IUBio

Action Potential

Jeff Wilson wilsonj at smtplink.ipfw.indiana.edu
Mon Dec 16 11:00:34 EST 1996


Ralph Leonhardt <leo at neuroinformatik.ruhr-uni-bochum.de> wrote:


>On Thu, 12 Dec 1996, Jeff Wilson wrote:

>> 
>> Briefly, then, between nodes the potential travels at a speed
>> approaching the speed of light ...
>> 

>Frankly, this is nonsense. Although, on the whole Jeff's explanation of 
>action potential conduction is pretty convincing.

>All the best, Leo

"Nonsense?"  Them's fightin' words!  :)   However, I appreciate the
kind words about the rest of my explanation.

Granted my statement is perhaps an oversimplification, ignoring the
effects of capacitance on the potential between the nodes (yes, I know
-- this is like ignoring gravity in considering the path of a
projectile).  My point is that the potential at the next node _begins_
to change virtually instantly, because the space constant is
lengthened so much in the myelinated axon.  Of course the peak of the
potential will not occur simultaneously with the peak of the action
potential at the previous node, nor will the peak of the potential be
as high, but it will be large enough to reach threshold and trigger an
action potential.

No, I'm not a physiologist, but I play one in the classroom. :) 
(scary thought, isn't it!)

Jeff Wilson
wilsonj at smtplink.ipfw.indiana.edu




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