w1z4rd
Valued Senior Member
Scientists say nerves use sound, not electricity
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I really dislike stuff like this. Theoretical physicists who think they know more than any other type of scientist simply because they are …. (gasp and awe) ..... physicists! 
This is just another instance of people trying to generate some media buzz over nothing.
Propagation of membrane potentials by salutatory conduction along axons (ie. electrical nerve impulses) is confirmed countless times every day all over the world via the endless scientific experiments and medical procedures that are based on that theory. Every level of biology (from the genetic level to the biochemical level to the cellular level to the whole organism level) confirms the electrical impulse theory.
And here’s the clincher…
This is just another instance of people trying to generate some media buzz over nothing.It’s not a “much more likely” explanation at all. Not even slightly. :bugeye:
Propagation of membrane potentials by salutatory conduction along axons (ie. electrical nerve impulses) is confirmed countless times every day all over the world via the endless scientific experiments and medical procedures that are based on that theory. Every level of biology (from the genetic level to the biochemical level to the cellular level to the whole organism level) confirms the electrical impulse theory.
And here’s the clincher…
Oh I see. So in order to substantiate their unproven idea that nerve impulses are actually sound and not electrical in nature, they are invoking an unknown and theoretical set of physiological conditions that must be present in order for their theory to be correct! What absurd circular logic.
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Glad to see you back here active. Perhaps you were in hospital with head injury?
Herk Rock is 110% correct. It is relatively simple to stick micro electrodes into axon and see the -70mV "resting potential" or observe that the concentration of Na+ ions has been reduced compared to the electrolyte outside.
When this neutral sound wave (a soliton of course) comes to a given point on the axon there is a sudden influx of the Na+ to the interior of the axon and often a slight "over shoot" to a few mV positive. The soliton wave can not pass again until the "sodium pump" restores the negative resting potential in the interior by pumping the Na+ back out (called the refractory period).
I wonder why the axon is refractory for a period in that no new soliton wave can travel down it?
Take two asperin, get some more rest, and your brain should recover. - I sure hope so. - You are one of the best thinking and the hardest working posters here.
BTW I think Herk was excessively kind to those idiots. - I bet they do not even know that the first ELECTRICAL oscilloscope was invented two guys trying to measure the speed of those "soliton waves"
It's already known how nerves work. These Danish scientists are wrong.
If it actually were sound instead of electrical potential, then why do anaesthetics such as benzocaine, which work by blocking the sodium channels , work the way they do? The whole purpose of the sodium channel is to regulate the voltage through ions.
Maybe because it's not so much an electrical current as it is a change in voltage. The heat produced would be so very small that they probably just failed to measure it correctly.
Yes. The traditional explanation has been proven and observed time and time again.
If it actually were sound instead of electrical potential, then why do anaesthetics such as benzocaine, which work by blocking the sodium channels , work the way they do? The whole purpose of the sodium channel is to regulate the voltage through ions.
Don't draw conclusions from the media article. I don't think it's an accurate representation of the work it's reporting on... at least, I can't reconcile it with the literature published by Thomas Heinberg.
This article seems to be the seminal work: On soliton propagation in biomembranes and nerves
More recent papers can be found here: Membrane Biophysics Group, Neils Bohr Institute, University of Copenhagen
According to my limited understanding, they do not deny that electrical impulses are involved in nerve transmission. They do claim that they have suggestive evidence that solitons (structured sound waves) could be involved.
As far as i can tell, it's good science. They've followed through on some interesting observations and produced a testable novel theory.
This article seems to be the seminal work: On soliton propagation in biomembranes and nerves
More recent papers can be found here: Membrane Biophysics Group, Neils Bohr Institute, University of Copenhagen
According to my limited understanding, they do not deny that electrical impulses are involved in nerve transmission. They do claim that they have suggestive evidence that solitons (structured sound waves) could be involved.
As far as i can tell, it's good science. They've followed through on some interesting observations and produced a testable novel theory.
