Sunday, March 11, 2007

nerve action - sound vs electricity

Leon Brooks linked to this article claiming that sound not electricity travels through nerves.

When you put a moderate voltage through your body it will cause muscle action (try putting 1000V at low current between fingers of the same hand for safety). The original experiment that suggested that electricity is used involved applying a shock to the legs of a dead frog (see the Wikipedia entry for Luigi Galvani).

For this claim about sound to be valid the electric shocks would have to cause sound in the nervous system. Also sound impulses would have to trigger nerve action (IE the "brown note"). AFAIK neither of these have been proven.


Madeleine said...

On top of their failure to explain away decades of meticulous research on things like how neurotransmitters seem to induce action potentials through binding ligand-mediated ion channels, I'm suspicious of their "reasoning from first principles". The "voltage theory"[1] involves the maintenance of a constant voltage over the cell membrane, and an "action potential" is the release and loss of that difference. The ions return to a state of higher entropy, not unlike releasing high pressure gas from a cylinder or dissolving salt in water. These things are chilling endothermic processes, not exothermic. I would hypothesize that the heat that is generated would be constantly generated during the maintenance of this voltage difference, not during the release as neurons fire.

[1] Gravity is also a "theory".

Kelly said...

As noted by some on slashdot ( ), the CBC article is not an accurate summary of the paper. I read part of the paper and I am not able to fully understand what they are talking about, but it is not what CBC said it was.

etbe said...

One point that didn't occur to me when writing the article (and which ties in with Madeline's points) is the amounts of energy involved.

Would the amounts of energy involved in nerve activity be enough to cause much warming? Given that nerves in a functioning body will be surrounded by other organs that produce heat for a variety of reasons it will be difficult to determine which heat is produced where, and to even measure the small changes in temperature that are caused.

Madeleine said...

Oops. Thanks, Kelly. Sorry, I hadn't realized how bad that CBC article was. The actual paper is totally different, I think it's just observing that general anesthetics have effects on lipid membrane phase transiption -- and this is "heretical" because mostly people look for binding to ion channels. Nothing about "electricity generates heat", and I only saw one sentence about "solitons"... and I'd personally be tempted to speculate that anesthetics have a systems effect on membrane protein diffusion? (Assuming these phase transitions affect that? Nothing on diffusion was in the paper.) This definitely isn't "news" unless they find something like a signalling protein that detects the lipid phase changes or actually observe some significant phase change propagations in real neurons.