Final answer:
The Purkinje fibers are specialized myocardial conduction fibers essential to the heart's conduction pathway. They rapidly conduct electrical impulses to the ventricular muscle cells, initiate the contraction at the apex of the heart, ensure coordinated ventricular contraction, and contribute to the overall timing of the cardiac cycle.
Step-by-step explanation:
Description and Functions of Purkinje Fibers
The Purkinje fibers are specialized myocardial conduction fibers that play a critical role in the heart's electrical conduction system.
These fibers originate from the bundle branches and extend throughout the myocardium from the apex of the heart toward the atrioventricular septum and the base. They are responsible for relaying the electrical impulses quickly and efficiently to the myocardial contractile cells of the ventricles.
Four Primary Functions or Characteristics of Purkinje Fibers
Conduction speed: Purkinje fibers have a high inherent conduction rate, allowing the electrical impulse to reach all ventricular muscle cells rapidly - approximately within 75 milliseconds.
Contraction initiation: They ensure that the contraction begins at the apex of the heart and travels toward the base, optimizing the ejection of blood from the ventricles.
Coordination of ventricular contraction: This coordinated contraction pushes the blood out of the ventricles and into the aorta and pulmonary trunk.
Timing of electrical impulse: The time elapsed from the initiation of the impulse in the sinoatrial (SA) node until the depolarization of the ventricles by the Purkinje fibers is about 225 milliseconds.
The total coordination in the cardiac conduction system - involving the SA node, AV node, bundle branches, and Purkinje fibers - contributes to the effective pumping of blood throughout the body, as represented by a complete cardiac cycle on an electrocardiogram (ECG).