action potential - neuroscientific Achilles heel

chris hickie chickie at girch1.med.uth.tmc.edu
Mon May 9 19:57:55 EST 1994


In article <JcwsU7y.gokelly at delphi.com>, GREGORY C.O'KELLY
<gokelly at delphi.com> wrote:
> 
> It is important to keep in mind, while reading the paper "Action Potentials - Honored Tradition or Alarming Embarrassment", that the equation W = f x d is Dr. Koester's equation, and he is not clear as to what f is.  One might think that it is electrosta
> tic or electromotive force, but this, as potential difference, is a voltage, and not really a force at all.  So Dr. Koester's diagrams on p. 1035 relating force to distance have no application at all in this case because distance, d, is already contained
>  in potential difference.  The area under the curve, or work, is more truly W = C x Vsquared/2, which is the integral (and therefore the area under the curve) for Q = CV.  This oversight on Dr. Koester's part is why he concludes, incorrectly, that increa
> sing d decreases capacitance.  If d increases, then V must diminish, so that if Q is to remain the same, capacitance must increase.  The only way for V to remain the same if d increases, is for Q to increase.
> 	I find it exasperating to here again and again from neuroscientific types whose living depends upon the perpetuation of such errors, that I don't understand electricity because I use the equation W = f x d as if I were giving my approval to its use when
>  that equation is Dr. Koester's, and not pertinent at all to electrical circuitry.  I try to point out the weaknesses of that equation, and how Dr. Koester's definition of f (in fact he doesn't really give one, just hints at it) is mistaken.  Impugning m
> y understanding of electricity tells me that the critic is projecting his own ignorance, and that the critic probably makes a good salary and has status as a neuroscientist in the perpetuation of what can only really be described as despicable and shoddy
>  science and self-serving sciolism.

Where do I begin?  Hmmm....

1) I find it exasperating when people don't hit carriage returns more
often. (does carriage return at 80
      characters mean anything to you?)

2) You are correct in that W = C*(V^2)/2, but this is for the work done
charging the capacitor, not the
     work done in moving an infinitesimal charge from one side of the
capacitor to the other once it has been
      charged.   I believe Dr. Koester is talking about the latter case.  

3) The integral of a force over a distance is an extremely pertinent
quantity called work.  If you know
      the force function and you know the path over which an object is
moved, you can calculate
      the work required to move that object, be it a person or an electron.
 I will grant you
      that for absolute generality,  W should be defined as an integral,
which it is on page 1033 of
      Appendix A. The remainder of the discussion seems geared towards
students with little
      or no calculus background, hence the lack of integration and also the
lack of derivatives needed
      to explain quantitatively the charging of a capacitor as a function
of time once a switch is closed.
      (In a way, it's a shame introductory books can't assume a higher
level of math literacy in
      students today) Go read Halliday and Resnick's Physics, chapters
27-32 of the third edition, 
       (1978) for derivations that I'm sure will be more to your liking. 

4)  Nobody's impugning you.  I just wish you'd stop making these vague
and/or incorrect references 
       to prior neuroscience research.  I find it annoying and it projects
your own ignorance.

5)  Big words don't fool everyone.  If you can't state it in a simple
manner, it probably isn't worth
       stating.

6)  I make jack sh*t for a salary as a grad student; my career hopes, like
many young scientists are
       bleak,  too.  What exactly is your background, anyhow?  You sure act
like you live in your
       own ivory tower.  
      
7)  If this one *trivial* complaint is the basis of your whole "revolution"
in neuroscience,
       then maybe you better find a new central tenet around which to base
your arguments.


Chris 



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