Conducting System of the Heart

CONDUCTING SYSTEM OF THE HEART

The conducting system of the heart is a specialized system of cardiac muscle fibers that generates and transmits electrical impulses. These impulses control the rhythmic contraction of the heart.

Components of the Conducting System:

Sinoatrial Node (SA Node)

• Located in the wall of the right atrium near the opening of the superior vena cava
• Known as the pacemaker of the heart
• Generates impulses at a rate of 60–80 beats per minute
• Initiates atrial contraction

SA node cells are electrically unstable and automatically generate impulses, which determine the normal heart rate.

Atrioventricular Node (AV Node)

• Located in the atrial septum near the atrioventricular valves
• Transmits impulses from atria to ventricles
• Introduces a delay of about 0.1 second, allowing atria to complete contraction before ventricles begin
• Can act as a secondary pacemaker with a rate of 40–60 bpm

AV Bundle, Bundle Branches and Purkinje Fibers

• The bundle of His arises from the AV node
• It divides into right and left bundle branches in the ventricular septum
• These branches break into fine fibers called Purkinje fibers

These fibers spread impulses rapidly throughout the ventricular myocardium, causing coordinated ventricular contraction from the apex upward.

Nerve Supply to the Heart

The heart is regulated by the autonomic nervous system.