5.3.2 Mammalian Sensory Receptors

• A cell that responds to a stimulus is called a receptor cell
• Receptor cells are transducers – they convert energy from one form (such as light, heat or sound) into energy in an electrical impulse within a sensory neurone
• Each receptor will only respond to a specific stimulus

Receptors of the body act as transducers

Receptors of the Body and their Stimuli Table

Pacinian corpuscles

• In any area of the skin, there are a range of different receptors present
• The different receptors have different structures and positions within the skin
• Pacinian corpuscles are a type of mechanoreceptor 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 are found at the ends of sensory neurone axons
• They are not a separate cell, but instead are made of many layers of membrane around the end of the neurone separated by a gel
  • 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
• This allows (Na⁺) to flow into the neurone, so that 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

The process of converting mechanical pressure into a nervous impulse in a Pacinian corpuscle