Mapping Receptors for Light Touch

The body distinguishes light touch from deep pressure and pain based on the somatosensory receptor anatomy, location, afferent nerve tract, and final interpretation in the parietal lobes of the brain's somatosensory cortex in order to properly interact with environmental stimuli. Light touch receptors in the skin are associated with the merkel disc located in the dermal papilla of the skin.

Materials:

Testing Partner
Hand Lotion
Washable marker (fine point)
Cat Whisker, Horse Hair or a Bristle from a stiff brush
Test subject forearm and posterior back (shoulder area)
Metric ruler

Procedure:
Apply hand lotion to the subject's forearm.
Draw a 2.5cm x 2.5cm square (1" x 1") on the anterior surface
Have test subject close eyes.
Testing partner will use the fine point marker to record (dot) the location of a positive light touch perception
Record the number of positive responses. ___________

Repeat procedure using the back shoulder area of the subject.
Record the number of positive responses. ___________

Assessment:

a) How did the number of positive responses compare?

b) Why do you think you got those results?

c) Where on the body would you most likely find the most number (receptor density) of merkel receptors?