Walsh Darragh M, Landman Kerry A, Hughes Barry D
School of Mathematics and Statistics, University of Melbourne, Victoria 3010, Australia.
Neurosci Lett. 2017 Sep 29;658:97-101. doi: 10.1016/j.neulet.2017.08.037. Epub 2017 Aug 31.
The myelin sheath that insulates some axons in the central nervous system allows for faster signal conduction. Previously, axons were thought to be either unmyelinated or fully myelinated. Recent experimental work has discovered a new pattern of myelination (intermittent myelination) along axons in the mouse brain, in which long unmyelinated axon segments are followed by myelinated segments of comparable length. We use a computational model to explore how myelin distribution (in particular intermittent myelination) affects conduction velocity. We find that although fully myelinated axons minimize conduction velocity, varying the spatial distribution of a fixed amount of myelin along a partially myelinated axon leads to considerable variation in the conduction velocity for action potentials. Whether sodium ion channel number or sodium ion channel density is held constant as the area of the unmyelinated segments increases has a strong influence on the optimal pattern of myelin and the conduction velocity.
在中枢神经系统中，包裹某些轴突的髓鞘可实现更快的信号传导。此前，轴突被认为要么无髓鞘，要么完全被髓鞘包裹。最近的实验研究发现，小鼠大脑中的轴突存在一种新的髓鞘形成模式（间歇性髓鞘形成），即长的无髓鞘轴突段之后是长度相当的有髓鞘段。我们使用一个计算模型来探究髓鞘分布（特别是间歇性髓鞘形成）如何影响传导速度。我们发现，尽管完全髓鞘化的轴突能使传导速度最小化，但沿着部分髓鞘化的轴突改变固定量髓鞘的空间分布会导致动作电位的传导速度出现相当大的变化。随着无髓鞘段面积的增加，钠离子通道数量或钠离子通道密度保持不变，这对髓鞘的最佳模式和传导速度有很大影响。
