Physicists challenge notion of electric nerve impulses; say sound more likely

March 7, 2007 |

Danish scientists challenge the accepted scientific views of how nerves function and of how anesthetics work. Their research suggests that action of nerves is based on sound pulses and that anesthetics inhibit their transmission.

Every medical and biological textbook says that nerves function by sending electrical impulses along their length. “But for us as physicists, this cannot be the explanation. 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,” says associate professor Thomas Heimburg from the Niels Bohr Institute at Copenhagen University. He received his Ph.D. from the Max Planck Institute in Göttingen, Germany, where biologists and physicists often work together – at most institutions these disciplines are worlds apart. Thomas Heimburg is an expert in biophysics, and when he came to Copenhagen, he met professor Andrew D. Jackson, who is an expert in theoretical physics. They decided to work together in order to study the basic mechanisms which govern the way nerves work.

Physics explains biology

Nerves are ‘wrapped’ in a membrane composed of lipids and proteins. According to the traditional explanation of molecular biology, 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. It has taken many years to understand this complicated process, and a number of the scientists involved in the task have been awarded the Nobel Prize for their efforts. But – according to the physicists – the fact that the nerve pulse does not produce heat contradicts the molecular biological theory of an electrical impulse produced by chemical processes. Instead, nerve pulses can be explained much more simply as a mechanical pulse according to the two physicists. And such a pulse could be sound. Normally, sound propagates as a wave that spreads out and becomes weaker and weaker. If, however, the medium in which the sound propagates has the right properties, it is possible to create localized sound pulses, known as “solitons”, which propagate without spreading and without changing their shape or losing their strength.

The membrane of the nerve is composed of lipids, a material that is similar to olive oil. This material can change its state from liquid to solid with temperature. The freezing point of water can be lowered by the addition of salt. Likewise, molecules that dissolve in membranes can lower the freezing point of membranes. The scientists found that the nerve membrane has a freezing point, which is precisely suited to the propagation of these concentrated sound pulses. Their theoretical calculations lead them to the same conclusion: Nerve pulses are sound pulses.

Anesthetized by sound

How can one anesthetize a nerve so that feel ceases and it is possible to operate on a patient without pain? It has been known for more than 100 years that substances like ether, laughing gas, chloroform, procaine and the noble gas xenon can serve as anesthetics. The molecules of these substances have very different sizes and chemical properties, but experience shows that their doses are strictly determined by their solubility in olive oil. Current expertise is so advanced that it is possible to calculate precisely how much of a given material is required for the patient. In spite of this, no one knows precisely how anesthetics work. How are the nerves “turned off”? Starting from their theory that nerve signals are sound pulses, Thomas Heimburg and Andrew D.

Jackson turned their attention to anesthesia. The chemical properties of anesthetics are all so different, but their effects are all the same – curious!

But the curious turned out to be simple. If a nerve is to be able to transport sound pulses and send signals along the nerve, its membrane must have the property that its melting point is sufficiently close to body temperature and responds appropriately to changes in pressure. The effect of anesthetics is simply to change the melting point – and when the melting point has been changed, sound pulses cannot propagate. The nerve is put on stand-by, and neither nerve pulses nor sensations are transmitted. The patient is anesthetized and feels nothing.

From University of Coppenhagen

39 Responses to Physicists challenge notion of electric nerve impulses; say sound more likely

  1. Dave Majetich November 4, 2012 at 9:17 am #

    If the nervous system is based on sound, it almost makes sense that music and rhythm can effect the body in such a way that it does.

  2. Tabitha February 25, 2012 at 10:20 am #



  3. Anonymous November 14, 2010 at 7:30 pm #

    not at all.if no heat is generated by the current flow, then this violates the laws of thermodynamics. on the other hand, this theory actually supports the Hodgkins-Huxley theory of nerve impulses by accounting for the lack of heat created by the current flow. is it also really that far fetched to say that the body has redundant mechanisms for ensuring that these all important signals reach their targets?

  4. Anonymous November 14, 2010 at 7:23 pm #

    because we can’t hear that particular wavelength. in fact we cant here most sounds. just because we cant here it doesn’t mean its not sound. and this is sound through a lipid medium, not through air. and how would you electronically measure the propagation of a sound wave through such a fragile two dimensional layer without disturbing it?

