Danish scientists argue that nerves use sound, not electricity

[neutrino_cannon]

http://www.cbc.ca/technology/story/2007/03/09/science-nervessound-20070309.html



I do not claim to know anything about neuroscience, but wouldn't the fact that at least rudimentary machine/brain interfaces have been constructed using electrodes connected to a computer indicate contrary to this claim?

I would also mumble something about MRI scanners, but I don't understand entirely how those work.

And if it's sound, why are electrical shocks dangerous?

[Ziggurat]

I do not claim to know anything about neuroscience, but wouldn't the fact that at least rudimentary machine/brain interfaces have been constructed using electrodes connected to a computer indicate contrary to this claim?

Sounds pretty unlikely to me. Among other things, there's no indication in the article that they've figured out a mechanism for initiation of such sound waves from one end of the nerve or reception of that soundwave at the other end to release neurotrasmitters (which we know transmit between nerves). Nor do they explain what the electrolyte channels observed in nerves are doing if they aren't part of transmitting an electric signal. They also claim that anaesthetics might work by changing the membrane melt temperature. But that seems unlikely considering the success we've had analyzing anaesthetics and other psychoactive drugs on the basis of neurotrasmitters and receptors. It's just wild speculation, as far as I can tell.

[Orangutan]

http://img.photobucket.com/albums/v56/Orangutan/HEIMBURG-Thomas40-4.jpg
Thomas Heimburg
Niels Bohr Institute, Blegdamsvej 17, Room Kc9
2100 Copenhagen Ø - Denmark
Tel: +45 -3532 5389, FAX: +45-353 25016
mail: theimbu@nbi.dk

"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."

special kind of sound pulse or "soliton" that can propagate without spreading or losing strength

Thomas Heimburg, an expert in biophysics who received his PhD from the Max Planck Institute in Goettingen, is an associate professor at the university's Niels Bohr Institute.

That's some pretty impressive credentials, And yet that goes against everything we know!

Has this guy never put a 9 Volt battery on his tongue?

Edit:
There's a wiki page on this int's not new its about 2 years old.
http://en.wikipedia.org/wiki/Soliton_model

[CFLarsen]

And if it's sound, why are electrical shocks dangerous?

If you are going to take a piss in the wild, be sure there isn't an electric fence around.

[ponderingturtle]

http://www.cbc.ca/technology/story/2007/03/09/science-nervessound-20070309.html



I do not claim to know anything about neuroscience, but wouldn't the fact that at least rudimentary machine/brain interfaces have been constructed using electrodes connected to a computer indicate contrary to this claim?

I would also mumble something about MRI scanners, but I don't understand entirely how those work.

And if it's sound, why are electrical shocks dangerous?

That is the wrong question. Electricity could still burn you and such from thermal effects. It is why does electric shocks cause muscle contraction and why to electrical sensors detect these potentials.

It would also seem to suggest that a pace maker couldn't work.

[ImaginalDisc]

That is the wrong question. Electricity could still burn you and such from thermal effects. It is why does electric shocks cause muscle contraction and why to electrical sensors detect these potentials.

It would also seem to suggest that a pace maker couldn't work.

And why do sharks reliably exploit this to hunt prey, using a sense that becomes more effective when the prey is moving vigorously?

[dakotajudo]

Nor do they explain what the electrolyte channels observed in nerves are doing if they aren't part of transmitting an electric signal.
I think they're working from the perspective that the Hodgkin-Huxley model is not sufficient to explain observed thermodynamics of action potentials; I'm not sure they need to, at this point, explain membrane channels.

They also claim that anaesthetics might work by changing the membrane melt temperature. But that seems unlikely considering the success we've had analyzing anaesthetics and other psychoactive drugs on the basis of neurotrasmitters and receptors.

The work addresses the actions of general anaesthetics - organic solvents like alcohol. Is there receptor model for ethanol?

That anaesthetics might work by altering membrane fluidity isn't far fetched at all. This time of year, I start thinking about planting my garden; in particular, tomatos and peppers.

If you transplant greenhouse tomatos directly into the garden, in the spring, you'll most likely get photodamaged tomatos. The plants are aclimated to 70F temps; aclimation that includes adjusting membrane lipids to have optimal fluidity at that temp.

Put these plants in the sun at 60F, their membrane-bound photosynthetic apparatus won't function properly, and they'll get, essentially, sun-burned. Light-activated electrons won't be carried across the membranes properly.

Maybe this is a long-winded explanation (I'm more comfortable with plant physiology to explain this point); but it isn't difficult to think that membrane melting point can affect nerve function.

