Mechanoreceptors can detect pressure at inside or outside body surfaces {touch, sense}. Compression, tension, and torsion stresses cause body-surface strains. Touch analyzes material properties, such as temperature, texture, surface curvature, density, hardness, and elasticity. Touch is a synthetic sense, with some analysis. Protozoa have touch and stretch receptors.
physical properties
Touch events include tissue stresses, motions, and vibrations, which displace surfaces and regions. Stresses vary in area, pressure, and vibration states. Pressures include compression, tension, and torsion. Stresses and stress changes stress skin mechanical receptors.
types
People can feel "butterflies", tickle, tingle, gentle touch, regular pressure, and sharp pressure. People can feel motion and vibrations up to 20 Hz. People can feel object temperature, texture, surface curvature, density, hardness, and elasticity.
Touches relate in only one consistent and complete way. Touches are not symmetric, so touches have unique relations. Touches cannot substitute. Touches have specific sense qualities and so can never switch to other touches. Touches do not have opposites. Touch has same physical properties, and touch processes are similar, so touch perceptions are similar, for all undamaged people.
Touch is pleasurable for babies and parents and for sexual relations. Perhaps, the first touch was for food or mating.
properties
Touch habituates quickly. Touch is in real time, with a half-second delay. Touch can detect low pressure or speed. Touch is painful at high pressure or speed. Touches do not mix to make new touches. Age reduces vibration sensitivity.
source location
Touch can locate body and objects {where system}.
From one location, touch detects only one source.
Touch can detect multiple sensations simultaneously.
Touch has no fixed coordinate origin (egocenter), so coordinates change with task.
evolution
Humans have higher touch sensitivity than other mammals. Lower animals have even less touch sensitivity. Perhaps, the first touch was for food or mating.
Protozoa have touch and stretch receptors.
development
Newborns can turn in touched-cheek direction.
effects
Pressure and touch receptor activity increases muscle flexor activity and decreases muscle extensor activity.
Emotions generate brain-gut hormones that cause abdominal feelings.
relations to other senses
Hearing, temperature, and touch involve mechanical energy.
Touch can feel vibrations below 20 Hz. Sound vibrates eardrum and other body surfaces but is not felt as touch. Touch uses higher energy level than hearing. Hearing uses waves that travel far, but touch uses vibrations that travel short. Hearing and touch have no input from most spatial locations. Hearing has sound attack and decay, and touch has temporal properties.
Touch can feel air near smell receptors and react to noxious smells. Touch locates smell receptors in upper nose.
Touch can feel solutions on tongue and react to noxious tastes. Touch locates tongue taste receptors.
Touch coordinates with vision.
Nociceptive and thermal receptor systems interact. Tactile and thermal receptor systems interact.
People can have extreme touch sensitivity and low pain threshold {hyperaesthesia, touch}|.
Sense-nerve myelinated-fiber pathways {epicritic pathway} {lemniscal system} can begin at Meissner's corpuscles, Pacinian corpuscles, hair root structures, muscle spindles, and Golgi tendon organs, go through lateral cervical nucleus, continue to gracile and cuneate nuclei, and end at cerebellum and thalamus.
Skin mechanical receptors send to spinal cord, brainstem nuclei, thalamus, and parietal lobe.
Skin mechanoreceptor fibers {A-beta fiber} can be large.
Meissner corpuscles are fast-adapting mechanoreceptors and have small receptive fields {fast-adapting fiber I} (FA I).
Pacinian corpuscles are fast-adapting mechanoreceptors and have large receptive fields {fast-adapting fiber II} (FA II).
Merkel receptors are slow-adapting mechanoreceptors and have small receptive fields {slow-adapting fiber I} (SA I).
Ruffini receptors are slow-adapting mechanoreceptors and have large receptive fields {slow-adapting fiber II} (SA II).
Skin, muscles, tendons, joints, alimentary canal, and bladder have mechanical receptors that detect tissue strains, pressures/stresses (compression, tension, and torsion), motions, and vibrations {touch receptor}. Eight basic mechanoreceptor types each have many variations, making thousands of combinations. Skin has encapsulated tactile receptors, free-nerve-ending receptors, hair-follicle receptors, Meissner's corpuscles, Merkel cells, Pacinian corpuscles, palisade cells, and Ruffini endorgans.
