 Dear students, in this topic, we shall discuss the excitatory and conductive system of the heart. The heart has a specialized system for generating rhythmic electrical impulses. It also has a system to conduct these impulses to all parts of the heart rapidly. These impulses cause and control the rhythmic contraction of all chambers of the heart. Dear students, the rhythmicity of these electric impulses generated by the heart cause the contraction of atria about one-sixth of a second ahead of ventricular contraction. This is the rhythm which is found in the middle of all the cardiac chambers, that which chambers will be contracted first and which ones will be contracted later. So, the atria is contracted approximately one-sixth of a second before ventricular contraction. These time-lapse allows the filling of ventricles before they contract. This rhythmity of impulses also allows that when ventricles are contracted, all the muscle fibres, that is, all parts of the ventricles also contract simultaneously. Dear students, the excitatory system of the heart comprises of the pacemaker region, which is also called the sinoatrial or SA node, this pacemaker region in which the rhythmical impulses are generated. Dear students, the components of conductive system of the heart include, number one, the atrial inter-nodal pathways, which conduct impulses from the sinoatrial, that is, SA node, to the AV node. The third component is conductive system's AV node, which conducts impulses into the ventricles. This conductive system's third component, AV bundle, is a bundle of ASB. It conducts impulses from atria into the ventricles. The fourth component of conductive system includes the left and right branches of atrioventricular bundle, or AV bundle. Inko kamalli hum bundle branches bhikatihe. Dear students, the fifth component of the conductive system of heart comprises of the purkinje fibres. These purkinje fibres branch off from the bundle branches. They conduct impulses to all parts of the ventricles.