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So in nerve impulses, I get that the refractory period is important because it stops the action potentials going the wrong way along the axon. I have two questions:

  1. What would the impact be of the action potential going the wrong way along the axon?
  2. Are there any diseases that maybe cause the refractory period to be shortened so that the action potential goes the wrong way?

Thanks for any help!

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    $\begingroup$ I'll try to write up a full answer unless someone beats me to it... in the meantime, no it isn't really possible for the refractory period to be short enough for the action potential to travel in both directions. You can sort of think about it like the refractory "zone" is "chasing" the action potential down the axon. Making the refractory period shorter in time just shortens in space this refractory "zone". $\endgroup$
    – Bryan Krause ♦
    Commented Feb 8, 2017 at 21:29
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    $\begingroup$ (of course, if you induce an action potential artificially by using an electrical shock midway down the axon, it will travel in both directions; this has some important experimental implications but wouldn't occur otherwise in most neurons of a vertebrate nervous system) $\endgroup$
    – Bryan Krause ♦
    Commented Feb 8, 2017 at 21:31
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    $\begingroup$ There are some exceptions in insects and some special neurons elsewhere that have a looser definition of axons and dendrites, where signals can propagate in more than one direction, but this is part of the normal function of those circuits. $\endgroup$
    – Bryan Krause ♦
    Commented Feb 8, 2017 at 21:33

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The propagation of the action potential is MUCH slower than the refractory period. The propagation speed is determined by the cable equation http://www.cnbc.cmu.edu/~bard/passive2/node9.html which is a formalism developed by Hodgkin & Huxley in the 1930s to measure signal transmission through a biological cable (e.g. an axon). The speed of the propagation is measured by a constant. The voltage does decay and thus spread in all directions, but the propagation only matters towards the direction of signal transmission. Ionic action in the soma would destroy the usefulness of transmission not down the axon. With that being said, neurites in arthropod nervous systems for instance http://stg.rutgers.edu/ can receive input and deliver output leading to very complicated patterns of waves inwards and outwards. Despite this, the stomatogastric ganglion can produce very robust and stable rhythmic neural patterns.

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    $\begingroup$ "The propagation of the action potential is MUCH slower than the refractory period" - is this a typo? It is very much not correct. $\endgroup$
    – Bryan Krause ♦
    Commented Feb 14, 2017 at 22:13

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