Pacinian corpuscle or lamellar corpuscle or Vater-Pacini corpuscle; is one of the four major types of

mechanoreceptors A mechanoreceptor, also called mechanoceptor, is a sensory receptor that responds to mechanical pressure or distortion. Mechanoreceptors are innervated by sensory neurons that convert mechanical pressure into electrical signals that, in animals, a ...

(specialized

nerve A nerve is an enclosed, cable-like bundle of nerve fibers (called axons) in the peripheral nervous system. A nerve transmits electrical impulses. It is the basic unit of the peripheral nervous system. A nerve provides a common pathway for the e ...

ending with adventitious tissue for mechanical sensation) found in mammalian

skin Skin is the layer of usually soft, flexible outer tissue covering the body of a vertebrate animal, with three main functions: protection, regulation, and sensation. Other cuticle, animal coverings, such as the arthropod exoskeleton, have diffe ...

. This type of mechanoreceptor is found in both glabrous (hairless) and hirsute (hairy) skins, viscera, joints and attached to periosteum of bone, primarily responsible for sensitivity to

vibration Vibration is a mechanical phenomenon whereby oscillations occur about an equilibrium point. The word comes from Latin ''vibrationem'' ("shaking, brandishing"). The oscillations may be periodic function, periodic, such as the motion of a pendulum ...

. Few of them are also sensitive to quasi-static or low frequency

pressure Pressure (symbol: ''p'' or ''P'') is the force applied perpendicular to the surface of an object per unit area over which that force is distributed. Gauge pressure (also spelled ''gage'' pressure)The preferred spelling varies by country and e ...

stimulus. Most of them respond only to sudden disturbances and are especially sensitive to vibration of few hundreds of Hz. The vibrational role may be used for detecting surface texture, e.g., rough vs. smooth. Most of the Pacinian corpuscles act as rapidly adapting mechanoreceptors. Groups of corpuscles respond to pressure changes, e.g. on grasping or releasing an object.

Structure

Pacinian corpuscles are larger and fewer in number than Meissner's corpuscle,

Merkel cell Merkel cells, also known as Merkel-Ranvier cells or tactile epithelial cells, are oval-shaped mechanoreceptors essential for light touch sensation and found in the skin of vertebrates. They are abundant in highly sensitive skin like that of the f ...

s and Ruffini's corpuscles. The Pacinian corpuscle is approximately oval-cylindrical-shaped and 1 mm in length. The entire corpuscle is wrapped by a layer of

connective tissue Connective tissue is one of the four primary types of animal tissue, along with epithelial tissue, muscle tissue, and nervous tissue. It develops from the mesenchyme derived from the mesoderm the middle embryonic germ layer. Connective tiss ...

. Its capsule consists of 20 to 60 concentric lamellae (hence the alternative ''lamellar corpuscle'') including fibroblasts and fibrous connective tissue (mainly

Type IV Type may refer to: Science and technology Computing * Typing, producing text via a keyboard, typewriter, etc. * Data type, collection of values used for computations. * File type * TYPE (DOS command), a command to display contents of a file. * T ...

and Type II collagen network), separated by gelatinous material, more than 92% of which is water.

Function

Pacinian corpuscles are rapidly adapting ( phasic) receptors that detect gross pressure changes and vibrations in the

. Any deformation in the corpuscle causes

action potential An action potential occurs when the membrane potential of a specific cell location rapidly rises and falls. This depolarization then causes adjacent locations to similarly depolarize. Action potentials occur in several types of animal cells, ...

s to be generated by opening pressure-sensitive sodium ion channels in the

axon An axon (from Greek ἄξων ''áxōn'', axis), or nerve fiber (or nerve fibre: see spelling differences), is a long, slender projection of a nerve cell, or neuron, in vertebrates, that typically conducts electrical impulses known as action po ...

membrane. This allows sodium ions to flow into the cell, creating a

receptor potential A receptor potential, also known as a generator potential, a type of graded potential, is the transmembrane potential difference produced by activation of a sensory receptor. A receptor potential is often produced by sensory transduction. It is gen ...

