A 50 year old male patient came with the complaint of palpitations. Examination of pulse revealed irregular heabeat and advised ECG recording. Spread of cardiac impulse is fastest in which of the following structure

Conduction speed in cardiac tissue: Tissue Conduction Rate SA node 0.05 Atrial pathways 1 AV node 0.05 Bundle of His 1 Purkinje system 4 Ventricular muscle 1 Purkinje fibers also have the ability of firing at a rate of 15-40 beats per minute if upstream conduction or pacemaking ability is compromised. In contrast, the SA node in normal state can fire at 60-100 beats per minute. In sho, they generate action potentials, but at a slower rate than sinoatrial node. This capability is normally suppressed. Thus, they serve as the last reso when other pacemakers fail. When a Purkinje fiber does fire, it is called a premature ventricular contraction or PVC, or in other situations can be a ventricular escape. It plays a vital role in the circulatory system. Reference: Ganong's Review of Medical Physiology; 25th edition; Page no: 522