Friday, June 1, 2007

How Sensitive are the Fingertips?

Most people take for granted the amazing design of the human hand, and how sensitive the fingertips can be.

ChatNChill - The human hand has a particularly refined sense of touch. According to Smithsonian magazine, researchers found that our hand can detect a dot just three microns high. (A human hair has a diameter of 50 to 100 microns.) However, by "using a texture rather than a dot, the researchers found the hand can detect roughness just 75 nanometers high"—a nanometer being one thousandth of a micron! Such remarkable sensitivity is attributed to about 2,000 touch receptors in each fingertip.

Certain functions once lumped together under touch are now regarded as senses in their own right. For instance, pain receptors respond to and distinguish between mechanical, thermal, and chemical forces or agents. Other sensors signal an itch. Evidence suggests that we have at least two kinds of pressure sensors—one for light surface pressure, another for deep stimulation.

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