Touch- by Joanne and Shona

Here is what our crack team of researchers discovered about how the sense of touch works:

Stimulus is sensed through the skin by a nerve ending located in the 2nd layer of our skin, callled the dermis. The stimulation of the nerve creates an electrical impulse that runs down the nerve to the central nervous system located in the spinal cord (missing from the mental model we drew on the board last week). From there the signal travels up the spinal cord to the cerebral cortex in the brain where it is interpreted.
The electrical impulse created from touching something rough is different from the electrical impulse created by something smooth, and hence the brain can distinguish between the two. There are different kinds of receptors to sense different sorts of stimuli. Heat, cold, heavy pressure and light pressure, are all sensed by different types of nerve endings. An overstimulation of any one of these nerve receptors will be registered as something between tickle, itch or pain.
Other fun facts:
-the parts of the body with the most nerve endings are: tongue, lips, face, neck, fingertips, hands and feet.
-the least amount of nerve endings are found in the middle of the back.
-somatic sense: more complete term used in medicine that describes the sense of touch described above, but also includes the sensations we have of the inside of our bodies, such as muscle movement, joint position and stomachaches.

Sources:
"mechanoreception." Encyclopædia Britannica. 2008. Encyclopædia Britannica Online. 13 Jan. 2008 <http://search.eb.com/eb/article-64717>.
http://library.thinkquest.org/3750/touch/touch.html