. These corpuscles are especially sensitive to vibrations, which they can sense even centimeters away. Their optimal sensitivity is 250 Hz, and this is the frequency range generated upon fingertips by textures made of features smaller than 1 µm. Pacinian corpuscles respond when the skin is rapidly indented but not when the pressure is steady, due to the layers of connective tissue that cover the nerve ending. It is thought that they respond to high-velocity changes in joint position. They have also been implicated in detecting the location of touch sensations on handheld tools. Pacinian corpuscles have a large

receptive field The receptive field, or sensory space, is a delimited medium where some physiological stimuli can evoke a sensory neuronal response in specific organisms. Complexity of the receptive field ranges from the unidimensional chemical structure of od ...

on the skin's surface with an especially sensitive center.

Mechanism

Pacinian corpuscles sense stimuli due to the deformation of their lamellae, which press on the membrane of the

sensory neuron Sensory neurons, also known as afferent neurons, are neurons in the nervous system, that convert a specific type of stimulus, via their receptors, into action potentials or graded potentials. This process is called sensory transduction. The cell ...

and causes it to bend or stretch. When the lamellae are deformed, due to either pressure or release of pressure, a generator potential is created as it physically deforms the plasma membrane of the receptive area of the neuron, making it "leak" Na+ ions. If this potential reaches a certain threshold, nerve impulses or action potentials are formed by pressure-sensitive sodium channels at the first

node of Ranvier In neuroscience and anatomy, nodes of Ranvier ( ), also known as myelin-sheath gaps, occur along a myelinated axon where the axolemma is exposed to the extracellular space. Nodes of Ranvier are uninsulated and highly enriched in ion channels, al ...

, the first node of the

myelin Myelin is a lipid-rich material that surrounds nerve cell axons (the nervous system's "wires") to insulate them and increase the rate at which electrical impulses (called action potentials) are passed along the axon. The myelinated axon can be ...

ated section of the neurite inside the capsule. This impulse is now transferred along the axon with the use of sodium channels and sodium/potassium pumps in the axon membrane. Once the receptive area of the neurite is depolarized, it will depolarize the first node of Ranvier; however, as it is a rapidly adapting fibre, this does not carry on indefinitely, and the signal propagation ceases. This is a graded response, meaning that the greater the deformation, the greater the generator potential. This information is encoded in the frequency of impulses, since a bigger or faster deformation induces a higher impulse frequency. Action potentials are formed when the skin is rapidly distorted but not when pressure is continuous because of the mechanical filtering of the stimulus in the lamellar structure. The frequencies of the impulses decrease quickly and soon stop due to the relaxation of the inner layers of connective tissue that cover the nerve ending.

Discovery

Pacinian corpuscle is the first cellular level sensory receptor ever observed by a biologist or an anatomist. It is first discovered by German anatomist and botanist D. Abraham Vater and his student Johannes Gottlieb Lehmann in around 1717 to 1719 and mostly named after

Italian Italian(s) may refer to: * Anything of, from, or related to the people of Italy over the centuries ** Italians, an ethnic group or simply a citizen of the Italian Republic or Italian Kingdom ** Italian language, a Romance language *** Regional Ita ...

anatomist Anatomy () is the branch of biology concerned with the study of the structure of organisms and their parts. Anatomy is a branch of natural science that deals with the structural organization of living things. It is an old science, having its ...

Filippo Pacini Filippo Pacini (25 May 1812 – 9 July 1883) was an Italian anatomist, posthumously famous for isolating the cholera bacterium ''Vibrio cholerae'' in 1854, well before Robert Koch's more widely accepted discoveries 30 years later. Pacini was born ...

for its third re-discovery in 1830. In between around 1820, it is also re-discovered by John Shekleton, a curator of the Royal College of Surgeons in Ireland. Similar to Pacinian corpuscles Herbst corpuscles and Grandry corpuscles are found in avian species.

Additional images

File:Gray940.png, Diagrammatic sectional view of the skin (magnified) File:Vater Pacini Körperchen.png, Schema (German) File:WVSOM Pacinian Corpuscle.JPG, Light micrograph showing three corpuscles in the center of the field File:Histology of a Pacinian corpuscle.jpg, Micrograph of a Pacinian corpuscle

References

External links

Virginia Commonwealth University
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{{DEFAULTSORT:Pacinian Corpuscle Sensory receptors