AQA A Level Biology复习笔记6.1.7 The Pacinian Corpuscle

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

     

Skin-receptors

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

 

The Structure of a Pacinian Corpuscle

  • 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

Structure-of-Pacinian-corpuscle

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

 

Exam Tip

For exam questions, you may be asked to explain why there are so many different receptor types. This is because receptors detect and respond to a specific stimulus so multiple receptors are required to respond to multiple stimuli.

 

 

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