current in an axon

egordon at egordon at
Sun Apr 23 18:53:52 EST 1995

This analogy to axonal transmission does not help much in understanding the
biophysics, but does have the virtue of being homely....

I have seen a gas stove that has an elongated burner, with a circumference
of about 60 cm.  When the gas is turned low enough, the flame breaks up
and eventually there is a situation where a two centimetre patch of flame
travels round and round, taking about one second to complete the loop.

There are several points that may be made:
1  There is no longitudinal motion of anything.  There is only the 
   appearance of motion.
2  The buring section can potentially move in either direction, but (once
   started) consistently moves in just one direction.  The same is true in
   axons (prodromic and antidromic conduction).  In both cases the active
   region spreads, but in practice can do so in only one direction, due to
   the other being burnt-out/refractory.
3  Reduce the number of holes in the gas burner, and you will get something
   like saltatory conduction.  (Probably best left as thought experiment!)

Hope this helps.

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