: Nerves Transmit Sound, Not Electricity

[Guest guest]

Comments?

Misty L. Trepke

http://health.

 

Controversial New Idea: Nerves Transmit Sound, Not Electricity

Robert Roy Britt

LiveScience Managing Editor

LiveScience.com

Sat Mar 17, 10:05 AM ET

 

http://news./s/livescience/20070317/sc_livescience/controver

sialnewideanervestransmitsoundnotelectricity

 

 

Nerves transmit sound waves through your body, not electrical

pulses, according to a controversial new study that tries to explain

the longstanding mystery of how anesthetics work.

 

 

Textbooks say nerves use electrical impulses to transmit signals

from the brain to the point of action, be it to wag a finger or

blink an eye.

 

 

" But for us as physicists, this cannot be the explanation, " says

Thomas Heimburg, a Copenhagen University researcher whose expertise

is in the intersection of biology and physics. " 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. "

 

 

The textbooks are not likely to be rewritten anytime soon, however.

 

 

Roderic Eckenhoff, a researcher in the Department of Anesthesiology

and Critical Care at the University of Pennsylvania School of

Medicine, called the sound pulse idea interesting. " But an enormous

burden of proof exists and they have a very long way to go to beat

electricity, " he said.

 

 

The olive oil clue

 

 

Nerves are wrapped in a membrane of lipids and proteins. Biology

textbooks say a pulse is sent from one end of the nerve to the other

with the help of electrically charged salts that pass through ion

channels in the membrane. But the lack of heat generation

contradicts the molecular biological theory of an electrical impulse

produced by chemical processes, says Heimburg, who co-authored the

new study with Copenhagen University theoretical physicist Andrew

Jackson.

 

 

Instead, nerve pulses can be explained much more simply as a

mechanical pulse of sound, Heimburg and Jackson argue. Their idea

will be published in the Biophysical Journal.

 

 

Normally, sound propagates as a wave that spreads out and becomes

weaker and weaker. But in certain conditions, sound can be made to

travel without spreading and therefore it retains its intensity.

 

 

The lipids in a nerve membrane are similar to olive oil, the

scientists explain. And the membrane has a freezing point that is

precisely suited to the propagation of these concentrated sound

pulses [graphic].

 

 

Eckenhoff is not convinced, however.

 

 

" It is difficult to explain away an enormous number of real

electrical recordings in the cell, tissue and whole animal as being

some kind of artifact, " Eckenhoff told LiveScience. " And I cannot

easily discern how the sound might be generated. "

 

 

Explaining anesthesia

 

 

The idea from Heimburg and Jackson, if it were proven true, could

have implication for anesthetics, another mysterious process.

 

 

Oddly, scientists don't understand exactly what happens when a

patient is anesthetized. While the goal of an anesthetic is to

prevent the brain from feeling pain, the drugs can affect a

patient's heart rate and breathing. So a better understanding of how

it all works would allow development of better drugs.

 

 

Researchers do know that the proper doses of ether, laughing gas,

chloroform and other anesthetics are all based on their solubility

in olive oil. But how the nerves are turned off is a mystery.

 

 

Heimburg and Jackson offer an explanation.

 

 

If a nerve is to be able to transport sound pulses, they say, then

the melting point of its membrane must be close to body temperature.

Anesthetics change the melting point so that sound pulses can't

propagate, they conclude. Nerves are put on stand-by and a patient

doesn't feel the knife slicing into his body.

 

While Eckenhoff acknowledges there is much to learn, he expects the

precise effects of anesthesia will ultimately be explained by an

integration of current theories rather than by employing the new

idea of sound pulses.

 

Visit LiveScience.com for more daily news, views and scientific

inquiry with an original, provocative point of view. LiveScience

reports amazing, real world breakthroughs, made simple and

stimulating for people on the go. Check out our collection of

Science, Animal and Dinosaur Pictures, Science Videos, Hot Topics,

Trivia, Top 10s, Voting, Amazing Images, Reader Favorites, and more.

Get cool gadgets at the new LiveScience Store, sign up for our free

daily email newsletter and check out our RSS feeds today!