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    Saturday, March 17, 2007

    Nerve Physics: Do nerves use sound to communicate? The theory is based on the assumption that too little heat is generated by the process for it to be electrical. (But those electrical impulses have actually been, you know, measured.) Let's ask the resident physicist, Mr. Medpundit:

    "As I understand it, the nerves use an electrical signal, but not an electrical current like the ones that flow down a wire. The passage of electrical signals in a nerve is more like a wave than a current. Imagine lining up a bunch of safety patrol kids along the street and sending a "GO" signal from the beginning of the line to the end. That could be done two ways. The kids could pass one "GO" sign from the first kid in line down to the last kid. That's how an electrical signal flows in a current. The other way would be to have each kid hold their own sign. The first kid rasies his sign which is the signal for the next kid to raise his and so it goes on down the line to the end - the wave. As an electrical impulse, the wave generates less heat because the motion of individual electrons is only across the cell membrane, not along the distance of the nerve. They may just be theorizing too much heat. And besides, sound waves generate heat, too"

    I think he's right. He always is.

    posted by Sydney on 3/17/2007 09:42:00 PM 3 comments


    I'm so glad somebody else thinks that the announcement of sound and nerves was as silly as I thought it was.

    It was my understanding that they dont conduct electricity so much as cause ions to flow across the membrane which gives the cell a bit of a charge, enough for the next cell to pick up on that and make it's ions move through it's membranes and so on down the line.

    so another triumph of science by press release ;)

    By Anonymous PlanetaryGear, at 9:57 AM  

    The real counterproof is long, unmyelinated axons. The signal propagates too far and too slowly to be carried by any reasonable acoustic process.

    By Anonymous dn, at 6:32 PM  

    I'll nitpick here just a little. Here's what we're learning in my M1 neuro class: First of all, there are no electrons involved in nerve conduction. What causes depolarization across a membrane is the movement of positively charged ions (specifically sodium) through ion-channels in the cell. Depolarization at one spot activates ion channels further down the cell, which is what causes the wave-like effect. Secondly, the wave doesn't propogate from nerve cell to nerve cell like a sound wave. The depolarization at the end of one nerve cell causes the release of neurotransmitters that are taken up by the next nerve cell. So, it's a chemical process, which is another reason it can be pretty slow.

    By Blogger Josh Mugele, at 12:04 PM  

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