Myelin Conduction: Explaining Depolarization & Current Sinks

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sameeralord
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Hello everyone,

I don't understand how depolarisation jumps when axons are myelinated. Ok myelin is an insulator so in that section no current passes through. But how does that make the current jump, when current reached myelin wouldn't it be inhibited, why does it still travel. Also what do they mean by developing current sinks at nodes of ranvier. Thanks :smile:
 

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sameeralord said:
Hello everyone,

I don't understand how depolarisation jumps when axons are myelinated. Ok myelin is an insulator so in that section no current passes through. But how does that make the current jump, when current reached myelin wouldn't it be inhibited, why does it still travel. Also what do they mean by developing current sinks at nodes of ranvier. Thanks :smile:

the current does not pass through the myelin. The myelin is wrapped around the neuron (like a plastic insulator is wrapped around copper wires). This prevents charge leakage, since (as you say) current can't pass through an insulator.

The mechanism is called "saltatory conduction" for your research pleasure.
 
Myelin acts as an insulator between nodes creating a defacto capacitor like linkage, the impedance of capacitors is high to DC and low to AC while nerve condution is low frequency compared to most communications it is still high enough to transmit like AC.

Think of the myelin sheath and nodes as being a series of capacitors not only faster but more efficient as only the membrane in the node needs to repolarize after each transmission