The Pacinian corpuscle (also lamellar corpuscle, or Vater–Pacini corpuscle) is a low-threshold

mechanoreceptor A mechanoreceptor, also called mechanoceptor, is a sensory receptor that responds to mechanical pressure or distortion. Mechanoreceptors are located on sensory neurons that convert mechanical pressure into action potential, electrical signals tha ...

responsive to vibration or pressure, found in the skin and other internal organs. In the skin it is one of the four main types of

cutaneous receptor A cutaneous receptor is a sensory receptor found in the skin that provides information about temperature, touch (including vibration and pain), spatial orientation,pressure (stretching or squeezing), and metabolic circumstances (including those i ...

s. The corpuscles are present in

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 animal coverings, such as the arthropod exoskeleton, have different ...

notably on both surfaces of the hands and feet, arms, and neck. Pacinian corpuscles are also found on bone periosteum, joint capsules, the

pancreas The pancreas (plural pancreases, or pancreata) is an Organ (anatomy), organ of the Digestion, digestive system and endocrine system of vertebrates. In humans, it is located in the abdominal cavity, abdomen behind the stomach and functions as a ...

and other internal organs, the

breast The breasts are two prominences located on the upper ventral region of the torso among humans and other primates. Both sexes develop breasts from the same embryology, embryological tissues. The relative size and development of the breasts is ...

, genitals, and

lymph nodes A lymph node, or lymph gland, is a kidney-shaped Organ (anatomy), organ of the lymphatic system and the adaptive immune system. A large number of lymph nodes are linked throughout the body by the lymphatic vessels. They are major sites of lymphoc ...

. Pacinian corpuscles are rapidly adapting mechanoreceptors. As phasic receptors they respond quickly but briefly to a stimulus with the response diminishing even when the stimulus is maintained. They primarily respond to

vibration Vibration () is a mechanical phenomenon whereby oscillations occur about an equilibrium point. Vibration may be deterministic if the oscillations can be characterised precisely (e.g. the periodic motion of a pendulum), or random if the os ...

, and deep pressure. They are especially sensitive to high-frequency vibrations. Groups of corpuscles sense pressure changes (such as on grasping or releasing an object). They are additionally crucially involved in

proprioception Proprioception ( ) is the sense of self-movement, force, and body position. Proprioception is mediated by proprioceptors, a type of sensory receptor, located within muscles, tendons, and joints. Most animals possess multiple subtypes of propri ...

. The vibrational role may be used for detecting surface texture, such as rough and smooth.

Structure

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

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 th ...

s and Ruffini's corpuscles. They may measure up to 2 mm in length, and nearly 1 mm in diameter. They are oval, spherical, or irregularly coiled in shape. Larger ones are visible to the naked eye. They have large receptive fields - as large as half of the palm. In the skin, the corpuscles are situated deep within the

dermis The dermis or corium is a layer of skin between the epidermis (skin), epidermis (with which it makes up the cutis (anatomy), cutis) and subcutaneous tissues, that primarily consists of dense irregular connective tissue and cushions the body from s ...

Axon terminal

Each corpuscle is associated with a myelinated axon; these are some of the largest and fastest-conducting sensory axons arising from the skin. Towards the center of the corpuscle, the axon loses its sheaths, ending as with a slight bulge at the center of the corpuscle. This axon terminal issues brief projections of unknown functional significance into gaps between the surrounding innermost lamellae; large mitochondria and small vessels aggregate near these projections.