It seems to me if this were true if a human were ever to encounter a specific frequency of sound, all their nerves would start firing at once causing a seizure of some sort.
Well, I think it’s a bit harsh to label them as idiots.
And Pete makes a very good point – science journalism is frequently poor and seldom accurately reflects the science that is being reported. It's definitely a trap to judge science based on its media coverage.
It glanced at the PNAS paper that Pete identified as (apparently) the “seminal” on the subject. I have a neuroscience background but for the most part it was unintelligible to me. The subject matter is biophysics which mostly bears no resemblance to “wet” biology. It’s all a bunch of mathematical analyses of isolated lipids in non-physiological conditions, and purely theoretical extrapolations to living organisms. I couldn’t recognize anything that related to in vivo biology.
My overall impression is that it's just a whole lot of hand waving.
I find this slightly harsh. From my experience (I have an ongoing colloboration with one lab) biophysics experiments are not that different from biological ones. There is a difference in interpretation, though. The physicists usually try to derive a mathematical model from the measurements and often check these with theoretical physicists. While one could argue that biological systems are too complicated and so forth, however, I found some models quite helpful.
That being said, I cannot assess the relevance of the paper from the first glance, either...
Ophiolite
Valued Senior Member
Do you think the handwaving is transverse or longitudinal?
Does not matter so long as it is shape preserving.Do you think the handwaving is transverse or longitudinal?
More seriously, perhaps I was too harsh, based on only a press report, without reading more than post 1's:
"...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. ..."
This seems to be stating something truely idiotic. Nerve impulses, are electric depolarization waves. They do have a "soliton constant shape" but so do many waves that have small dispersion, for example, the analogue voice signal in the elephone company's wires.
Hold the presses:
Billy T announces that the copper wires of telephone company are carrying "soliton sound waves" and that is a "much more likely explanation " than the conventional POV that they are electrical signals!
Plus if nerve cells used sound waves wouldnt our reflexes be much much slower than they currently are considering sound moves a lot slower then electricity?
I'm supposed to have a handle on this now.. let's see if I understand it.
The standard model of nerve impulse transmission isn't like electricity through a wire.
A nerve axon is a tube with a negative charge inside. The surface of the tube contains lots of cool protein machinery that can act like switches that can open to allow electricity (different charged ions) to run freely between the inside of the tube and the outside, and like batteries that can force ions in a particular direction.
A nerve impulse (an action potential) is a wave of the switches and batteries opening and shutting.
First, the charge inside the start of the tube changes, becoming less negative.
This change in charge makes some switches open, allowing the charge inside the tube to change a lot, becoming close to neutral or even a bit positive.
This large change in charge is felt a little way along the tube (up to a couple of millimetres in fast myelinated nerves), enough to make the switches there open, and continue the cycle.
The switches don't stay open long, and when they close the little batteries can restore the normal negative charge, ready for another impulse.
The bottom line is that nerve impulses aren't that fast. They propagate at between 1m/s and 100m/s.
Interesting tidbit - we have fast and slow pain fibres that give different sensations.
Have you ever stubbed your toe, or hit your thumb or finger with a hammer?
First you feel the signal from the fast pain fibres - a 'sharp' kind of pain.
Then after a maybe a second, you get the signal from the slow pain fibres - a 'dull', deep, throbbing.
Please check these facts - this post is all from memory of things I'm supposed to have learned last year (except the velocity numbers - I got those from Wikipedia).
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http://en.wikipedia.org/wiki/Soliton_model
Doesn't sound overly crazy to me, in fact it sounds quite plausible.
P.S. We physicists DO know more than any other type of scientist.
Doesn't sound overly crazy to me, in fact it sounds quite plausible.
P.S. We physicists DO know more than any other type of scientist
.
Considering the nerve system can report the location of pain reception or direct the operation of any number of muscles, tendons and overall body movements. Placing a simplified transmission by electricity wouldn't really be feasible, after all that's a lot of different operations that need to be transferred by non-colliding sub-carrier transmissions within a certain frequency range or bandwidth.
what would be rather intriguing is if the location of the stimuli operates based upon a frequency that is interlinked with it's distance to the Cerebral Cortex. This would suggest that the human body reports the equivalent of a holographic representation of the body for processing through the nerve system and is likely constantly updated.
