[en] Role of different physical processes, dictating the dynamics of MHD-instability development in Z-pinch constriction, is analyzed. The role of magnetic field diffusion and plasma radiation in approximation of Bremsstrahlung losses is investigated. Numerical simulation is conducted with the use of two-dimensional MHD program MAG. The main attention is paid to dynamics of shock wave movement, its coming out to the system axis and hot point formation. The successive evolution of the hot point shows, that shock waves begin to propagate from it in axial direction along Z axis. 6 refs., 3 figs