  5. Swang November 4, 2010 at 1:33 pm #

    Great response! As a high school science teacher, I completely agree!

  6. Jon Loldrup August 12, 2010 at 1:02 pm #

    btw: it doesn’t react in the way that it activates muscles, sot maybe it’s not the same thing.

  7. Jon Loldrup August 12, 2010 at 8:16 am #

    Pianos can have an effect. I have a knee that reacts to vibrations from music. Yeah, it’s super weird. No diagnosis by the way.

  8. Big Lifted Trucks July 19, 2010 at 4:06 am #

    IF electricity is not controlling the muscles that what is? and why a patient with a heart attack is given electrical shock to his heart to make it beat again, hope this explains the electricity in the body….

  9. wesley miller June 15, 2010 at 6:38 am #

    maybe all energys such as electricity, sound, light, and the rest of it all come down to a single energy.

    on here people have said.. “if nerve are controlled by electricity wouldnt there be a cure for Reflex Sympathetic Dystrophy”.. this would rely on nervs being completley electrical. OR things like “Hearing implants are designed to use electrical impulses to allow subjects to crank up amplification of sounds”

    Einstien once said “A man should look for what is, and not for what he thinks should be.” and being the most famous man for his inventions and discouverys i believe we should take a leaf out of his book and look, not think, outside the box.

    tv’s / radios DO NOT simply SHOW electricity produces sound.. but what they do SHOW is that electricity is COMPATIBLE with sound. also frequency waves SHOW electicity is compatible with sound (FREQUENCY). now you may be thinkin what i have been thinkin, then that would mean that sound would have to be able to convert to electricity.. YES IT CAN.

    Electro-mechanical microphones use a small diaphram attached to a coil of wires suspended in a magnetic field. When the vibrations in the air cause cause the diaphram to vibrate, the movement of the coil of wire in the magnetic field generates a small electric current.

    i believe these two FACTS should show electricity doesnt just generate sound, and sound doesnt just generate electricity. what it does show is that they can also COME AS A PAIR, can be produced at the same time and also BY THE SAME MECHANICAL DEVICES.

    basically, it could either be we use sound and electricity at the same time in our nerves. or it could mean that we simply use neither, we use a seperate energy that we do not yet know, and the results we are picking up on (telling us it is either sound or electricity) could be the waste products emitting through sound and electricity charactoristics. not actualy sound or electricity itself.

    think of it as a Tree.. we can not see the routes of a tree because they are burried (in this case the roots being the energy we do not yet know that produces sound and electricity waste.) now what we do know is it gives us apples, as many apples as we need.. (apples being sound and electricity.) still we have not yet dug any deeper to relise that the apples (sound and electricity) would not be there with out the foundations of the ROOTS (the new energy) being in the ground where we can not see it.

  10. Anonymous March 11, 2009 at 6:30 am #

    I read recently that the purpose of the appendix is to harbour desired endogenous bacteria so as to be able to re-seed the colon when necessary

  11. Anonymous January 29, 2009 at 7:01 am #

    Another example would of course be the crystal glass breaking under harmonic resonance….frequency…

  12. Anonymous January 29, 2009 at 6:56 am #

    Perhaps you need a different type of “piano” to generate a sound that resonates harmonically with the frog’s leg. Harmonic frequencies tuned to resonate based on natural frequencies…the sweet spot…eg.

  13. Anonymous January 20, 2009 at 4:13 pm #

    of course it’s a reason for many surgeries as it gets inflammed, but tere’s a reason for existence of every human part.For example you can’t cut out the appendix from a very small child(don’t remember exactly the age)as the the digestive tract microflora develops there and a chilld’s digestion would be severly impaired(if not impossible)if he had appendectomia in an early age.The same is with thymus-it exists until around 12 years of age, later disappears.

  14. Anonymous October 2, 2008 at 2:23 pm #

    Actually, I meant that last post as a response to you. I actually expect that you would understand the principles that govern sound wave propagation.

  15. Anonymous October 2, 2008 at 2:20 pm #

    Complicated stuff naturally generates mis-understanding, I think.

    First; if sound waves are being used in the nerves, they’re probably only susceptible to a certain specific frequency.

