Difference between revisions of "Touch" - New World Encyclopedia
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| − | + | '''Touch''' (or '''tangoreception''') is the physiological sense by which animals perceive an object in their environment when it comes into contact with the body surface. It belongs to a variety of closely connected mechanisms or faculties (collectively known as ''the [[sense]]s'') by which a living organism receives information about its external or internal environment. | |
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| + | There are two main types of sensory receptors related to touch: ''tactile hairs'' and ''subcutaneous receptors'' (receptors below the skin’s surface). Many animals, ranging from insects and other anthropods to birds and mammals, have hairs or hairlike projections richly supplied with nerves. Some hairs, such as [[whisker]]s, may be specially modified in certain areas of the body to provide more sensitive discrimination among sensory stimuli. | ||
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| + | Sensory receptors below the skin are a second means of perceiving touch, which is a type of ''mechanoreception'', or sensitivity to mechanical stimuli. Like other sensory cells, mechanosensors associated with touch convert physical stimuli into signals that are transmitted to specific areas of the [[central nervous system]] (i.e., the spinal cord and brain) for processing and interpretation. Stimuli create a temporary physical distortion in the membranes of these specialized receptors, causing ion channels to open and altering the resting potential of the cell, which in turn leads to the generation of [[action potential]]s, the message system of the nervous system. Density of tactile sensors varies across the body, but tends to be particularly concentrated in hairless skin like lips and fingertips. | ||
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| + | section on Braille example – exteroreception; The sense of touch is very closely related to the other four sensations received by the skin: pain, pressure, heat, and cold. It often combines with other senses to give the organism complex feedback about the external environment (exteroreception). Other features of the animal work in conjunction with touch receptors to enhance ability, like getting information about spatial position proprioreception) – i.e., external feedback helps the organism to understand its own positionality | ||
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| + | how interconnected the skin’s sense perceptions are, why it’s difficult to divorce touch from other senses | ||
==Anatomy== | ==Anatomy== | ||
| − | + | objects touching our skin generate diverse sensations because our skin is packed with a variety of mechanosensors: | |
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| + | the outer layers of skin, esp hairless skin like lips and fingertips, contain whorls of nerve endings enclosed in connective-tissue capsules: they are Meissner’s corpuscles – respond to objects that touch the skin even lightly | ||
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| + | expanded-tip tactile sensors also located in outer regions; differ from M’s corpuscles in that they adapt only partly and slowly; useful for providing steady-state information about objects that continue to touch the skin | ||
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| + | density of tactile sensors varies across the surface of the body | ||
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| + | Pacinian corpuscle senses pressure (deep in skin; made up of concentric layers of connective tissue that encapsulate an extension of a sensory neuron); respond esp well to vibrations applied to the skin, but adapt rapidly to steady pressure | ||
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| + | Krause’s end bulb senses touch; Ruffini’s corpuscle senses touch and pressure | ||
==How touch works== | ==How touch works== | ||
Revision as of 20:05, 20 October 2007
Touch (or tangoreception) is the physiological sense by which animals perceive an object in their environment when it comes into contact with the body surface. It belongs to a variety of closely connected mechanisms or faculties (collectively known as the senses) by which a living organism receives information about its external or internal environment.
There are two main types of sensory receptors related to touch: tactile hairs and subcutaneous receptors (receptors below the skin’s surface). Many animals, ranging from insects and other anthropods to birds and mammals, have hairs or hairlike projections richly supplied with nerves. Some hairs, such as whiskers, may be specially modified in certain areas of the body to provide more sensitive discrimination among sensory stimuli.
Sensory receptors below the skin are a second means of perceiving touch, which is a type of mechanoreception, or sensitivity to mechanical stimuli. Like other sensory cells, mechanosensors associated with touch convert physical stimuli into signals that are transmitted to specific areas of the central nervous system (i.e., the spinal cord and brain) for processing and interpretation. Stimuli create a temporary physical distortion in the membranes of these specialized receptors, causing ion channels to open and altering the resting potential of the cell, which in turn leads to the generation of action potentials, the message system of the nervous system. Density of tactile sensors varies across the body, but tends to be particularly concentrated in hairless skin like lips and fingertips.
section on Braille example – exteroreception; The sense of touch is very closely related to the other four sensations received by the skin: pain, pressure, heat, and cold. It often combines with other senses to give the organism complex feedback about the external environment (exteroreception). Other features of the animal work in conjunction with touch receptors to enhance ability, like getting information about spatial position proprioreception) – i.e., external feedback helps the organism to understand its own positionality
how interconnected the skin’s sense perceptions are, why it’s difficult to divorce touch from other senses
Anatomy
objects touching our skin generate diverse sensations because our skin is packed with a variety of mechanosensors:
the outer layers of skin, esp hairless skin like lips and fingertips, contain whorls of nerve endings enclosed in connective-tissue capsules: they are Meissner’s corpuscles – respond to objects that touch the skin even lightly
expanded-tip tactile sensors also located in outer regions; differ from M’s corpuscles in that they adapt only partly and slowly; useful for providing steady-state information about objects that continue to touch the skin
density of tactile sensors varies across the surface of the body
Pacinian corpuscle senses pressure (deep in skin; made up of concentric layers of connective tissue that encapsulate an extension of a sensory neuron); respond esp well to vibrations applied to the skin, but adapt rapidly to steady pressure
Krause’s end bulb senses touch; Ruffini’s corpuscle senses touch and pressure
How touch works
mechanoreception stuff
Function
usual stuff plus something on haptic technology
ReferencesISBN links support NWE through referral fees
- Flanagan, J.R., Lederman, S.J. Neurobiology: Feeling bumps and holes, News and Views, Nature, 2001 Jul. 26;412(6845):389-91.
- Hayward V, Astley OR, Cruz-Hernandez M, Grant D, Robles-De-La-Torre G. Haptic interfaces and devices. Sensor Review 24(1), pp. 16-29 (2004).
- Purves to add
- Robles-De-La-Torre G., Hayward V. Force Can OvercomFLARGUSe Object Geometry In the perception of Shape Through Active Touch. Nature 412 (6845):445-8 (2001).
- Robles-De-La-Torre G. The Importance of the Sense of Touch in Virtual and Real Environments. IEEE Multimedia 13(3), Special issue on Haptic User Interfaces for Multimedia Systems, pp. 24-30 (2006).
External links
| Nervous system: Sensory systems/sense | |
|---|---|
| Special senses | Visual system/Visual perception • Auditory system/Hearing • Olfactory system/Olfaction • Gustatory system/Taste |
| Somatosensory system | Nociception • Thermoreception • Vestibular system • Mechanoreception (Pressure, Vibration, Proprioception) |
| Other | Sensory receptor |
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