Scientists say nerves use sound, not electricity
Last Updated: Friday, March 9, 2007 | 7:13 PM ET
CBC News <http://www.cbc.ca/technology/story/2007/03/09/science-
nervessound-20070309.html>

The common view that nerves transmit impulses through electricity is
wrong and they really transmit sound, according to a team of Danish
scientists.

The Copenhagen University researchers argue that biology and medical
textbooks that say nerves relay electrical impulses from the brain to
the rest of the body are incorrect.

"For us as physicists, this cannot be the explanation," said Thomas
Heimburg, an associate professor at the university's Niels Bohr
Institute. "The physical laws of thermodynamics tell us that
electrical impulses must produce heat as they travel along the nerve,
but experiments find that no such heat is produced."

Heimburg, an expert in biophysics who received his PhD from the Max
Planck Institute in Goettingen, Germany — where biologists and
physicists often work together in a rare arrangement — developed the
theory with Copenhagen University's Andrew Jackson, an expert in
theoretical physics.

According to the traditional explanation of molecular biology, an
electrical pulse is sent from one end of the nerve to the other with
the help of electrically charged salts that pass through ion channels
and a membrane that sheathes the nerves. That membrane is made of
lipids and proteins.

Heimburg and Jackson theorize that sound propagation is a much more
likely explanation. Although sound waves usually weaken as they
spread out, a medium with the right physical properties could create
a special kind of sound pulse or "soliton" that can propagate without
spreading or losing strength.

The physicists say because the nerve membrane is made of a material
similar to olive oil that can change from liquid to solid through
temperature variations, they can freeze and propagate the solitons.

The scientists, whose work is in the Biophysical Society's
Biophysical Journal, suggested that anesthetics change the melting
point of the membrane and make it impossible for their theorized
sound pulses to propagate.

The researchers could not immediately be reached for comment.

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20070309.html>