The correct sequence of parts that carry cardiac impulses is:
A.
AV node, SA node, Purkinje fibers, AV bundle.
B.
SA node, Purkinje fibers, AV node, AV bundle.
C.
SA node, AV node, AV bundle, Purkinje fibers.
D.
AV node, AV bundle, Purkinje fibers, SA node.
The Correct answer and Explanation is:
The correct sequence of parts that carry cardiac impulses is:
C. SA node, AV node, AV bundle, Purkinje fibers.
Explanation:
The cardiac impulse conduction system ensures that the heart beats in a coordinated manner, allowing for efficient blood flow through the chambers. Here’s a detailed breakdown of the sequence:
- SA Node (Sinoatrial Node): The process begins at the SA node, located in the right atrium near the opening of the superior vena cava. The SA node is known as the heart’s natural pacemaker. It generates electrical impulses at regular intervals, which initiate each heartbeat. The impulse travels through the atrial walls, causing the atria to contract and push blood into the ventricles.
- AV Node (Atrioventricular Node): After passing through the atria, the electrical impulse reaches the AV node, situated at the junction between the atria and ventricles. The AV node serves as a critical gateway that briefly delays the impulse. This delay is essential because it allows time for the ventricles to fill with blood from the atria before the ventricles contract. The delay also ensures that the ventricles receive a coordinated signal for efficient pumping.
- AV Bundle (Bundle of His): The impulse then travels from the AV node to the AV bundle, also known as the Bundle of His. This bundle is located in the interventricular septum and splits into two branches: the right bundle branch and the left bundle branch. The AV bundle conducts the impulse from the AV node to the Purkinje fibers.
- Purkinje Fibers: Finally, the impulse reaches the Purkinje fibers, which are specialized conducting fibers distributed throughout the ventricles. The Purkinje fibers rapidly transmit the electrical impulse throughout the ventricular walls, ensuring a synchronized contraction of the ventricles. This coordinated contraction effectively pumps blood out of the heart to the lungs and the rest of the body.
This precise sequence allows the heart to maintain a rhythmic and effective pumping action, crucial for sustaining proper circulation and overall cardiovascular function.