Purkinje system: role in inducing synchronized contraction of the ventricular muscle

2021-06-01 12:58 PM

When the impulse reaches the ends of the Purkinje fibres, it is transmitted through the ventricular muscle mass by the ventricular muscle fibres themselves. The conduction velocity is now only 0.3 - 0.5m/s, which is 1/6 of the Purkinje fibres.

The rapid conduction of the normal Purkinje system allows cardiac impulses to reach virtually all parts of the ventricles in a narrow interval of time, stimulating the first ventricular muscle fibres only 0.03-0, 06 seconds before stimulation of the last ventricular muscle fibres.

This time causes all parts of the ventricular muscle in both ventricles to start contracting at roughly the same time and then continue to contract for about 0.3 seconds more.

Efficient pumping by the two ventricles requires this type of contractility. If the cardiac impulse passes through the ventricles slowly, most of the ventricular muscle mass will contract before the rest, in which case the overall pumping efficiency will be greatly reduced. Indeed, in some types of heart failure, conduction retardation occurs, and the pumping efficiency of the ventricles is reduced by almost 20 to 30%.