Sharmin Sabrina, Karal Mohammad Abu Sayem, Mahbub Zaid Bin, Rabbani Khondkar Siddique-E
Department of Physics, Bangladesh University of Engineering and Technology, Dhaka, Bangladesh.
Department of Arts and Sciences, Ahsanullah University of Science and Technology, Dhaka, Bangladesh.
Front Neurosci. 2023 Apr 17;17:1084004. doi: 10.3389/fnins.2023.1084004. eCollection 2023.
Based on published experimental evidence, a recent publication revealed an anomalous phenomenon in nerve conduction: for myelinated nerves the nerve conduction velocity (NCV) increases with stretch, which should have been the opposite according to existing concepts and theories since the diameter decreases on stretching. To resolve the anomaly, a new conduction mechanism for myelinated nerves was proposed based on physiological changes in the nodal region, introducing a new electrical resistance at the node. The earlier experimental measurements of NCV were performed on the ulnar nerve at different angles of flexion, focusing at the elbow region, but left some uncertainty for not reporting the lengths of nerve segments involved so that the magnitudes of stretch could not be estimated.
The aim of the present study was to relate NCV of myelinated nerves with different magnitudes of stretch through careful measurements.
Essentially, we duplicated the earlier published NCV measurements on ulnar nerves at different angles of flexion but recording appropriate distances between nerve stimulation points on the skin carefully and assuming that the lengths of the underlying nerve segment undergoes the same percentages of changes as that on the skin outside.
We found that the percentage of nerve stretch across the elbow is directly proportional to the angle of flexion and that the percentage increase in NCV is directly proportional to the percentage increase in nerve stretch. Page's L Trend test also supported the above trends of changes through obtained values.
Our experimental findings on myelinated nerves agree with those of some recent publications which measured changes in CV of single fibres, both myelinated and unmyelinated, on stretch. Analyzing all the observed results, we may infer that the new conduction mechanism based on the nodal resistance and proposed by the recent publication mentioned above is the most plausible one to explain the increase in CV with nerve stretch. Furthermore, interpreting the experimental results in the light of the new mechanism, we may suggest that the ulnar nerve at the forearm is always under a mild stretch, with slightly increased NCV of the myelinated nerves.
基于已发表的实验证据，最近的一篇论文揭示了神经传导中的一个异常现象：对于有髓神经，神经传导速度（NCV）随拉伸而增加，然而根据现有的概念和理论，由于拉伸时神经直径减小，情况本应相反。为了解决这一异常现象，基于结区的生理变化提出了一种新的有髓神经传导机制，即在节点处引入了新的电阻。早期对NCV的实验测量是在不同屈曲角度的尺神经上进行的，重点在肘部区域，但由于未报告所涉及神经节段的长度，使得无法估计拉伸幅度，从而留下了一些不确定性。
本研究的目的是通过仔细测量将有髓神经的NCV与不同幅度的拉伸联系起来。
本质上，我们重复了早期发表的关于不同屈曲角度尺神经的NCV测量，但仔细记录了皮肤上神经刺激点之间的适当距离，并假设下方神经节段的长度与皮肤表面的长度经历相同百分比的变化。
我们发现，肘部神经拉伸的百分比与屈曲角度成正比，并且NCV的增加百分比与神经拉伸的增加百分比成正比。佩奇L趋势检验也通过所得值支持了上述变化趋势。
我们对有髓神经的实验结果与最近一些测量有髓和无髓单纤维拉伸时传导速度（CV）变化的出版物一致。综合所有观察结果，我们可以推断，上述最近出版物提出的基于节点电阻的新传导机制是解释CV随神经拉伸增加的最合理机制。此外，根据新机制解释实验结果，我们可以认为前臂的尺神经始终处于轻度拉伸状态，有髓神经的NCV略有增加。
