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Originally posted by somerandomuser
Got Deepthought's view on this:
From Deepthought:
Very, very close guys. The E-field that propagates along the axon is not a group phenomenom. The influx of ions changes the potential of the cell's membrane. So, this E-field is produced by the membrane itself, as such, it is a time-varying field for the purpose of Maxwell's equations.
Hope this helps,
Looks like we were both off a bit here.
Originally posted by somerandomuser
Looks like you are copying the posts for offline editing.
Originally posted by Bedlam
I dunno, I'm pretty sure it is. You most certainly get time-varying fields transverse to the axon, that's what the ion channels and pumps are for. However, once the depolarized volume is in the middle of the axon, the actual potential difference between the volume and the axon ends is the same no matter where the volume is in the length of the axon. I'd concede a boundary issue as the volume forms at one end. But once you have the depolarized area in place, the actual e-fields between that area, wherever it is, and the ends of the axon are relatively stable. Once it reaches the far end you end up with another boundary transition. So I'll give you two impulse functions at the beginning and end. Everything else is either ion channels opening in front or ion pumps spinning away in the back. You'll get a different rate of change at the two edges.
It's even weirder with saltatory conduction. Leaving that alone for now.
Thus, the membrane potential is physically located only in the immediate vicinity of the membrane. It is the separation of these charges across the membrane that is the basis of the membrane voltage.
Originally posted by Bedlam
Originally posted by somerandomuser
Looks like you are copying the posts for offline editing.
If you don't, the ATS demons will wait for you to post a magnum opus, then eat it.
ps sayonara for tonight. Since you're eating up all my play time, go figure out the nature of optically triggered exothermic reactions in carbon nanotubes (and probably graphene). I need to understand the mechanism well enough to fake a grant paper.
I just can't tell you why. Think of it as service to God, Country, and the DOE. (flag waving in background, cue Lee Greenwood singing "God Bless the USA")edit on 19-2-2012 by Bedlam because: (no reason given)
Originally posted by somerandomuser
So, the membrane potential is a time-varying E-field, otherwise there would be no membrane voltage.
Originally posted by somerandomuser
I'll get right on it...if you cut me in.
Originally posted by Bedlam
The action potential is what I'm saying is not a real charge motion. It's a group phenomenon caused by the membrane changes.
An electric field that changes with time, such as due to the motion of charged particles in the field, influences the local magnetic field. That is, the electric and magnetic fields are not completely separate phenomena; what one observer perceives as an electric field, another observer in a different frame of reference perceives as a mixture of electric and magnetic fields.
Originally posted by Bedlam
The ion flow down the axon is always one direction and doesn't alternate.
Originally posted by Bedlam
Originally posted by somerandomuser
I'll get right on it...if you cut me in.
If I can get DOE to buy off on the research grant, you might meet your first real MIBs and have an ad-hoc security clearance experience, unless we can find some way to hide the money transfer.
Originally posted by somerandomuser
But the action potential is the membrane voltage in motion, or an E-field in motion.
Think of a battery, you could claim the voltage in a circuit is the result of a group phenomenon at the terminals. So, as it is an E-field in motion, the following applies:
True, but the action potentional itself is an E-field changing from a negative state to a positive state. That's an alternating current.
Originally posted by somerandomuser
Originally posted by Bedlam
Originally posted by somerandomuser
I'll get right on it...if you cut me in.
If I can get DOE to buy off on the research grant, you might meet your first real MIBs and have an ad-hoc security clearance experience, unless we can find some way to hide the money transfer.
Ok, my first idea would be a modified form of the Wigner effect. Use a laser to knock out the atoms and build a displacement cascade. In theory, this should work. You could do a study on optimal firing patterns and interstitial arrangements.
I'm sure its good enough for a research grant.
Originally posted by Bedlam
No, the membrane depolarization is the e-field in motion.
In biology, depolarization is a change in a cell's membrane potential, making it more positive, or less negative.
In physiology, an action potential is a short-lasting event in which the electrical membrane potential of a cell rapidly rises and falls, following a consistent trajectory...
...Synaptic inputs to a neuron cause the membrane to depolarize or hyperpolarize; that is, they cause the membrane potential to rise or fall. Action potentials are triggered when enough depolarization accumulates to bring the membrane potential up to threshold.
Originally posted by Bedlam
It's not the same. It's more like one of those chasers around a movie marquee. It looks like a blob of light is moving around the periphery but it's just individual lamps in the chain turning on and off, nothing's really in motion.
Originally posted by Bedlam
But that field is changing across the membrane perpendicularly from inside the axon lumen to outside. I agree that component IS composed of moving charges. But the action potential propagating down the axon is like a movie chaser or people doing the wave at the stadium - it's not a charge in motion. It's a discharged bit of axonal goo whose location changes in time, but not due to something charged moving down the length of the axon, it's due to charges moving in and out of the axon wall just ahead and just behind of the current location of the depolarized spot.
Originally posted by Bedlam
Heck, for all of me it might be what's happening.
Transmembrane potential generated by a magnetically induced transverse electric field in a cylindrical axonal model.
