or peripheral nervous structures relevant for the presence of neuropathic pain.

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