Abstract: This report examines the Extracellular-Membrane-Intracellular (EMI) framework for modeling action potentials along 3D axons. We investigate the effect of myelination and the potential for ephaptic coupling in this model. Additionally, we assess the convergence and stability of a range of Runge-Kutta time-stepping algorithms on simple geometries with manufactured solutions.We first analyze single axons and the influence of myelin on the speed of action potentials. Then, we use a 3D geometry of nine cylinders to represent an axonal bundle and study the induced potential in the central axon in both myelinated and unmyelinated cases. Finally, we discuss the biological implications of ephaptic coupling and the importance of 3D modeling for precise simulations of spiking neurons.