During the electrical stimulation of a uniform, long, and straight nerve axon, the electric field oriented parallel to the axon has been widely accepted as the major field component that activates the axon. Recent experimental evidence has shown that the electric field oriented transverse to the axon is also sufficient to activate the axon, by inducing a transmembrane potential within the axon. The transverse field can be generated by a time-varying magnetic field via electromagnetic induction. The aim of this study was to investigate the factors that influence the transmembrane potential induced by a transverse field during magnetic stimulation. Using an unmyelinated axon model, we have provided an analytic expression for the transmembrane potential under spatially uniform, time-varying magnetic stimulation. Polarization of the axon was dependent on the properties of the magnetic field (i.e., orientation to the axon, magnitude, and frequency). Polarization of the axon was also dependent on its own geometrical (i.e., radius of the axon and thickness of the membrane) and electrical properties (i.e., conductivities and dielectric permittivities). Therefore, this article provides evidence that aside from optimal coil design, tissue properties may also play an important role in determining the efficacy of axonal activation under magnetic stimulation. The mathematical basis of this conclusion was discussed. The analytic solution can potentially be used to modify the activation function in current cable equations describing magnetic stimulation.
www.ncbi.nlm.nih.gov...
Originally posted by somerandomuser
So, an action potential is just the E-field reaching a threshold. It is still an E-field in motion.
An E-field does not require a charge in motion, in the sense you are referring to it. As I said above, the depolarisation causes an E-field to form, the action potential is triggered and that E-field is moved along the axon.
If this were not the case. we would observe the action potential as a progressive series of pulses running the length of the axon, as the gaps between the gates would cause the potential to change.
Originally posted by somerandomuser
Looks like there are two mechanisms.
The eight-watt ELF signal radiates from the dual-site system... (later) ...the Naval transmitter facility can bring as many as three Cummins diesel 1,000 kilowatt three phase power generators online to supply up to three million watts of power for the site. (The three million watts of power is an adjunct to three million more it took from the power grid, IIRC, and yet they get only eight watts out with a huge antenna compared to 1cm, and 6MW of transmitter input power, why? Because radiating ELF is crappily inefficient even when you work at it...Tom)
The submarines can receive ELF messages but they cannot transmit ELF signals because of the large power requirements, the large transmitter size, and the large antenna required to transmit ELF.
Originally posted by Bedlam
I get the impression we're talking around each other instead of communicating. I can't talk without a white board in front of me to do sketches. Not sure if it means I'm verbally challenged or mainly visual when I think.
From Deepthought:
I use MS paint a lot.
I do get his point. In a strict interpretation, depolarization is the change of potential, whereas an action potential describes the entire mechanism of the propagation when a certain threshold is reached.
Originally posted by Bedlam[
Ah, but the e-field longitudinal to the axon doesn't change - not once the depolarized area forms and starts to propagate and you get away from that damned boundary condition...
...You actually do. Good observation! It's not so obvious in non-myelinated axons, because the ion channels/pumps are comparatively dense and fairly evenly scattered. But when you've got nodal axons, you see the action potential area jump in discrete little hops. Go look up saltatory conduction. Several posts in the thread I've said something like 'things get weird with myelinated axons due to saltatory conduction, I'm going to ignore it for now', and that's what I was talking about.
From Deepthought:
I am not opposed to this. If the exact mechanism was simple, then everybody would be doing it. We are also moving from classical viewpoints, to quantum theory at this stage. I may have found an explanation that fits with Bedlam's viewpoint and may explain why ELF fields can control firing patterns.
Modeling the effect of an external electric field on the velocity of spike propagation in a nerve fiber
John M. Myers
Gordon McKay Laboratory, Harvard University, Cambridge, Massachusetts 02138
Received 21 April 1999; published in the issue dated November 1999
The effect of an externally generated electric field on the propagation of action potentials is modeled, assuming the Hodgkin-Huxley equation for the voltage-dependent conductance of the membrane of a nerve fiber. With some simplifying assumptions, this conductance together with Maxwell’s equations leads to the Hodgkin-Huxley differential equations for propagation, modified by a term proportional to the gradient of the externally generated electric field component along the nerve fiber. Computer solution of these equations shows the influence of an electric field gradient on propagation velocity. When the electric field oscillates, voltage spikes starting later along a given axon advance or lag relative to earlier spikes, so the time between spikes at the receiving end differs from the time between spike originations. The amount that a low-frequency electric field modulates pulse timing at the end of a fiber relative to that at the beginning is estimated under several conditions.
pre.aps.org...
Originally posted by Bedlam
Here's another thing I suddenly noticed hadn't come up from your end, although I sort of brushed it, and that's the whole near field/far field propagating or not issue as far as your signal goes...
Originally posted by Bedlam
Another thing to consider, and I still haven't gotten past the first one or two OP articles, is that you can't get better resolution of emitting sources less than about a wavelength - in this case a wavelength of about 750km - so if your method of mind reading involves actually knowing where in someone's head that neuron was - or separating out any two sources on, say, a complete hemisphere of the world from space, then you are going to have some issues. ELF is big and mushy, and you can't localize it because of resolution limits.