Capsule

The capsule consists of 20-70 concentrically-arranged connective tissue lamellae around the axon terminal at its center, forming a structure much like an onion. The capsule consists of fibroblasts and fibrous connective tissue (mainly Type IV and Type II collagen network), separated by gelatinous material, more than 92% of which is water. It presents a

whorl A whorl ( or ) is an individual circle, oval, volution or equivalent in a whorled pattern, which consists of a spiral or multiple concentric objects (including circles, ovals and arcs). In nature File:Photograph and axial plane floral diagra ...

ed pattern on

micrograph A micrograph is an image, captured photographically or digitally, taken through a microscope or similar device to show a magnify, magnified image of an object. This is opposed to a macrograph or photomacrograph, an image which is also taken ...

s. If the corpuscle's capsule is experimentally removed, the divested axon terminal becomes slowly adapting. The capsule is therefore responsible for the corpuscle's selectivity for high-frequency stimuli. This is a result of the slippery lamellae sliding past each other when the corpuscle is structurally deformed by external pressure so that effects of sustained pressure are soon dissipated by the lamellae, abolishing deformation of the central axon terminal itself. The capsule thus acts as a physiological

high-pass filter A high-pass filter (HPF) is an electronic filter that passes signals with a frequency higher than a certain cutoff frequency and attenuates signals with frequencies lower than the cutoff frequency. The amount of attenuation for each frequency ...

Function

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

. 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. The 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 capsule). 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.

Sensory transduction

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 receptor potentials. This process is called sensory transduc ...

and causes it to bend or stretch. When the lamellae are deformed, due to either application or release of pressure, a generator or receptor potential is created as it physically deforms the plasma membrane of axon terminal, making it "leak" different cations through

mechanosensitive channels Mechanosensitive channels (MSCs), mechanosensitive ion channels or stretch-gated ion channels are membrane proteins capable of responding to mechanical stress over a wide dynamic range of external mechanical stimuli. They are present in the mem ...

which initiates the

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 ...

. This initial

is potentiated by voltage-activated ion channels present in the inner-coreof the corpuscle. Finally, the receptor potential is modulated to neural spikes or

action potential An action potential (also known as a nerve impulse or "spike" when in a neuron) is a series of quick changes in voltage across a cell membrane. An action potential occurs when the membrane potential of a specific Cell (biology), cell rapidly ri ...

with the help of opening of sodium ion channels present at the first Ranvier's Node of the axon. Due to generation of receptor potential in the receptive area of the neurite (especially near the heminode or half-node of the axon) the potential at the first Ranvier's node can reach certain threshold, triggering nerve impulses or action potentials at the first

node of Ranvier 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 axonal domains that are high in sodium and potassium ion channels co ...

. The first Ranvier's node of the

myelin Myelin Sheath ( ) is a lipid-rich material that in most vertebrates surrounds the axons of neurons to insulate them and increase the rate at which electrical impulses (called action potentials) pass along the axon. The myelinated axon can be lik ...

ated section of the neurite is often found inside the capsule. This impulse is then transferred along the axon from node to node 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.

Surface vibrations

The Pacinian corpuscles in

elephant Elephants are the largest living land animals. Three living species are currently recognised: the African bush elephant ('' Loxodonta africana''), the African forest elephant (''L. cyclotis''), and the Asian elephant ('' Elephas maximus ...

feet have been suggested to enable

seismic communication Seismic or vibrational communication is a process of conveying information through mechanical (seismology, seismic) vibrations of the substrate. The substrate may be the earth, a plant stem or leaf, the surface of a body of water, a spider's web, ...

. The Pacinian corpuscles in mice can detect taps on a branch 2.5 meters away.

History

Pacinian corpuscles were the first cellular sensory receptor ever observed. They were first reported by German anatomist and botanist Abraham Vater and his student Johannes Gottlieb Lehmann in 1741, but ultimately named after Italian

anatomist Anatomy () is the branch of morphology concerned with the study of the internal 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 scien ...

Filippo Pacini, who rediscovered them in 1835. John Shekleton, a curator of the Royal College of Surgeons in Ireland, also discovered them before Pacini, but his results were published later. Similar to Pacinian corpuscles, Herbst corpuscles and Grandry corpuscles are found in

bird Birds are a group of warm-blooded vertebrates constituting the class (biology), class Aves (), characterised by feathers, toothless beaked jaws, the Oviparity, laying of Eggshell, hard-shelled eggs, a high Metabolism, metabolic rate, a fou ...

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