What structure in the heart carries the action potential directly into the contractor fibers of the myocardium?
The correct answer and explanation is:
The structure in the heart that carries the action potential directly into the contractile fibers of the myocardium is the Purkinje fibers.
The Purkinje fibers are specialized muscle fibers that form part of the heart’s conduction system. They branch off from the bundle of His and spread throughout the ventricles, allowing for the rapid transmission of the action potential. These fibers are located beneath the endocardium, the innermost layer of the heart wall. They are larger in diameter compared to other muscle fibers and have a higher conduction velocity, enabling quick propagation of electrical impulses.
The conduction system of the heart is responsible for coordinating the heartbeat. The action potential originates in the sinoatrial (SA) node, the heart’s natural pacemaker, which initiates the electrical signal. From the SA node, the impulse travels through the atria, causing them to contract, and reaches the atrioventricular (AV) node. After a brief delay at the AV node, the impulse moves into the bundle of His, which runs along the interventricular septum. The bundle of His splits into the right and left bundle branches, which eventually lead to the Purkinje fibers.
The Purkinje fibers are crucial for ensuring that the ventricles contract in a coordinated manner. They carry the electrical impulse quickly to the myocardial cells, causing the ventricles to contract from the apex (bottom) upwards towards the base (top), effectively pumping blood out to the lungs and the rest of the body. This efficient conduction helps maintain the heart’s rhythm and ensures the proper functioning of the circulatory system. The Purkinje fibers’ rapid conduction is vital for the synchronization of ventricular contraction and overall cardiac output.