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Like Ruffini endings, they are found in deep subcutaneous tissue, and are considered rapidly adapting receptors, which means they will not fire action potentials throughout the duration of a stimulus but, rather, will fire briefly at its beginning and end (Kandel et al., 2000).
Similar in physiology to the Meissner's corpuscle, Pacinian corpuscles are larger and fewer in number than both Merkel cells and Meissner's corpuscles (Kandel et al., 2000).
The Pacinian corpuscle is oval shaped and approximately 1 mm in length. The entire corpuscle is wrapped by a layer of connective tissue. It has 20 to 60 concentric lamellae composed of fibrous connective tissue and fibroblasts, separated by gelatinous material. The lamellae are very thin, flat, modified Schwann cells. In the center of the corpuscle is the inner bulb, a fluid-filled cavity with a single afferent unmyelinated nerve ending.
Pacinian corpuscles detect gross pressure changes and vibrations. Any deformation in the corpuscle causes action potentials to be generated, by opening pressure-sensitive sodium ion channels in the axon membrane. This allows sodium ions to influx in, creating a receptor potential.
These corpuscles are especially susceptible to vibrations, which they can sense even centimeters away (Kandel et al., 2000). Pacinian corpuscles cause action potentials 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 (Kandel et al., 2000). It is thought that they respond to high velocity changes in joint position.
Pacinian corpuscles have a large receptive field on the skin's surface with an especially sensitive center (Kandel et al., 2000). They only sense stimuli that occur within this field.
The term "Golgi-Mazzoni corpuscle" (distinct from the Golgi organ) is used to describe a similar structure found only in the fingertips. (c_56/12261088 at Dorland's Medical Dictionary, synd/2423 at Who Named It)
|This article is licensed under the GNU Free Documentation License. It uses material from the Wikipedia article "Pacinian_corpuscle". A list of authors is available in Wikipedia.|