A) Atrio-ventricular node-bundle of His-Sino-atrio node-network of Purkinje fibres
B) Network of Purkinje fibres-Atrio-ventricular node-Sino-Atrio node-bundle of His
C) Atrio-ventricular node-Sino-Atrio node-bundle of His-Purkinje fibres
D) Sino-atrial node-Atrio-ventricular node- bundle of His-Purkinje fibres
E) Sino-atrial node-Atrio-ventricular node- Purkinje fibres-bundle of His
Correct Answer: D
Solution :
The origin of heart beat and .their conduction is represented in the pathway as follows- Sino-atrial node or SA node initiates origin of cardiac impulses. Its muscle fibres possess highest rhythmicity among all cardiac muscle fibres and initiate excitory waves at the highest rate. SA node is located in right atrium. It is also called the pacemaker. Atrio-ventricular node or AV node is situated at the posterior right border of the interauricular septum. The impulses reach AV node after spreading over the atria and suns along the AV bundle. Bundle of His was discovered by His in 1893 in heart of mammals. These are actually the AV bundles, which get branched into muscle fibres to spread the impulse. Purkinje fibres are specialized cardiac muscle fibres, branched through bundle of His to spread the cardiac impulse to reach the ventricular muscle fibres.
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