College of Massage Therapists of British Columbia (CMTBC) Practice Exam

What is the primary function of Purkinje fibers?

1. Transmission of nerves

2. Contraction of cardiac muscle

3. Conduction of electrical impulses

4. Regulation of heart rate

The correct answer is: Conduction of electrical impulses

The primary function of Purkinje fibers is the conduction of electrical impulses within the heart. These specialized fibers are part of the heart's conduction system, which is crucial for coordinating the heartbeat. When the sinoatrial (SA) node generates an electrical impulse, this impulse travels through the atria, causing them to contract. The impulse then moves to the atrioventricular (AV) node and, from there, travels down the bundle of His and into the Purkinje fibers. Once the impulses reach the Purkinje fibers, they rapidly distribute the signal throughout the ventricles, leading to coordinated contraction of the ventricular muscle. This ensures that blood is efficiently pumped from the heart to the lungs and the rest of the body. While the Purkinje fibers play a role in contracting cardiac muscle by facilitating the spread of electrical signals, their primary role is in conducting these impulses rather than being the source of the actual muscle contraction itself. Regulation of the heart rate is primarily managed through other mechanisms, including autonomic nervous input and hormonal influences. Hence, the choice concerning the conduction of electrical impulses accurately highlights the main role of Purkinje fibers in cardiac physiology.