• 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