    Second; sound can be insulated in much the same way as light is insulated in a fiber-optic cable. It refracts/bends when it passes from one medium to another in much the same way as light does.

    Under the electrical nerve theory, we don’t expect radio waves to set our nerves off, so under sound/mechanical wave theory, we shouldn’t expect sound to set our nerves off either.

  16. NeuroJoe March 11, 2008 at 8:05 am #

    “Yes, sound is a pressure wave that propagates in all directions, most of the time. A soliton is a pressure wave that does not change shape or intensity as it moves. This is not a theory, it is a proven phenomena found in nature. Solitons also exist in light waves and even water (some types of tidal bore). Basically, the shape of the wave causes it’s energy to be funneled back into itself and not dispersed.”

    Science can’t *prove* phenomena. It’s used as a tool to build hypotheses into theories, which are subject to further testing. In this way we can provide evidence for how natural processes may work, but we can never be certain enough to call it “proof”. There always may be more information generated in the future upon further testing which disproves our theory.

  17. cyberbian January 12, 2008 at 11:53 pm #

    Dont’cha just love it!

    Nature could not possibly have found a way to optimize using several variables for transmission!

    And medical patients couldn’t possibly have multiple issues at the same time.

    No, No, far to inconvenient!

  18. Anonymous December 13, 2007 at 1:50 am #

    Being a physics student I am surprised by some of the replies to this article. For instance, Electrical Engineers should talk about electricity and not sound propagation.

    Yes, sound is a pressure wave that propagates in all directions, most of the time. A soliton is a pressure wave that does not change shape or intensity as it moves. This is not a theory, it is a proven phenomena found in nature. Solitons also exist in light waves and even water (some types of tidal bore). Basically, the shape of the wave causes it’s energy to be funneled back into itself and not dispersed.

    Sound comes in different frequencies, which we hear as pitch. For instance, some voices are higher or lower depending on faster or slower frequency. Just as our eyes can only see certain wavelengths of light and can’t see ultraviolet or infrared light waves, our ears can only pick up certain frequencies of sound. If there was a sound pulse from our nerves it could be outside this frequency and the amplitude so small (we’re talking a scale of a nanometer) that no, we cannot hear our nerves.

    This theory is misquoted a bit and if you read the paper that is linked in a comment above, it accepts that heat is produced and that electrical pulses are present. It simply says that electrical pulses cannot fully explain the observed changes in the volume and viscosity of the nerve during impulse. The theory says that the observed electrical pulse could be a byproduct of the mechanical motion of the nerve, and the myelin sheath contributes to heat release which is then almost perfect reabsorbed (which is the contradiction with thermodynamics).

    Yes, the heart emits electrical impulses, but it moves too. You can attach an electrode to your arm and make it move, but screaming at it does nothing. I would infer that if the electrical signal were a byproduct of the mechanical motion, that such a signal could also cause mechanical motion in the nerve and thus move the arm. The nerve fibers that the sound wave moves through would have to be insulated (although not “perfect acoustic insulators”) and only specific waves (solitons) would travel undisturbed. Otherwise, we’d all be flopping around uncontrollably from the sounds around us.

  19. Anonymous November 30, 2007 at 6:27 pm #

    Here is my two cents worth being that i am an electronics engineer that designs professional audio products every day.
    If the nerve impulses were sound waves they would propagate everywhere throughout the body due to some bloody obvious things.. Surrounding each cell is a given quantity of water and as we all know it happens to be a very efficient conductor of sound. Secondly any sound waves would happily radiate in all directions when they are reflected of any body that lies in its path. so for this theory to be worth a damn it would rely on the fact that the sheath is a PERFECT acoustic insulator and that the universe created a really funky anomaly for your theory to work.
    I suppose that they will tell us that Phlogistin is responsible….
    Hey try a MAGNETIC wave, it makes more sense and fits the model a touch better especially when it comes to thermodynamics.

  20. Anonymous October 29, 2007 at 1:47 am #

    I find the idea very interesting, however I wonder how they would explain our current exploitations of the human nervous system which rely on the presence of electrical impulses.

    Hearing implants are designed to use electrical impulses to allow subjects to crank up amplification the same way you turn up the volume on a TV. Nerves have also been exploited in the brain so much as to allow for the replacement of eyes ( and elsewhere as in the addition of a bionic arm ( In any case, electrical devices are being used by subjects almost as intuitively as the organic parts they’re meant to replace, which suggests that they are functioning in a similar way.

