Nerve system

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ffixcth
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Nerve system

Post by ffixcth » Wed Feb 16, 2005 1:47 pm

Along the nerve fibre, there is layer of fatty substance (myelin sheath) that surround the nerve to protect it. At intervals, the myelin sheath will sinks down and in contact with the nerve fibre, the area is called the nodes of Ranvier. According to the notes, the nodes of Ranvier can speed up the transmission of impulse along the nerve fibres. Can anyone explain to me how the node of Ranvier work to speed up the tramission of impulse?

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Poison
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Post by Poison » Wed Feb 16, 2005 4:35 pm

When myelin sheat is present the impuls travels by jumping. (i think that word is proper to explain). This way of travelling speeds up the transmission of impulse.
Otherwise the impulse travels like walking.

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Post by ERS » Wed Feb 16, 2005 6:13 pm

The "jumping" you are refering to is called saltatory conduction. The nodes of Ranvier are important because the impulse doesn't need to depolarize each area of the membrane, just at the nodes. So in effect the impulse can just cruise on down a myelinated fiber without the "speed bumps" of depolarization.

that help any?
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Poison
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Post by Poison » Wed Feb 16, 2005 6:17 pm

My answer was a bit like a story,i guess. I tried to make it simpler. :lol:

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Post by ERS » Wed Feb 16, 2005 6:24 pm

Hey I got what you were saying Poison! Just trying to add here and there;-)
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Poison
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Post by Poison » Wed Feb 16, 2005 6:26 pm

I c. I must admit that your answer was more scientific. :D

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Post by MrMistery » Mon Mar 07, 2005 8:51 pm

The myelin sheth acts like an isolator for electrical power(the electric impulse is electrical in nature), the only parts of the membrane that can be depolarised are the nodes of Ranvier(this was explained very well by ERS). This makes the electrical impulse go much faster(120m/s) than in an axon without myelin sheth(1-2m/s). The humans, among other animals, posses neurons which have axons with a myelin sheth.
The nervous impulse at the octopus travels rather fast(50m/s), but this is done without myelin sheth, by incrreasing the dyameter of the axon(they are called giant nervous fibres)
PS: mine was even more scientific :D
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Post by Poison » Tue Mar 08, 2005 4:19 pm

Yes it is. :lol:
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