Before the ventricular apex is excited by the electric front via the Tawara branches and Purkinje fibers, small branches leave the major electrical highways relatively quickly after dividing into a left and a right Tawara branch. These small branches excite the septum and the papillary muscles. This excitation does not extend along the electrical heart axis to the left, but somewhat to the right and then back towards the heart’s base. The leads pointing in the direction of the electric heart axis—and thus away from this septum and papillary nerve excitation—will initially show a small negative deflection. Here, we refer to the physiological "septal Q". After reaching the apex, as indicated by the R wave, the heart base is depolarized. Again, there is a negative deflection, called the S wave, in leads running along the electric heart axis.