Not that I agree with the authors' claims - I don't see any real reason to doubt the Hodgkin-Huxley model, and don't think the soliton model is needed to account for anaesthetics.

My understanding of the fluid mosaic model is that it's more mosaic than fluid - that is, cell membranes are more protein, with little for unbroken expanses of lipid bilayer. I'm not so sure a soliton could propagate far without being dispersed by intervening membrane proteins.

I did my M.A. work on action potentials in Mimosa; as I remember, there was some suggestion that these signals were transmitted via hydraulic signals, not ionic (I hate to use electrical, that oversimplifies the process). This seems to be along similar lines.

[skeptigirl]

If you are going to take a piss in the wild, be sure there isn't an electric fence around.
Didn't the Mythbusters show that was a myth?

[CFLarsen]

Didn't the Mythbusters show that was a myth?

Let's just say that, when you're a small kid, things have a different perspective.

[chance]

If it was sound, then how is that sound insulated from the solid/liquid that encapsulates it? sound travels through solid liquid and gas, you would need to have a sound ‘insulator’ (if such was even feasible) around every neural pathway.

[Ziggurat]

The work addresses the actions of general anaesthetics - organic solvents like alcohol. Is there receptor model for ethanol?

Seems like it:
http://www.ionchannels.org/showabstract.php?pmid=9670216

That anaesthetics might work by altering membrane fluidity isn't far fetched at all.

It is if you can't show that the membranes in question ever enter a solid phase in an actual organism, which as far as I know nobody has done. Because just changing the viscosity of the fluid doesn't cut it for what they're proposing: they need the membrane to enter an actual solid phase.

[neutrino_cannon]

Didn't the Mythbusters show that was a myth?

Not that it's anything approaching a reliable source, but my father swears up and down that when he was younger and more rambunctious he got a fellow to do just that.

[casebro]

Neuro-Electrical impulses push a calcium ion through a membrane. Is that push strictly electrical, or could you say the impulse physically pushes the c+? Lessee, the calcium ion is split off of some molecule, and the total volume of the molecule (without a c+) plus one c+ off the molecule, is bigger? There is conservation of mass, not conservation of volume. So, we explode a molecule, just like dynamite, wherein a reaction takes place that makes lots more volume. Shock wave to push that ole c+ through a membrane, comin right up!

Electrical tranmission down the wires, to the blasting cap, cap sets off the muscle explosion...

We've all heard of Nitro-Glycerine, and how it does good things for smooth muscles- good for chest, as well as penis's- it's the nitro that is used extensively for signaling in the body, the basis of Viagra...Kick it up a Notch, Ted!

[bjornart]

Didn't the Mythbusters show that was a myth?
No, they showed that peeing on the third rail is a myth, unless you do it kneeling down and leaning across the rail. The revisited the myth in episode 14 testing with an electrical fence, and Adam got... buzzed.

So if you're going to pee on anything electrical, maintain a safe distance.

[MortFurd]

Didn't the Mythbusters show that was a myth?
The catch is that pee isn't a continuous stream. It starts out that way, but separates into individual drops.

If you are standing up and the pee hits the electrical source near the ground, then you are pretty safe. If the pee hits the electrical source higher up, before the stream breaks down into droplets, you are due for a zap.

So, taking a leak on the subway third rail is pretty safe - but standing in front of an electric fence and peeing on the post could well cause you pain.

[ponderingturtle]

Neuro-Electrical impulses push a calcium ion through a membrane. Is that push strictly electrical, or could you say the impulse physically pushes the c+? Lessee, the calcium ion is split off of some molecule, and the total volume of the molecule (without a c+) plus one c+ off the molecule, is bigger? There is conservation of mass, not conservation of volume. So, we explode a molecule, just like dynamite, wherein a reaction takes place that makes lots more volume. Shock wave to push that ole c+ through a membrane, comin right up!

Electrical tranmission down the wires, to the blasting cap, cap sets off the muscle explosion...

We've all heard of Nitro-Glycerine, and how it does good things for smooth muscles- good for chest, as well as penis's- it's the nitro that is used extensively for signaling in the body, the basis of Viagra...Kick it up a Notch, Ted!
Nitro does not effect muscles, it is a strong vasodilator, so it makes all your blood vessels dilate. This improves blood flow to areas not getting enough. It also causes headaches.

[casebro]

Nitro does not effect muscles, it is a strong vasodilator, so it makes all your blood vessels dilate. This improves blood flow to areas not getting enough. It also causes headaches.

Arteries have multiple layers. One layer is smooth muscles. And how does Nitro dialate arteries? By relaxing those smooth muscles. Allowing more blood flow, letting those arteries throb. Makes heads throb. Also other parts that depend on blood flow.

