6.1.7 The Pacinian Corpuscle

Structure and Location

• Found deep in the skin, particularly on the fingers, soles of feet, and external genitalia.
• Also located in joints, tendons, and ligaments to detect changes in pressure during movement.
• Consists of a single sensory neurone surrounded by layers of connective tissue called lamellae, separated by a gel.

Mechanism of Action

1. Resting State:

• The membrane of the sensory neurone contains stretch-mediated sodium channels, which are normally closed in the absence of pressure.

2. Pressure Applied:

• When pressure is applied to the Pacinian Corpuscle, the lamellae become deformed, causing the stretch-mediated sodium channels to open.

3. Sodium Ion Influx:

• Sodium ions (Na⁺) rapidly diffuse into the sensory neurone.
• This influx causes the membrane potential to become depolarised, creating a generator potential.

4. Action Potential:

• If the generator potential reaches the threshold level, an action potential is initiated in the sensory neurone.
• This action potential travels along the neurone to the central nervous system (CNS), where the stimulus is processed.

Key Features

• Specificity:
  • The Pacinian Corpuscle is highly specialised to detect mechanical pressure or vibration, and will not respond to other types of stimuli (e.g., temperature).
• Adaptation:
  • It stops responding to sustained pressure, ensuring the receptor is sensitive to changes rather than constant stimuli.