At the end of diastole, the contraction of the auricles (or auricular systole) completes the filling of the ventricles. The closing of the mitral and tricuspid valves then produces a muffled sound.
At the end of diastole, the contraction of the auricles (or auricular systole) completes the filling of the ventricles. The closing of the mitral and tricuspid valves then produces a muffled sound.