[ponderingturtle]

Arteries have multiple layers. One layer is smooth muscles. And how does Nitro dialate arteries? By relaxing those smooth muscles. Allowing more blood flow, letting those arteries throb. Makes heads throb. Also other parts that depend on blood flow.

ANd that is why Viagra was originally developed as a heart medication. But I have never heard of any direct effects on cardiac muscle from nitro, just preventing and correcting ischemic issues

[Dancing David]

Just for starters nerves DON'T USE ELECTRICITY! There is no transmission of electrical energy they way there is in a conducting wire.

It is a biochemical impulse that travels through the nerve, not an electrical impulse like in a wire. It is based upon the sodium/calcium(?) and potasium channels opening and closing but the impulse is chemical in nature. The cell uses the osmotic pressure of the charged particles and there is a difference in electrical potential in the cell vs. extra cellular area, but the impulse is biochemical in nature and uses the electrical potential of the ions to 'charge' and 'discharge' the system. In some very weak ways it is like a battery but the impulse that travels along the nerve is chemical in nature.


http://psych.hanover.edu/KRANTZ/neural/actionpotential.html

When the sodium channels open during the depolarization (the red section of the action potential curve), the Na+ rushes in because both of the greater concentration of Na+ on the outside and the more positive voltage on the outside of the axon. When the Na+ channels close and the K+ channels open (the green section of the action potential curve), the K+ now leaves the axon due both to the greater concentration of K+ on the inside and the reversed voltage levels.
Thus, in many ways the action potential is not the movement of voltage or ions but the flow of these ion channels opening and closing moving down the axon. This movement of the ion channels explains why the action potential is slow relative to the normal flow of electricity. The normal flow electricity is the flow of electrons in an electrical field and electricity travels at the speed of light while these ion channels movment is considerably more slowly. These are mechanical movements and cannot move nearly at the speed of light.

[autumn1971]

Didn't the Mythbusters show that was a myth?


Yeah, like others have posted before, the Mythbusters only showed that a urine stream is not a great conductive apparatus. I can assure you that a male (the stream is a better approximation of a constant flow when near a penis than it is near a female urethral opening) urinating on a live wire near waist height results in loud cursing and grasping of genitals (the hopping about with pants around the ankles is just bonus amusement).

[ponderingturtle]

Just for starters nerves DON'T USE ELECTRICITY! There is no transmission of electrical energy they way there is in a conducting wire.

It is a biochemical impulse that travels through the nerve, not an electrical impulse like in a wire. It is based upon the sodium/calcium(?) and potasium channels opening and closing but the impulse is chemical in nature. The cell uses the osmotic pressure of the charged particles and there is a difference in electrical potential in the cell vs. extra cellular area, but the impulse is biochemical in nature and uses the electrical potential of the ions to 'charge' and 'discharge' the system. In some very weak ways it is like a battery but the impulse that travels along the nerve is chemical in nature.


http://psych.hanover.edu/KRANTZ/neural/actionpotential.html

I am not sure I think this is a significant difference. It seems like how electricity flows through electrolyte solutions instead of metals. Sure there are not the free floating electrons in the cells, they are not a conductive metal so you would not get that effect, but you can conduct an electric current through other things, like electrolyte solutions, and that generally results in things like electroplating and other chemical reactions and you are moving ions around not electrons.

See the pissing on a live wire part of this thread to see that electrolyte solutions can conduct effective currents.

[MortFurd]

I am not sure I think this is a significant difference. It seems like how electricity flows through electrolyte solutions instead of metals. Sure there are not the free floating electrons in the cells, they are not a conductive metal so you would not get that effect, but you can conduct an electric current through other things, like electrolyte solutions, and that generally results in things like electroplating and other chemical reactions and you are moving ions around not electrons.

See the pissing on a live wire part of this thread to see that electrolyte solutions can conduct effective currents.
There's quite a difference between the two.

Current flow (through metal or an electrolyte) involves moving the charge itself. That is to say electrons by themselves are moved.

The bichemical process in the nerves (as I understand it) involves charged atoms (ions) being moved. Imagine carrying a charged battery across the room to power a light as opposed to connecting wires to carry the current across the room to the light.

[dakotajudo]

Seems like it:
http://www.ionchannels.org/showabstract.php?pmid=9670216


I should have been more clear - is there a specific ethanol receptor binding site? More along these lines: http://www.pnas.org/cgi/content/full/103/22/8307


It is if you can't show that the membranes in question ever enter a solid phase in an actual organism, which as far as I know nobody has done. Because just changing the viscosity of the fluid doesn't cut it for what they're proposing: they need the membrane to enter an actual solid phase.
No, they don't need the membrane to enter a solid phase; no more than chilling injury requires a solid phase (that's why I used the analogy).