    On the one hand, the human nervous system may adapt somewhat to the devices, but if it only functioned by way of mechanical waves, why would it provide electrical impulses just out of the blue?

    If it weren’t for these innovations, I would find their heat discovery fairly convincing. As it is, it seems to be yet another unexplained mystery of the life. Still, I’d love to hear more about the sound theory. Maybe they actually use a combination of sound and electricity. Maybe it’s much more complex (or simple) than we ever imagined.

  21. Anonymous October 18, 2007 at 6:23 pm #

    I love the new theory, but of course I am always up for popular beliefs being overturned. Besides, if nerves really were determined by electricity wouldn’t they have been able to find a cure for RSD (Reflex Sympathetic Dystrophy) A progressive disease that attacks the nervous system giving the patient suffering with it sensations of burning in the hands feet and legs? Come on, open up your minds, next you people are going to cry the global warming is a crock full of beans as well!

  22. Anonymous September 22, 2007 at 11:48 am #

    I began to read this article with interest until I came to the statement “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,” says associate professor Thomas Heimburg…”. At this point I sensed a disconnect between the quotation and the actual content of the paper. Its authors are well aware of the heat production associated with a nerve impulse, a phenomenon that has been known for decades. For example, they cite the the following article:
    Abbott, B. C.; Hill, A. V.; Howarth, J. V. The Positive and Negative Heat Production Associated with a Nerve Impulse. Proceedings of the Royal Society of London. Series B, Biological Sciences, Volume 148, Issue 931, pp. 149-187, 1958.
    So I am puzzled by the quotation given in the news release. The authors of the study have proposed a new mechanism for nerve impulse propagation in their attempt to overcome some of their perceived shortcomings in the Hodgkin-Huxley theory, which has a huge literature in its support. Certainly any theory is open to challenge, but Heimburg and his collaborators have a heavy burden of proof which (at least by my reading of their paper), they have not met, nor have others with various competing theories. It will be interesting to see how this plays out.

  23. Anonymous July 17, 2007 at 6:47 am #

    This theory seems to contradicts the entire structure of the nerve. Because in most cases with the human body everything is there for a reason. (with exception to the appendix) Nerves are equipped with a myelin sheath to help aid in the quickening of impulses sent between nerves. It aids as an insulator for the electrical impulses, which explains why impulses are slower on un-myelinated nerve cells. So with this theory it would make a major part of the nerve cell seemingly useless and for billions of cells in our body to have a completely useless feature seems overly far fetched.

  24. Anonymous July 12, 2007 at 9:14 pm #

    Relatively loud sounds are audible in air. These are much much smaller amplitude and are contained waves in nerve fibers. Calling them sound waves just means that they’re a certain kind of longitudinal wave in a medium. That’s very different from them being macroscopic waves in air that our ears are sensitive to.

  25. Dr.Bobyjeet Goswami June 16, 2007 at 9:13 pm #

    What ab the various NT and tranmission thru the synapses?

  26. John Hammond June 13, 2007 at 4:35 pm #

    To dismiss out of hand without examination is the reason the earth was flat for so many years. The “Sound as a media for nerve transmission” theory could provide the solution as to how Acupuncture works

  27. Anonymous March 27, 2007 at 1:39 pm #

    The entire idea of science is to look at a process, come up with a hypothesis that could explain it, and to then test the hypothesis via experimentation.

    these scientists have come up with a hyposthesis and presumably will try to test it. it is an interesting idea, and understanding it requires knowledge of the biochemistry and biophysics of membranes, and the physics of sound in microscopic conditions. it may be hard to do the experiments. it may be impossible to produce evidence. but if they can accumulate data to support their hyposthesis, the burden of evidence will lead other scientists to use the idea as a reasonable explanation.

    the number of people who laughed at this hypothesis in the preceeding comments is concerning. to ridicule a new idea is not part of the scientific process. it is at least bad playground behavior. worse, it turns knowledge into faith, an unassailable wall that stifles intellectual curiosity and creative thinking. history is filled with examples of how badly that turns out. if you don’t think an idea is correct you should do the experiments to disprove it, or wait for the proponent to give evidence. in fact, you should do the same thing if you believe in the idea. it is the only way that science can move forward. remember einstein and quantum mechanics. the burder of evidence gives us an approximation of the truth, and every scientific idea is testable, by definition.

