Merkel  “Touch Cells”

This blog is a simplified version of a review on Merkel touch cells that was written for PhD level scientists.  Part of the AZ science requirements for middle school kids are good and kind of crazy at the same time.  They are good because they introduce kids to just how mind boggling and complex the world around us and within us really is.  On the other hand, they are kind of crazy because of the burden they place on middle school teachers in particular.

This is a link to my source.

Woo SH, Lumpkin EA, Patapoutian A. (2015) Merkel cells and neurons keep in touch. Trends Cell Biol. 25(2):74-81. Free Paper

What is a Merkel Cell?

“Within cells, special structures are responsible for particular functions, and the cell membrane forms the boundary that controls what enters and leaves the cell.”  AZ science requirements…

Characteristics of resting Merkel cells

• More sodium and calcium ions outside the cell.
• A net positive charge outside the cell membrane
• A net negative charge inside the cell membrane.  We say that the membrane is “polarized”
• Vesicles containing neurotransmitters are not moving.

Characteristics of touch activated Merkel cells

• Piezo2 ion channels are open and letting calcium and sodium into the cell
• the vesicles containing neurotransmitters start to move
• The  membrane “depolarizes.”
• Voltage gated calcium channels open, but we will set this aside until college.

Merkel cell history and present

•  Friedrich Sigmund Merkel was the first to describe these “Tastzellen” (touch cells) in 1875.
• Merkel hypothesized that these cells were responsible for the touch sensation.  (1) Touch cells are close to nerve fibers.  (2) They are abundant in touch-sensitive areas of the skin, such as fingertips, lips, and specialized spots in hairy skin called touch domes.
• In 1969, A Iggo and R Muir were the first to prove that pressing on Merkel cells sent electrical currents down neurons they they were connected to.
• The contacts between Merkel cells and nerves are similar to synaptic contacts between two neurons.

How do Merkel cells talk to our brains?

“Each sense receptor responds to different inputs (electromagnetic, mechanical, chemical), transmitting them as signals that travel along nerve cells to the brain. The signals are then processed in the brain, resulting in immediate behaviors or memories. Changes in the structure and functioning of many millions of interconnected nerve cells allow combined inputs to be stored as memories for long periods of time.”  AZ science requirements

We are going to skip a lot of complicated stuff in this animation.

How does light touch open these  Piezo2 channels that allow sodium and calcium ions to enter the Merkel cells?  Scientists have some pretty good hypotheses that are beyond the education of middle and high school kids.