We revisit the Kaluza-Klein theory and solve the field equations of the Kaluza-Klein theory with constant coupling field between the electromagnetic and gravitational field in terms of power expansions in the coordinate for the spherical symmetric case entirely, where is the distance between the gravitational center and the test particle. In the Einstein-Maxwell case where the electromagnetic field and the gravitational fields are coupled linearly, we discuss the exact behavior of the roots of the pseudo potential for the motion of the position as a function of the planar -angle for an orbiting particle. We investigate the analytic continuation of a trajectory of a test particle entering the gravitational center of a central body, which has performed a temporal jump when exiting the gravitational center again. This temporal displacement, if repeated, constitutes a stochastic process that has an expectation value of the reduced Planck constant divided by two times the rest mass of the electron, since the temporal displacement process of the electron goes along with an annihilation and recreation process of the electron that enters and exits the gravitational center. Thus, our finding corresponds to the existence of a Heisenberg uncertainty relation with respect to temporal and energetic fluctuations of the electron in the electron-proton system, which translates to an Heisenberg uncertainty relation with respect to spatial variations and variations in the momentum of the electron in the electron-proton system. The validity of the latter uncertainty relation is equivalent with the existence of a Schroedinger equation governing the statistic behavior of the electron in the electron-proton system. In this way we derive the ground principles of classical quantum mechanics from the unified gravitational theory for gravitation and electromagnetism straightforwardly.