The8

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Does axon length affect the speed of the neuron. Altius says no, but I say they are wrong, in fact axon length by increasing resistance lowers current and thereby lowers speed.
 

laczlacylaci

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Jun 20, 2016
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No, I don't think the length has anything to do with it. If you think about it, as you increase the length of the axon, you increase the # of nodes of ranvier, which increases the # of Na+ channels.

the ways to increase increase velocity would be to:
increase axon diameter/radius. This causes less resistance to local currently flow and have faster impulse conduction

effect of myelination vs. no myelination
myelinated axons can conducts signals faster than non-myelinated axons.

You might be referring to length constant?
length constant=sqrt(membrane resistance/internal neuron resistance)
As you length constant increases, the magnitude decreases. (but not the speed)
ie. if you had a 1nm long axon, and let's say 50% of the signal passes to the end.
When you elongate the axons, to let's say 2nm, you might just have 25% of the signal pass to the end.
Lengthening the axon length has nothing to do with speed, but possibly with the voltage magnitude.
 
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The8

The8

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May 22, 2016
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Resistance is proportional to length though.... so from that point I assume current is as well, but I guess the axon is NOT a wire so you are right. I am not sure what you mean by length constant I have never heard that before. But yes, I see so you are saying that the additional nodes keep speed constant.... still what if you were to change DENSITY by actually making there less per wire length.... would this cause a decrease in speed then!?

@laczlacylaci