Biosimulation models of the heart action potential have become a very useful tool. It provides better understanding for the complex biophysical phenomena related to electrical activity in the heart such as cardiac arrhythmias. At cellular level, the electrical activity of cardiac tissues may be simulated by solving a system of ordinary differential equations (ODEs) describing the electrical behavior of the cell membrane. Because the biophysical processes underlying this phenomenon are non-linear and change very rapidly, the ODE system is a challenge to be solved numerically. Furthermore, the implementation of these models is a hard task for commercial finite element software. In this paper a finite element formulation, model and code generation of monodomain equation has been conducted. The developed code is coupled with the modified FitzHugh-Nagumo (FHN) cell electrophysiological model in order to have isotropic excitation propagation starting from cell level to complete heart level. MATLAB programming language was used to build the proposed standalone finite element code. A two dimensional specimen of heart tissues is simulated to show the behavior of the excitation propagation and the repolarization phase for isotropic electrical activity. Simulation results of the cardiac action potential have shown good agreements with the experimental measurements obtained from published literature.