Body Fluids And Circulation

SA node is called the ‘heart of heart’. The contraction in the heart is initiated by a structure made up of modified heart muscles called Sino-Atrial Node (SA Node). The SA node is located in right atrial wall below the opening of the superior vena cava. It initiates the contraction in the heart which is then spread to the entire heart through the network of fibres. Since it is responsible for initiating contraction, it is also called as ‘pace maker’ or ‘heart of heart’. 

The other node AV node is called the pace setter. AV node passes the contraction generated by the SA node to the bundle of his which is further passed through the fibrous network to the remaining parts of the heart. Purkinje fibres carry the impulse through bundle of his to the ventricular muscles.