Alteration of neuron structure can induce abnormalities in signal propagation for nervous systems, as seen in traumatic brain injuries, damage and tumours. Here, effects of geometrical changes and damage of neuron structure are investigated in two scaled nerve bundle models, made of myelinated and unmyelinated nerve fibres. We propose a 3D finite element model of a nerve bundle as a unique framework in Abaqus CAE 6.13-3, combining a real-time fully coupled electro-mechanical, modulated threshold for spiking activation and independent alteration of the electrical properties for each 3-layer fibre. The insulation sheath of myelin constricts the membrane deformation and lower strain levels are found at the nerve membrane in the myelinated bundle. The significance of this study is the difference in distribution of residual stresses and strains at the membrane for the different sizes and types of fibres.