(Incidentally this just proves how theory can go a completely different direction from Biology)
what would be rather intriguing is if the location of the stimuli operates based upon a frequency that is interlinked with it's distance to the Cerebral Cortex. This would suggest that the human body reports the equivalent of a holographic representation of the body for processing through the nerve system and is likely constantly updated.
(Incidentally this just proves how theory can go a completely different direction from Biology)
A few here can believe what they want. But for me, I'll never take the word of any scientist working outside his professional field until it's been verified by other independent researchers (remember cold fusion?). Who here would consider getting the services of a nuclear physicist to have a cornea transplant done??
As a good example of this, who remembers Dr. Linus Pauling? A Nobel prize-winner in chemistry and A man I had admired earlier. He went off into this kick about massive doses of vitamin C preventing the common cold - and wound up being hissed and booed into obscurity. As a professional in inorganic/organic chemistry, his work was absolutely brilliant. But as a biologist and physiologist, he simply didn't have the background needed to pursue work in those areas. Even a highly-skilled rocket scientist doing excellent work for NASA would not be considered knowledgeable enough to do neurobiology work of ANY kind.
So until these guys manage to get the backing of the proper people, I'm going to chalk this whole business up to nothing more than backyard tinkering by unqualified amateurs. :shrug:
As a good example of this, who remembers Dr. Linus Pauling? A Nobel prize-winner in chemistry and A man I had admired earlier. He went off into this kick about massive doses of vitamin C preventing the common cold - and wound up being hissed and booed into obscurity. As a professional in inorganic/organic chemistry, his work was absolutely brilliant. But as a biologist and physiologist, he simply didn't have the background needed to pursue work in those areas. Even a highly-skilled rocket scientist doing excellent work for NASA would not be considered knowledgeable enough to do neurobiology work of ANY kind.
So until these guys manage to get the backing of the proper people, I'm going to chalk this whole business up to nothing more than backyard tinkering by unqualified amateurs. :shrug:
No need to Pete, you have it all correct, but I might add that typically the negative potential inside the tube (nerve axon) is - 70mv. Also there are some details about myelinated vs un-myelinated nerves you did not mention.
All nerves have a capacitance per unit length - the normal axon tube wall boundary is the dielectric, but as you noted, it briefly becomes more conductive for ions during the action potential. (Mainly Na+ ions are rushing to the inside to neutralize the -70mV)
In un-myelinated nerves, this dielectric wall is thin so the capacitance per unit length is much higher than in myelinated nerves, where the swan cells wrapping around the axon greatly increase the thickness of the dielectric wall and thus lower the capacitance per unit length. That is why myelinated nerves are the faster nerves. - Less ion flow needed to change the voltage across the axon cell walls and continue the process of the discharge propagation you described.
The influx of Na+ ions cannot go thru the swan cells but there is a small gap between adjacent swan cells of the myelinated nerves called the "Nodes of Reainer" (but that is my phonetic spelling, and probably not correct) where the Na+ influx takes place.
The swan cells are mainly fat and provide good insulation between adjacent nerves as well as lower the capacitance per unit length to speed signal propagation. Several neurological diseases are caused by dying swan cells, which allow the adjacent nerves to "cross talk" - I.e. one that is not supposed to have an action potential traveling down it will as it is falsely triggered into firing by the changing electric field of the adjacent nerve's action potential.
SUMMARY: The idea that action potentials are sound waves is nonsense. We know, in great detail, exactly how nerves fire. It is possible that as part of this process, the changing electrical stress across the axon wall, could induce very tiny motion, but as it is all in an inter-cellular fluid these weak sound waves, if they exist would be highly damped and are only very secondary to the process.
BTW, did you know that the oscilloscope was invented by two doctors who wanted to measure the speed of action potential propagation?
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