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首页> 外文期刊>Journal of Computational Neuroscience >The 'Lillie Transition': models of the onset of saltatory conduction in myelinating axons
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The 'Lillie Transition': models of the onset of saltatory conduction in myelinating axons

机译：“莉莉过渡”：髓鞘轴突中盐分传导的发作模型

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Almost 90 years ago, Lillie reported that rapid saltatory conduction arose in an iron wire model of nerve impulse propagation when he covered the wire with insulating sections of glass tubing equivalent to myelinated internodes. This led to his suggestion of a similar mechanism explaining rapid conduction in myelinated nerve. In both their evolution and their development, myelinating axons must make a similar transition between continuous and saltatory conduction. Achieving a smooth transition is a potential challenge that we examined in computer models simulating a segmented insulating sheath surrounding an axon having Hodgkin-Huxley squid parameters. With a wide gap under the sheath, conduction was continuous. As the gap was reduced, conduction initially slowed, owing to the increased extra-axonal resistance, then increased (the "rise") up to several times that of the unmyelinated fiber, as saltatory conduction set in. The conduction velocity slowdown was little affected by the number of myelin layers or modest changes in the size of the "node," but strongly affected by the size of the "internode" and axon diameter. The steepness of the rise of rapid conduction was greatly affected by the number of myelin layers and axon diameter, variably affected by internode length and little affected by node length. The transition to saltatory conduction occurred at surprisingly wide gaps and the improvement in conduction speed persisted to surprisingly small gaps. The study demonstrates that the specialized paranodal seals between myelin and axon, and indeed even the clustering of sodium channels at the nodes, are not necessary for saltatory conduction.
机译：大约90年前，Lillie报道说，当他用相当于髓鞘节的玻璃管绝缘部分覆盖导线时，神经冲动传播的铁丝模型就出现了快速的盐分传导。这导致他提出了类似的机制来解释髓鞘神经的快速传导。在它们的进化和发展中，有髓轴突必须在连续传导和盐分传导之间进行相似的过渡。实现平滑过渡是我们在计算机模型中研究的潜在挑战，该计算机模型模拟具有Hodgkin-Huxley鱿鱼参数的轴突周围的分段绝缘护套。鞘管下间隙较宽，传导是连续的。随着间隙的减小，由于轴向外轴电阻的增加，传导起初开始变慢，然后随着咸化传导的建立而增加（“上升”）至未髓鞘纤维的数倍。传导速度的降低几乎没有受到影响。髓鞘层的数目或“节”的大小的适度变化，但受“节间”的大小和轴突直径的强烈影响。髓鞘层的数目和轴突直径对快速传导上升的陡度影响很大，受节间长度的影响各不相同，而受结节长度的影响则很小。向盐分传导的过渡发生在出乎意料的大间隙，而传导速度的改善持续到出乎意料的小间隙。研究表明，髓鞘和轴突之间的专门的结旁密封，甚至在结节处钠通道的聚集对于盐分传导都是不必要的。

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