Skin mechanoreceptors (thermoreceptor) can detect surface temperature. Muscles, tendons, joints, alimentary canal, and bladder have thermoreceptors. Skin mechanoreceptors (cold fiber) can detect decreased skin temperature. Cold receptors are mostly on face and genitals. Skin has receptors (warmth fiber) that detect increased skin temperature. Heat receptors are deep in skin, especially in tongue. Warm fibers are 30 times fewer than cool fibers.
Skin mechanoreceptors {free nerve ending} respond to all skin-stimulation types, because they are specialized receptors.
Skin mechanoreceptors {hair cell, skin}, with tip cilia {stereocilia} {stereocilium}, detect movement. Stereocilia movement begins neurotransmitter release. Hair cells send to brainstem and receive from brain.
Woodpeckers have tongue vibration detectors {Herbst corpuscle}, which are like Pacinian corpuscles.
Skin encapsulated mechanoreceptors {Krause end bulb} {Krause's end bulb} are in mammals other than primates and correspond to primate Meissner's corpuscles. Krause end bulbs are mostly in genitals, tongue, and lips.
Teleosts have side canals and openings {lateral line system}|, running from head to tail, which perceive water pressure and flow changes. Visual signals influence lateral-line perceptions.
Primate glabrous-skin encapsulated mechanoreceptors {Meissner's corpuscle} {Meissner corpuscle} are fast-adapting, have small receptive fields of 100 to 300 micrometers diameter, and lie in rows just below fingertip surface-ridge dermal papillae. Meissner's corpuscles are only in primates and correspond to Krause end bulbs in other mammals.
Meissner's corpuscles respond to vibration, to detect changing stimuli. Maximum sensitivity is at 20 to 40 Hz. Range is from 1 Hz to 400 Hz. Meissner's corpuscles send to myelinated dorsal-root neuron fibers.
Numerous encapsulated mechanoreceptors {Merkel cell} {Merkel-cell neurite complex} form domes {Iggo-Pinkus dome} visible at skin surfaces. Merkel cells are slow-adapting, have small receptive fields of 100 to 300 micrometers diameter, and are in hairy-skin epidermis-bottom small scattered clusters and in glabrous-skin epidermis rete pegs.
Merkel cells detect continuous pressures and deformations as small as one micrometer. Merkel cells detect 0.4-Hz to 3-Hz low-frequency vibrations. Merkel cells send to myelinated dorsal-root neuron fibers.
Enzymes {ODC enzyme} begin touch chemical changes.
Encapsulated mechanoreceptors {pacinian corpuscle}, 1 to 2 mm diameter, detect deep pressure. Pacinian corpuscles are fast-adapting, have large receptive fields, and are in body, joint, genital, and mammary-gland hairy-skin and glabrous-skin deep layers.
Pacinian corpuscles respond to vibration with maximum sensitivity at 200 to 300 Hz. Range is 20 to 1500 Hz. Pacinian corpuscles can detect movements smaller than one micrometer. Pacinian corpuscles have lamellae, which act as high-pass filters to prevent steadily maintained pressure from making signals. Pacinian corpuscles send to myelinated dorsal-root neuron fibers.
Hair follicles have pressure mechanoreceptors {palisade cell, touch} {hair follicle nerve}, around hair-shaft base, that have three myelinated-fiber types. Palisade cells respond to different deformations. Palisade cells respond to vibration frequencies from 1 to 1500 Hz.
Encapsulated skin mechanoreceptors {Ruffini's endorgan} {Ruffini endorgan} {Ruffini ending} are spindle shaped and 1 mm to 2 mm long, similar to Golgi tendon organs. Ruffini's endorgans are slow-adapting, are in joints and glabrous-skin dermis, and have large receptive fields (SA II), several centimeters diameter in arms and trunk. Ruffini endorgans have densely-branched center nerve endings.
