The Pacinian corpuscle is a specialized sensory nerve ending, classified as a mechanoreceptor. It converts mechanical stimuli, such as pressure and vibration, into electrical signals that the brain can interpret. As one of the four main types of cutaneous receptors, it contributes to our ability to perceive the physical world.
Location in the Body
Pacinian corpuscles are widely distributed throughout the human body, found in both hairy and hairless skin. They are particularly prevalent in the deeper layers of the skin, specifically the dermis and hypodermis, especially in areas like the palms of the hands, soles of the feet, and fingertips. They are also present in other tissues, including joint capsules, ligaments, tendons, bone periosteum, and internal organs such as the pancreas, breast, and genitals. Their widespread distribution enables them to contribute to sensations beyond surface touch, including proprioception (awareness of body position).
Detecting Touch and Vibration
The Pacinian corpuscle is primarily involved in detecting high-frequency vibration and deep pressure. It is a rapidly adapting mechanoreceptor, meaning it responds strongly to the onset and offset of a stimulus but quickly stops responding if the stimulus is sustained. This rapid adaptation makes it particularly effective at sensing changes in pressure rather than constant pressure.
This allows us to perceive textures by feeling vibrations as our fingertips move across a surface. The Pacinian corpuscle is highly sensitive to vibrations, with optimal sensitivity around 250 Hz, which is a frequency range generated by fine textures. These corpuscles also enable us to feel the vibration of a phone or the deep poke of an object. Furthermore, they contribute to our ability to grip objects by sensing pressure changes.
How the Pacinian Corpuscle Works
The Pacinian corpuscle has a unique onion-like structure, consisting of a single sensory nerve fiber surrounded by 20-70 concentric layers of connective tissue, called lamellae. These layers are separated by a fluid-filled space. When mechanical pressure or vibration is applied to the corpuscle, it deforms these outer layers, transmitting the mechanical force to the central nerve ending within the corpuscle.
The distortion of the nerve ending’s membrane causes mechanically-gated ion channels to open. The influx of ions, primarily sodium, creates an electrical change called a generator potential. If this generator potential reaches a certain threshold, it triggers an action potential, which is a nerve impulse, that travels along the sensory neuron to the brain for interpretation. The layered capsule acts as a mechanical filter, allowing only transient disturbances and high-frequency stimuli to effectively deform the nerve ending, which explains its rapid adaptation and sensitivity to vibration.