Notes

Sensory Receptors

• Vision, Smell, Taste, Touch, Thermal Senses, Pain, Hearing, Balance, Proprioception.
• The Somatosensory encapsulated receptors are 4:
  • Meissner Corpuscle
  • Merkel-Neurite Complex
  • Ruffini Corpuscle
  • Pacinian Corpuscle

Some of these receptors quickly adapt, while others don't. Fibers are classified as either:

• Rapidly Adapting (RAs)
• Slowly Adapting (SAs)
• Also in terms of the size of their Receptive Field (The size of the area on the skin from which they can be activated) (it is also related to the position of the receptor, indeed superficial receptors tend to have smaller RF than deeper ones).

RAs respond only at the beginning and end of sustained displacements (i.e., to transients) but respond well to higher frequency vibrations. Two types:

• RA I: Meissner Corpuscles (10 - 200 Hz) (small RF)
• RA II (PC): Pacinian Corpuscles (70 - 1000 Hz) (large RF)

SAs respond throughout sustained displacements of the skin, and are thus suited to coding the duration and magnitude of mechanical stimuli. Two types:

• SA I: Merkel Receptors/Disks (small RF)
• SA II: Ruffini Endings (large RF).