Mammalian Sensory Receptors (OCR A Level Biology): Revision Note

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 connect to sensory neurones

• They consist of many layers of membrane around the end of the neurone

  • The layers are separated by a gel

  • The gel contains positively charged sodium ions (Na⁺)

• The section of neurone 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 is established across the cell membrane; this is a generator potential

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

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