6.1.7 The Pacinian Corpuscle

• Humans possess a wide range of receptor cells that can detect and respond to a large variety of stimuli
  • For example, temperature, taste, sound, heat and light

• This is highly beneficial as it allows for an organism to differentiate between the different external and internal environmental conditions
• Each receptor will only respond to a specific stimulus

The sense of touch

• Through their sense of touch, humans are able to distinguish between many different sensations
  • The skin can be touched using different pressures such as a light touch or a jab with a sharp object - different levels of pressure feel different
  • The temperature of the surrounding air can be detected by the skin - warm and cold air feel different

• All the different sensations are detected by different types of receptors found within the skin

Pacinian corpuscles

• In any area of the skin, there are a range of different receptors present
• The number of receptors present can vary in different areas of the skin
  • The fingertips have a very large number of receptors
  • The back of fingers have a much lower number of receptors

• The different receptors have different structures and positions within the skin
• Pacinian corpuscles are a type of receptor found deep in the skin
  • They are present in the skin of fingers, soles of the feet as well as in joints, tendons and ligaments.
  • They respond to changes in pressure
  • When these receptors are stimulated by pressure on the skin it leads to the establishment of a generator potential

Different skin receptors are found in different regions and have different structures

• Pacinian corpuscles have quite a complex structure
  • They are technically not a separate cell, they are found at the ends of sensory neurone axons

• They are made of many layers of membrane separated by a gel
  • It can look like an onion
  • The gel between the layers contains positively charged sodium ions (Na⁺)

• The section of axon surrounded by layers of membrane contains stretch-mediated sodium ion channels which open when sufficient pressure is applied
• When pressure receptors are stimulated by pressure on the skin an electrical potential difference across the axon membrane is established - the generator potential

The axon of the sensory neurone is surrounded by layers of membrane