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Joe Legris jalegris at xympatico.ca
Fri Nov 21 20:43:12 EST 2003

r norman wrote:
> On Fri, 21 Nov 2003 09:44:21 -0500, Joe Legris <jalegris at xympatico.ca>
> wrote:
>>r norman wrote:
>>>The orginal post, snipped away for being non-sensical, did refer to
>>>the nervous system as supplying "electricity" to the body.  However
>>>silly that notion was, it is still true that electricity involves far
>>>more than the movement of electrons -- that is how electric current is
>>>manifested in metallic conductors. Bioelectricity was known since
>>>Galvani's time.
>>>Electrical forces are at work between any two charged bodies. The
>>>energetics of ions moving across a membrane depend on their charge and
>>>the electrical potential, the voltage, as much as they do on
>>>concentrations and diffusion.  The longitudinal flow of ions down
>>>axons is almost entirely a response to electrical forces.
>>>Yes, the real, physical, measurable electric currents that flow during
>>>nerve activity are "electricity". 
>>Longitudinal flow of ions?? There are fast and slow tranport systems for 
>>moving proteins, vesicles, and other chemicals down (and up) the axon, 
>>but if you are talking about action potentials, the net movement of ions 
>>is perpendicular to the axon, not along it. The action potential is the 
>>only thing that "flows" along the axon in that sense, and it is a wave 
>>of depolarization and associated electrical fields, not an ionic 
>>current. If there was a longitudinal flow of ions down the axon there 
>>would have to be a mechanism for supplying them at one end and for 
>>getting rid of them at the other. No such mechanism exists to my knowledge.
> This is very strange.  In another post, you refer to the local current
> loops that are responsible for the propagation of the action
> potential.  These closed loops do involve both transverse or membrane
> currents crossing the membrane and longitudinal currents which travel
> along the axon, up and down its length.  The longitudinal currents are
> caused by spatial variation in potential, dV/dx.  Look at any diagram
> in any text of a local current loop to see what I mean.
> The loops are really quite lengthy.  If an action potential propagates
> at, say, 50 m/sec and lasts for 1 msec, then it is actually some 50 mm
> or 5 cm long. The current loops, themselves, are of comparable size,
> spreading a distance of centimeters down an axon.   Lorente do No
> (1947) mapped the electric field surrounding an axon conducting an
> action potential.  The current lines are easily calculated from the
> isopotential lines and show the extensive longitudinal spread.

I took your phrase "The longitudinal flow of ions down axons" as a net 
DC ionic current along the entire length.

Joe Legris

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