I'm not sure you can say that nobody's shown a solid membrane phase in living organism (well, solid for a lipid membrane, which isn't quite a solid phase, is it?). Some of the work towards the "lipid raft" hypothesis has shown local areas of ordered lipids, especially around receptor proteins. (http://www.pnas.org/cgi/content/full/100/26/15554 , for example). Obviously, you don't expect the entire membrane to enter a solid phase in living organisms (although there is some evidence of a gel phase in "dark" cells - but that may be mostly cytoplasm).

[ponderingturtle]

There's quite a difference between the two.

Current flow (through metal or an electrolyte) involves moving the charge itself. That is to say electrons by themselves are moved.

No it is the ions in an electrolyte. You do not have the unbound electrons in an electrolyte solution that you do in a metal. That is why you get things like electro platinging and such. You get some ions moving in only one dirrection so you get them all gathering at one side.

The bichemical process in the nerves (as I understand it) involves charged atoms (ions) being moved.

Just like in an electrolyte.

Imagine carrying a charged battery across the room to power a light as opposed to connecting wires to carry the current across the room to the light.

This is just wrong.

Edited to add link: link explaining current flow in electrolytes (http://www.newton.dep.anl.gov/askasci/gen01/gen01755.htm)

And ionic flow is just a form of electric current flow.

[dakotajudo]

Neuro-Electrical impulses push a calcium ion through a membrane. Is that push strictly electrical, or could you say the impulse physically pushes the c+? Lessee, the calcium ion is split off of some molecule, and the total volume of the molecule (without a c+) plus one c+ off the molecule, is bigger? There is conservation of mass, not conservation of volume. So, we explode a molecule, just like dynamite, wherein a reaction takes place that makes lots more volume. Shock wave to push that ole c+ through a membrane, comin right up!

You seem to be mixing a few things together.

Nerve action potentials are driven by Na/K channels; Ca (and it's a divalent cation - Ca++) channels are part of related events - vesicle fusion at the axon terminal which triggers the release of neurotransmitters, for example, or the opening of calcium channels in the sacroplasmic reticulum that couple excitation to contraction.

Not sure about Ca being split off some molecule - it's generally a free ion prior to the action potential event; inside the cytoplasm, it binds to something as a second messenger (calmodulin, troponin, etc). Chelators like EDTA that bind free Ca tend to mess up electrophysiological processes.

Volume changes are pretty minor (though, I think, detectable) - most of the ionic changes occur at or near the membane.

[dakotajudo]

Just like in an electrolyte.

Not just like an electrolyte. The action potential involves monovalent cations, not anions; the resting membrane potential is maintained pretty much by potassium flow (there is a little bit of sodium leakage, so RMP isn't exactly the potassium equilibrium potential).

There anions involved, but most, proteins and phosphate, don't move; they do contribute to the net negative charge inside the cell.

As I said above, potassium movement maintains the RMP. In this case, potassium moves out of the cell, along a chemical gradient. Since the inside of the cell is net negative, chloride also moves out, with the electrical gradient, until the chemical potential balances the electrical potential. So, anions and cations move in the same direction - not to opposite poles that would be required for electrolyte current.

It's confusing, because the establishment of the RMP is largely bulk movement of ions. The action potential involves only a small portion of the total concentration, and only the volume near the membrane.


Edited to add link: link explaining current flow in electrolytes (http://www.newton.dep.anl.gov/askasci/gen01/gen01755.htm)

You do realize that's a fourth-grade level explanation?


And ionic flow is just a form of electric current flow.
No, because you can have movement of cations, but no corresponding anionic movement (or vice-versa).

[casebro]

You seem to be mixing a few things together.

Nerve action potentials are driven by Na/K channels; Ca (and it's a divalent cation - Ca++) channels are part of related events - vesicle fusion at the axon terminal which triggers the release of neurotransmitters, for example, or the opening of calcium channels in the sacroplasmic reticulum that couple excitation to contraction.

Not sure about Ca being split off some molecule - it's generally a free ion prior to the action potential event; inside the cytoplasm, it binds to something as a second messenger (calmodulin, troponin, etc). Chelators like EDTA that bind free Ca tend to mess up electrophysiological processes.

Volume changes are pretty minor (though, I think, detectable) - most of the ionic changes occur at or near the membane.

