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.
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Date Modified: 2022.0225