  28. Anonymous March 20, 2007 at 1:37 pm #

    dogs can pick all many sounds that we cant. it depends on how loud the sound is

  29. Anonymous March 19, 2007 at 2:26 pm #

    attach a frogs leg to a battery and it will twich. attach a frogs leg to a piano and it will do nothing.

  30. Anonymous March 7, 2007 at 5:13 pm #

    There was a soliton theory of muscle contraction put forth about 15 years ago and that never got anywhere, either. Maybe it was soliton sound wave that produced the ripping sound of my hernia in the gym recently… ;)

  31. Anonymous March 7, 2007 at 4:58 pm #

    “The scientists found that the nerve membrane has a freezing point, which is precisely suited to the propagation of these concentrated sound pulses.” Proposing that the lipid membrane of the neuron and the seperate cell providing myelination are “freezing” to propagate sound waves needs some EVIDENCE.

  32. Anonymous March 7, 2007 at 4:29 pm #

    People criticising this theory might do well to read the paper in which they spell it out.

  33. Anonymous March 7, 2007 at 12:28 pm #

    Hmm. To put it in a simple way…How does one spell “Urban Legend”?

    I applaud you for the effort. But sometimes I have to shake my head in disbelief as to HOW brilliant minds can put all that mental super-goo to waste…?

    Really. One factor of science that is often omitted (I’ve been guilty of it), is relevance…nerve impulses, sound??? Come on…really.

  34. Anonymous March 7, 2007 at 11:07 am #

    Sound is audible. Why can’t we hear all the noise our neurons are making?

  35. Anonymous March 8, 2007 at 1:52 pm #

    The transducing of electrical to acoustic waves via solitons is not something new and was discussed in extensive detail by Frank Barr, who pioneered (alone) the concept of neuromelanin and its effect on information propagation in the nervous system.

    Barr FE. Melanin: the organizing molecule.Med Hypotheses. 1983 May;11(1):1-139.
    The hypothesis is advanced that (neuro)melanin (in conjunction with other pigment molecules such as the isopentenoids) functions as the major organizational molecule in living systems. Melanin is depicted as an organizational “trigger” capable of using established properties such as photon-(electron)-phonon conversions, free radical-redox mechanisms, ion exchange mechanisms, and semiconductive switching capabilities to direct energy to strategic molecular systems and sensitive hierarchies of protein enzyme cascades. Melanin is held capable of regulating a wide range of molecular interactions and metabolic processes primarily through its effective control of diverse covalent modifications. To support the hypothesis, established and proposed properties of melanin are reviewed (including the possibility that (neuro)melanin is capable of self-synthesis). Two “melanocentric systems”–key molecular systems in which melanin plays a central if not controlling role–are examined: 1) the melanin-purine-pteridine (covalent modification) system and 2) the APUD (or diffuse neuroendocrine) system. Melanin’s role in embryological organization and tissue repair/regeneration via sustained or direct current is considered in addition to its possible control of the major homeostatic regulatory systems–autonomic, neuroendocrine, and immunological.

  36. Anonymous March 7, 2007 at 10:30 am #

    Sound waves – they can’t be serious?

  37. Anonymous March 8, 2007 at 4:36 pm #

    Freezing is a state change from liquid to a more solid state. Depending on the additional items in an oil solution, it can be very high temperatures where this state change happens. The fulltext article (linked elsewhere in this chain of comments) spells things out in rather more detail.

  38. Anonymous March 7, 2007 at 9:33 am #

    This hypothesis has been around for decades and the study of it has failed to generate enough positive data to lead us to believe that sound waves instead of ion flux is how impulses are generated. Just because we don’t know yet how many anesthetics work at the molecular level doesn’t mean that they have to work by inhibting sound waves. We don’t know how gravity works either but that doesn’t mean that current theories of gravity are worthless, it just means we don’t have the right foundation of knowledge or the right tools to understand it yet.

  39. Anonymous March 7, 2007 at 8:40 am #

    I don’t know what this guy is up to, but we know exactly how nerves work. Do you have a link to the actual article?

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