tigress

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Could anybody explain the whole concept of myelination to me? I don't really understand why it speeds up the transmission of action potential along the axon. Does anybody know of a good resource to look in for an explanation?

Oh, and so far I think the TPR review books have been great, but I find the bio review lacking when it comes to neurology. Anybody else? It might just be because I don't have a great background in the area to begin with...
 

proteolytic

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tigress said:
Could anybody explain the whole concept of myelination to me? I don't really understand why it speeds up the transmission of action potential along the axon. Does anybody know of a good resource to look in for an explanation?

Oh, and so far I think the TPR review books have been great, but I find the bio review lacking when it comes to neurology. Anybody else? It might just be because I don't have a great background in the area to begin with...
In a more physical sense the myelination increases the membrane resistance thereby decreasing the capacitance of the membrane. This allows the potential difference to be propagated further without a loss of current through leak channels. Thus allowing the potential to travel further with faster conduction speed.

Words ought to be a little wild for they are the assaults on thoughts of the unthinking
John Maynard Keynes
 

Lindyhopper

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Compare the unmyelinated nerve to a soaker hose. Mylelination is like insulation. If one insulated the soaker hose, water would no longer leak out and, therefore, would more quickly & forcefully rush along the length of the hose. Similiarly, as the myelinated nerve would no longer "leak" ions, the charge will more quickly move travel along the length of the axon until it came to the next leaky node.
 
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tigress

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thanks, I understand it better now. What I wasn't getting was that it was due to ions not leaking out where the myelin is. I couldn't understand why the action potential would jump from node to node faster, but I guess it's because the Na+ comes in and K+ isn't leaking out as much? But in that case, wouldn't it make the refractory period longer, because there isn't as much space for voltage-gated K+ channels to repolarize the membrane?