Ruffini endorgans respond to skin slip, stretch, and deformation, with sensitivity less than that of SA I receptors. Ruffini endorgans respond to 100 Hz to 500 Hz. Ruffini endorgans send to myelinated dorsal-root neuron fibers.
Skin has hair-follicle receptors, Meissner's corpuscles, Merkel cells, Pacinian corpuscles, and Ruffini endorgans {skin receptor}.
Skin encapsulated mechanoreceptors {tactile receptor} are for vibration, steady pressure, and light touch. Receptors measure amplitude, constancies, changes, and frequencies.
Mechanoreceptors detect pressures, strains, and movements {touch, physiology}. Touch stimuli affect many touch-receptor types, which excite and inhibit each other to form intensity ratios. Receptors do not make equal contributions but have weights. Receptor sensitivity varies over touch spectrum and touch region [Katz, 1925] [McComas and Cupido, 1999] [Teuber et al., 1960] [Teuber, 1960].
Touch is more about weight, heat transfer, texture, and hardness {material property, touch} than about shape {geometric property, touch}. Weight discrimination is best if lifted-weight density is one gram per cubic centimeter. Touch receptors can detect mechanical vibrations up to 20 to 30 Hz.
Touch can detect body location. From one location, touch detects only one source. Touch can detect multiple sensations simultaneously. Touch has no fixed coordinate origin (egocenter), so coordinates change with task.
Pressure, pain, and touch receptor activity increases muscle flexor activity and decrease muscle extensor activity.
Mechanoreceptors detect pressures/stresses (compression, tension, torsion), strains, motions, and vibrations [Bolanowski et al., 1998] [Hollins, 2002] [Johnson, 2002]:
Free nerve ending: smooth or rough surface texture
Hair cell: motion
Meissner corpuscle: vibration
Merkel cell: light compression and vibration
Pacinian corpuscle: deep compression and vibration
Palisade cell: light compression
Ruffini endorgan: slip, stretch, and vibratio
pressure
Skin encapsulated tactile receptors are for steady pressure and light touch.
Skin free-nerve-ending mechanoreceptors respond to all skin-stimulation types.
Merkel cells detect continuous pressures and deformations as small as one micrometer. Merkel cells detect 0.4-Hz to 3-Hz low-frequency vibrations. Merkel cells are slow-adapting.
Pacinian corpuscles detect deep pressure. Pacinian corpuscles are fast-adapting.
Palisade cells respond to different deformations.
Ruffini endorgans respond to skin slip, stretch, and deformation, with sensitivity less than that of SA I receptors. Ruffini's endorgans are slow-adapting.
Nerve signals differ for pain, itch, heat, and pressure [Bialek et al., 1991]. Pain is irregular and high intensity and has rapid increase. Itch is regular and fast. Heat rises higher. Pressure has high intensity that fades away.
People can distinguish 10 stress levels. Maximum touch is when high pressure causes tissues to have inelastic strain, which stretches surface tissues past point to which they can completely return and which typically causes pain.
vibration
Skin encapsulated tactile receptors are for vibration.
Skin free-nerve-ending mechanoreceptors respond to all skin-stimulation types.
Meissner's corpuscles respond to vibration, to detect changing stimuli. Maximum sensitivity is at 20 to 40 Hz. Range is from 1 Hz to 400 Hz. Meissner corpuscles are fast-adapting.
Pacinian corpuscles respond to vibration with maximum sensitivity at 200 to 300 Hz. Range is 20 to 1500 Hz. Pacinian corpuscles can detect movements smaller than one micrometer. Pacinian-corpuscle lamellae act as high-pass filters to prevent steadily maintained pressure from making signals. Pacinian corpuscles are fast-adapting.
Palisade cells respond to vibration frequencies from 1 to 1500 Hz.
Ruffini endorgans respond to 100 Hz to 500 Hz. Ruffini's endorgans are slow-adapting.
People can distinguish 10 vibration levels. Age reduces vibration sensitivity.
movement
Skin hair-cell mechanoreceptors detect movement.
Skin free-nerve-ending mechanoreceptors respond to all skin-stimulation types.
The touch system can detect whether objects are stationary. Touch can tell whether surface is sliding under stationary skin, or skin is sliding over stationary surface.
