Tuesday, June 23, 2009

A light touch

There's a recent piece in Science News about the sensation of light touch in the skin. It includes some nifty sound files that allow a person to hear the signals for light touch sent by tactile disc complex of the skin.

As you may recall from my textbook Anatomy & Physiology, the sensory structure for light touch is comprised of two pieces: a tactile epithelial cell and a (tactile disc) sensory nerve ending. The former is often also called a Merkel cell and the latter a Merkel disc. These two pieces working together can be called a epithelial tactile complex or a Merkel disc complex.

The Merkel name comes from the German anatomist Friedrich Merkel, who in 1872 was the first to describe what we now know as Merkel cells. But these days, the international list of anatomical terms (Terminologia histologica) avoids the eponym and instead uses descriptive names.

The Science News article summarizes some recent research that helps to further clarify the mechanisms of how the sensory complex for light touch actually works. Specifically, it outlines how the tactile epithelial cells release glutamate, a neurotransmitter, that may communicate with the sensory neuron to send the signals needes to transmit the sensation of light touch.

The article further describes some gene-knockout experiments that help to prove that light touch cannot be perceived without the tactile epithelial cells to work along with the sensory neurons.

As the article points out, there is still much to learn about the mechanisms of light touch and the specific and detailed roles of the cells involved in sensation.

Want to know more? Check these out:

A Role for Merkels
Tina Hesman Saey
Science News, published online 18 June 2009
[Article summarizing recent research into the role of tactile epithelial cells.]

To listen to samples of tactile epithelial (Merkel) cells and the signals they generate, please click here.

Merkel Cells Are Essential for Light-Touch Responses
Stephen M. Maricich et al.
Science 19 June 2009:Vol. 324. no. 5934, pp. 1580 - 1582
DOI: 10.1126/science.1172890
[The original research report; also includes a link to a podcast.]

There's a great FREE animation of the light touch mechanism at YouTube but the narration is in German. In an English-only classroom, using the video with the narration muted might work well. Click here for the video.

If you missed my recent article Fingerprint functions about the role of epidermal ridges in sensation (lamellar corpuscle function) click here to read it.

If you're like me and a fan of A&P history or eponyms, or both, then click on the portrait of Merkel (click here if you can't see it in your news feed) for a FREE image you can use in your classroom presentation or course website.

My textbook Anatomy & Physiology includes nice diagrams of the light touch structures in Chapters 6 and 15 (the digital file is in the FREE Instructor's Resource CD).

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