神经元轴突电刺激响应的有限元数值模拟

Finite element modeling of current stimulating response on the nerve axon

为了研究神经元轴突的微观生理电传导特性,建立了神经元轴突的三维有限元模型,通过数值计算模拟神经元轴突对电刺激的动态响应。建立海马神经元轴突的三维几何模型并指定其生物物理参数,根据Hodgkin-Huxley方程和Maxwell方程,建立偏微分方程组,对神经元轴突有限元模型施加不同持续时间和不同脉冲幅度的电流脉冲并求解,获得神经元轴突的三维电势分布和动作电位曲线。数值模拟结果显示,该神经元轴突的静息电位约为-65mV;对模型施加持续时间为2ms,强度0.01A/m2的电流脉冲刺激未产生动作电位,施以(2ms、0.2A/m2),(20ms、0.01A/m2),(20ms、0.2A/m2)脉冲刺激均产生动作电位,峰值分别出现在0.012s、0.017s和0.012s,动作电位幅度约为100mV,持续时间约为2ms。神经元轴突电刺激响应的有限元模拟结果与实验结果吻合,表明所建立的神经元轴突有限元模型及数值模拟方法合理、可靠,为深入研究神经电生理特性提供了基础模型和仿真分析方法。

To investigate the characteristics of microphysiological electrical conduction on nerve cell axon, numerical simulation for the dynamic responses of neuronal axon to electrical stimulation is conducted on a three-dimensional （3D） finite element （FE） model. A 3D geometrical model for a segment of a hippocampal neuron axon is developed and assigned biophysical parameters, then the stimulation pulses of various amplitude and duration are imparted on the FE model of neuronal axon. The combination of Hodgkin- Huxley equations and Maxwell equations are performed to get action potential curve and 3D distribution of electric potential. The simulating results show that the resting potential of nerve axon is --65 mV and no action potential occurred under the stimuli of 2 ms duration and 0.01 A/m2 current intensity, whereas the stimuli of （2 ms, 0.2 A/m2）, （20 ms, 0.01 A/m2） and （20 ms, 0.2 A/m2） induced action potentials, and the time arrived at the peak value are 0. 012 s, 0. 017 s and 0. 012 s, respectively. The range of actionpotential is 100 mV and duration is 2 ms. The simulation results agree well with that of the experiment, which indicates that both the FE model of neuronal axon and the simulation analysis method are reliable and may contribute to further study on neural electrophysiology.