Most objects connect to the ground and are stationary. Their connection to the ground makes them have high inertia and no acceleration when pushed or pulled.
Objects that slide past stationary skin have inertia similar to or less than the body. (If large object slides by skin, the collision affects the whole body, not just the skin.) They have measurable deceleration when pushed or pulled.
The touch system measures accelerations and decelerations in the skin. Large decelerations in skin result from sliding by stationary objects. Small decelerations in skin result from objects sliding by skin.
People can distinguish 10 motion levels.
space
Skin touches objects, and touch receptors receive information about objects adjacent to body. As body moves around in space, mental space expands by adding adjacency information. Sensations impinge on body surface in repeated patterns at touch receptors. From receptor activity patterns, nervous system builds a three-dimensional sensory surface.
Foot motions stop at ground. Touch and kinesthetic receptors define a horizontal plane in space.
People can distinguish inside-body stimuli, as self. Tightening muscles actively compresses, to affect proprioception receptors that define body points. When people move, other objects do not move, so correlated body movements belong to self.
People can distinguish outside-body stimuli, as non-self. During movements or under pressure, body surfaces passively extend, to affect touch receptors that define external-space points. When people move, correlated non-movements belong to non-self.
Because distance equals rate times time, motion provides information about distances. Nervous system correlates body motions and touch and kinesthetic receptors to extract reference points and three-dimensional space. Repeated body movements define perception metrics. Such ratios build standard length, angle, time, and mass units that model physical-space lengths, angles, times, and masses. As body, head, and eyes move, they trace geometric structures and motions.
material properties
Touch can identify {what system}.
Holding in hand determines weight.
Touching with no moving determines temperature. Material properties determine heat flow, which determines temperature, which ranges from cold to warm to pain. Temperature perceptual processes compare thermoreceptor inputs. People can distinguish 10 temperature levels.
Applying pressure determines hardness.
Sliding touch back and forth determines texture.
Wrapping around determines shape and volume. Following contours determines shape.
Touch is more about weight, heat transfer, texture, and hardness than about shape. Weight discrimination is best if lifted-weight density is one gram per cubic centimeter.
qualities
Emotions generate brain-gut hormones that cause abdominal feelings. Maximum touch is when high pressure causes tissues to have inelastic strain, which stretches surface tissues past point to which they can completely return and which typically causes pain.
neuron
Nerve signals differ for pain, itch, heat, and pressure [Bialek et al., 1991]. Pain is irregular and high intensity and has rapid increase. Itch is regular and fast. Heat rises higher. Pressure has high intensity that fades away.
EEG
In NREM sleep, anesthesia, and waking, short touch causes P1 cortical response 25 milliseconds later. In waking, short touch causes N1 cortical response 100 milliseconds later, lasting hundreds of milliseconds.
temperature
Coolness and warmth are relative and depend on body-tissue relative average random molecule speed. Very cold objects can feel hot at first. Skin is normally 30 C to 36 C. If objects are colder than 30 C, cold fibers provide information about material as heat flows from skin to object. If skin is above normal temperature, warmth fibers provide information about material as heat flows from skin to object. Warmth fibers also provide information about body state, such as fever or warm-weather overheating.
When touching objects, people use hand-movement patterns {exploratory procedure} to learn about features. Applying pressure determines hardness. Wrapping around determines shape and volume. Following contours determines shape. Touching with no moving determines temperature. Sliding touch back and forth determines texture. Holding in hand determines weight.
Skin, muscles, tendons, and joints have mechanoreceptors that work with muscle movements to explore environment. Touching by active exploration with fingers {haptic touch} {haptic perception} uses one information channel. Passive touch uses parallel channels. Touch can tell whether surface is sliding under stationary skin, or skin is sliding over stationary surface. See Figure 1.
At different skin areas, for people to perceive separate touches, two touches must be separate by greater or smaller distances {two-point threshold}.
Touch can identify {what system, touch}. Touch is more about weight, heat transfer, texture, and hardness than about shape.
Touch can locate {where system, touch}.
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Date Modified: 2022.0225