Saltatory Conduction: single AP or not?

somasimple

You affirm that a temporal signal (where time can't be stopped) and flowing in a wire/cable from an end to the other one may be discontinuous in t?

I'm rather pleased to see your constant affirmations ever contested by Science.
I must thank you, the model is less robust than before with your help.

granpa

I assume that somasimple is saying that the signal moves from one node to the next then stops at the node for a short delay before continuing on. I actually tend to agree with him here. the graph here:
http://www.pubmedcentral.nih.gov/pag...92&pageindex=8
seems to support this idea.
but I dont see what the big deal is. the signal is transported passively through the internode but the nodes themselves are active. so why not a delay? its 2 different mechanisms.

somasimple

granpa,
I said apparent .
It look like a traveling wave at nodes but it can't travel in such a tiny space.

granpa

apparent?
traveling wave at nodes?
cant travel in such a tiny space?

granpa

so its only an apparent delay? its still a traveling wave at the nodes? what do you mean 'cant travel in such a tiny space'?

somasimple

granpa;
a delay is a delay (it's a duration).
it is an apparent traveling wave.
Edit: That's why, in myelinated axons the soliton has no solution. Nodes are like little windows wher you can see only a little bit of an AP. You see an AP through a so little window that it appears as traveling but it doesn't.
The movie I provided show this. the blue regions are nodes where voltage grows ans decays at the same place but if we record (introducing a t variable) these variations you will obtain the shape of the AP (caution: the movie is just an example)

DaleSpam

Yes. And I have given a very simple specific example: H(x-ct). It is discontinuous at t=x/c since [tex]\lim_{t\to \frac{x}{c}^-} \, H(x-c t)\neq \lim_{t\to \frac{x}{c}^+} \,
H(x-c t)[/tex] and at x=tc since [tex]\lim_{x\to (c t)^-} \, H(x-c t)\neq \lim_{x\to (c t)^+} \, H(x-c t)[/tex].

somasimple

Once again you reply...at left of the question.
I'm asking if the function is discontinous in t and your example has little to see with a real cable carrying a real electrical signal.

And what is the value of x in your example?

DaleSpam

The more I think about this question the more I realize you are right. My posts to you are obviously futile. You are clearly not interested in anything I say, only in pushing your weird anti-HH agenda. Your posts to me are equally futile. I generally cannot even understand your ideas due at least in part to the language barrier. The only remotely useful thing of any of your posts are the interesting references, but I can get those from Google with much less hassle.

Anyway, goodbye somasimple. I expect that you will find other people willing to continue the conversation.

somasimple

No, DaleSpam
You're only taking me for an idiot.
http://www.myreckonings.com/wordpres...eEquations.jpg
Please are you able to record such a signal in a cable or an axon? Just no!
Every time you are faulty you bring an obscure statement or function that has no relation with the discussion.
As I said it earlier you are not obliged to try to reply systematically in opposition: That is not a scientific behavior...
Goodbye you had already proved your... talent.

granpa

I'm afraid dale is right. this has become tiresome. you shoot down anything I say while making vague cryptic references to some theory of yours that you never bother to explain. I dont even know what it is that you are arguing and this is page 9. really enough is enough.

atyy

Points in this post are my interpretation of: Ritchie, Physiology of Axons in "The Axon: Structure, Function and Pathophysiology" ed. Waxman, Kocsis and Stys, OUP 1995.

1. Myelinated axons conduct faster (v~d) than unmyelinated axons (v~sqrt(d)), where v is the speed across nodes and internodes. The key for this is the length constant, as I suspected from dimensional considerations in earlier posts. (Lussier and Rushton 1951).

2. There are references for the computation of velocity in axons, but I do not know whether this is across nodes and internodes, or whether they can also compute a separate internode velocity. (Blight 1985, Brill et al 1978, Dodge 1963, Fitzhugh 1962, Goldman and Albus 1968, Hardy 1973, Hutchinson et al 1970, Koles and Rasinsky 1972, Moore et al 1978, Ritchie and Stagg 1982, Schauf and Davis 1974, Waxman and Brill 1978, Wood and Waxman 1982)

3. There is criticism of the "classical" passive internode model and the neglect of a conduction pathway beneath the myelin, especially for mammalian myelinated axons. (Barrett and Barrett 1982, Blight 1985, Blight and Someya 1985, Bowe et al 1987). Quote for somasimple: "The internodal membrane not only has a capacitance two to three orders of magnitude greater than that of the node, but also contains a repertoire of ionic conductances...".

4. There is criticism of Rushton's analysis for small myelineated axons: "Rushton's belief that conduction velocity of PNS myelinated nerve fibers falls off markedly ... may be correct, but perhaps for a different reason from the one he proposed..."

5. "The studies of Moore et al (1978) show that internodal parameters control the conduction velocity far more than does the node itself. They help account for the insensitivity to the nodal constriction that is characteristic of myelinated fibers."

6. "[referring to activation rate constants] Why this should be so is unclear. Indeed it should be pointed out that the conduction velocity of a mammalian nerve fiber at 37^oC can be simulated reasonably well only if these activation constants are brought into line with the squid giant axon value of 3 (Ritchie and Stagg 1982)."

atyy

Hi somasimple, I'm done with the discussion too - but I think your points are excellent. This is really getting into specialist territory, and I'm not personally inclined to pursue the details further. Much luck on your studies!

somasimple

The content of this thread was started to elucidate if 2 or more nodes are active during a single message propagation. This is a complex subject and solitons are much more complex.
You question about inductance, water... are far out the subject.

Atyy,
Thanks for the support.
I'll take a closer look at references.
ps: the Koch's book is disappointing: it contains quite nothing on the subject.
BTW, it gives more numbers and some graphs show strange results...

granpa

http://en.wikipedia.org/wiki/Polaron

http://en.wikipedia.org/wiki/Piezoelectric

somasimple

Interesting concepts but what is the relation with the current subject?

granpa

no particular relation. just showing that ions and electric fields can and do interact with phonons. hence the possibility of an electrical signal propagating at the speed of sound.