According to this:

A nerve fibre cannot be fatigued, even if it is stimulated for a long time. This property of infatiguability is due to absolute refractory period.

How is refractory period related to infatiguability?

My attempt: If there were no absolute refractory period, then there will not be closure of Na+ ions into cell, so there will be temporary deficiency of Na+ at that location, now if a new action potential arrives at that point then , due to lack of Na+ there will not be further conduction of it.

Is my conjecture correct?

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    $\begingroup$ What exactly is your question? Is it why nerves don't get tired, or whether your conjecture is correct? $\endgroup$ – another 'Homo sapien' Jul 20 '17 at 12:51
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    $\begingroup$ Is my conjecture correct? $\endgroup$ – JM97 Jul 20 '17 at 12:58
  • $\begingroup$ Then it seems my awnser isn't what your looking for, but the conjecture is not quite right. It isnt a lack of ions, but rather the sodium gates are inactivated (and cannot open) that causes a absolute refractory period. $\endgroup$ – xelo747 Jul 20 '17 at 13:04
  • $\begingroup$ I really don't understand the reason for down vote. $\endgroup$ – JM97 Jul 20 '17 at 13:19
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    $\begingroup$ If you study the electrical function of the nerve, it does exhibit attenuation to repeated signals, and there are various electrical stabilization times for the stasis within and outside the nerve to reach a balance after stimulation. ou should read about nerve disorders and nerve fatigure research to get an idea of how they malfunction. this is not recent but it could be interesting: onlinelibrary.wiley.com/doi/10.1113/jphysiol.1906.sp001147/pdf $\endgroup$ – com.prehensible Jul 20 '17 at 19:47

One can imagine that each action potential causes a small amount of $\ce{Na+}$ goes inside the cell, and a small amount $\ce{K+}$ goes outside the cell, thus weakening the electrochemical gradient of both ions. If each action potential has (approximately) the same flux of $\ce{Na+}$ and $\ce{K+}$ then higher frequency of action potentials means more flux, thus a quicker depletion of the electrochemical gradients. The absolute refractory means there is a maximum firing frequency.

Thus the Sodium-Potassium pump only needs to be able to "recharge" the maximal possible depletion of ion's gradients. If there was no absolute refractory period then theoretically the action potential frequency could be faster than the Sodium-Potassium pump can keep up. A abnormally fast firing rate in theory could deplete the potassium gradient and sodium gradient thus would result in a fatigued neuron.

Edited to add in reference to the conjecture: Absolute refractory periods are cause by sodium gate inactivation, thus no matter how much current one adds the sodium gates will not open until sodium inactivation ends. However, over long periods of time (in seconds) and in the absences of a ionic pump, the lack of sodium (and potassium) gradients will cause fatigue.

However, "fatigued" neurons may not act like one expects.

  • $\begingroup$ Hopefully, the edit clarifies. $\endgroup$ – xelo747 Jul 20 '17 at 13:13
  • $\begingroup$ You mean lack of gradient? because Brayn Krauss comment on this question says so biology.stackexchange.com/questions/62826/… $\endgroup$ – JM97 Jul 20 '17 at 13:20
  • $\begingroup$ Yes I do mean lack of gradeint. I will edit for clarity when I return to my desktop. $\endgroup$ – xelo747 Jul 20 '17 at 13:36
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    $\begingroup$ @LéoLéopoldHertz준영 thats a complicated question, and the linked paper gives some possible side-effects such as hyper-excitablility. It's counter-intuivite so I left it out, and gave a link for the more interested reader. Perhaps a separate question would be good? $\endgroup$ – xelo747 Jul 20 '17 at 16:16
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    $\begingroup$ @xelo747 No, I do not think so. It is part of the topic here. Please, add a section about it in your answer stating some of the factors. $\endgroup$ – Léo Léopold Hertz 준영 Jul 20 '17 at 17:12

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