Okay, so sub sodium or any metal for calcium. I wouldn't think there are many free metal ions floating around. Metals are highly reactive. So it must be usually bound to something- those proteins you mentioned? Splitting it off takes electircal energy. And, the splitting causes motion (define splitting?), the motion could cause a shock wave at the instance of splitting, hence the "ultrasonic signal".... in my pea brain. Oh the sonic booms are giving me a head ache...

[Overman]

Think how about how much you are hurting people next time you yell at them!

[Ziggurat]

No, they don't need the membrane to enter a solid phase;

If it's not in a solid phase, I don't see how they can possibly expect soliton excitations. If the membrane remains in the normal liquid phase, I can't see how any high-energy excitations can overcome damping effects (and they have to be high energy excitations because they must be well above thermal energies).

[ponderingturtle]

Not just like an electrolyte. The action potential involves monovalent cations, not anions; the resting membrane potential is maintained pretty much by potassium flow (there is a little bit of sodium leakage, so RMP isn't exactly the potassium equilibrium potential).

There anions involved, but most, proteins and phosphate, don't move; they do contribute to the net negative charge inside the cell.

As I said above, potassium movement maintains the RMP. In this case, potassium moves out of the cell, along a chemical gradient. Since the inside of the cell is net negative, chloride also moves out, with the electrical gradient, until the chemical potential balances the electrical potential. So, anions and cations move in the same direction - not to opposite poles that would be required for electrolyte current.

It's confusing, because the establishment of the RMP is largely bulk movement of ions. The action potential involves only a small portion of the total concentration, and only the volume near the membrane.

Ah. I knew that it would not work as a simple explanation as a current flow, as you need to re ballance the levels or you get some plating effect.


You do realize that's a fourth-grade level explanation?


And it seemed to be needed, as there was the supposted differences where that ions move in the cells while electrons move in an electrolyte. That is entirely wrong, and not a way to differeniate the cells reactions from an electrical signal.

No, because you can have movement of cations, but no corresponding anionic movement (or vice-versa).

And this is a much clearer answer as to the distictions than Mortfurd's talk about it being ions and not electrons so it is not a current flow.

[ponderingturtle]

Okay, so sub sodium or any metal for calcium. I wouldn't think there are many free metal ions floating around. Metals are highly reactive. So it must be usually bound to something- those proteins you mentioned? Splitting it off takes electircal energy. And, the splitting causes motion (define splitting?), the motion could cause a shock wave at the instance of splitting, hence the "ultrasonic signal".... in my pea brain. Oh the sonic booms are giving me a head ache...

You have sodium ions. They are not highly reactive as they are not metallic particles, but disassociated salts.

You want to see a lot of free metal ions floating around but some salt into water. The Na+ and CL- disassociate as a crystal and float around freely in the solution. They are only bound to something if they come out of solution, they ions hang around each other to avoid concentrations of electric charge, but are not bonded directly to anything.

[ingoa]

...snip...but standing in front of an electric fence and peeing on the post could well cause you pain.


Could?
Could?

Does!

Don't ask.... :eek:

[dakotajudo]

Okay, so sub sodium or any metal for calcium.
You can't do that, physiologically. Propogation of an action potential requires channels that are selective for Na or K only; and other processes require that Ca is a divalent cation, not monovalent like Na or K.

So it must be usually bound to something- those proteins you mentioned? Splitting it off takes electircal energy. Mostly, salt bonds, not covalent bonds. Covalent bonding would require electrical energy, but ionic bonds much more labile.


And it seemed to be needed, as there was the supposted differences where that ions move in the cells while electrons move in an electrolyte. That is entirely wrong, and not a way to differeniate the cells reactions from an electrical signal.

Well, there was this section:

5. There is a complication however, the water and / or certain of the ions
may undergo a chemical reaction to one or the other, or both of the electrodes.
You may not want to introduce this in the beginning but it does happen.

Isn't that how electroplating works? Dissolved ions accept an electron, can no longer stay in solution.

The chemical reactions implied are seen in the charge seperation associated with the light reactions of photosynthesis, and oxidative phosphorylation.

When bioelectricity is discussed, people usually refer to action potentials, but it seems to me that the electron transport chains are more like electrical current.


If it's not in a solid phase, I don't see how they can possibly expect soliton excitations. If the membrane remains in the normal liquid phase, I can't see how any high-energy excitations can overcome damping effects (and they have to be high energy excitations because they must be well above thermal energies).

Isn't that the point of the 2005 PNAS paper - that the expected temperature changes for soliton propagation are consistent with experimental results? It's not a bulk process in a three-dimensional solid, no more than the action potential itself.

Personally, I see no issue with solitons propagating *along* with the signal, but not as the signal itself. The 2007 paper, described in the OP, is more interesting for the implications w.r.t. the lipid raft hypothesis.