Difference Between SA And AV Nodes

The heart is a pump made up of muscle tissue. Like all muscle, the heart needs a source of energy and oxygen to function. The heart’s pumping action is regulated by an electrical conduction system that coordinates the contraction of the various chambers of the heart. The Electrical pulses in the heart are controlled by special groups of cells called nodes.

What Is Sino-atrial (SA) Node?

The sinoatrial node (SA node) is a specialized myocardial structure that initiates the electrical impulses to stimulate contraction and is found in the atrial wall at the junction of superior caval vein and the right atrium (the right upper chamber of the heart).

The SA (sinoatrial) node generates an electrical signal that causes the upper heart chambers (atria) to contract. The signal then passes through the AV (atrioventricular) node to the lower heart chambers (ventricles), causing them to contract or pump. AV node serves as a gate that slows the electrical current down through to the ventricles. This delay ensures that the atria have a chance to fully contract before the ventricles are stimulated.

The SA node is considered the pacemaker of the heart. Its electrical signals normally cause the atria of an adult’s heart to contract at a rate of about 60 to 100 times a minute.

What You Need To Know About SA Nodes

• SA Node is a small mass of tissue in the right atrium functioning as pacemaker of the heart by giving rise to the electric impulses that initiates heart contractions.
• SA nodes are longer, flattened and ellipsoidal.
• It is present in the right atrium near the opening of the superior vena cava.
• SA node is larger in size as compared to AV node.
• SA generates cardiac impulses.
• The firing rate of the SA node is 60-100 bpm.
• SA node transmits cardiac impulses directly to the right and left atrium.
• SA node serves as the pacemaker of the heart.
• The Autonomic nervous system regulates SA node.
• SA node has the maximum rhythmicity.

What Is Atrio-ventricular (AV) Node?

The atrioventricular node or AV is a part of electrical conduction system of the heart that coordinates the top of the heart. It electrically connects the atria and ventricles. The AV node lies at the lower back section of the interatrial septum near the opening of the coronary sinus and conducts the normal electrical impulse from the atria to the ventricles.

In other words, AV node serves as an electrical relay station, slowing the electrical current sent by the sinoatrial (SA) node before the signal is permitted to pass down through to the ventricles. This delay ensures that the atria have an opportunity to fully contract before the ventricles are stimulated. After passing the AV node, the electrical current travels to the ventricles, along special fibers embedded in the walls of the lower part of the heart. The AV node, which controls the heart rate, is one of the major elements in the cardiac conduction system.

What You Need To Know About AV Nodes

• AV Node is a small mass of tissue that is situated in the wall of the right atrium and passes impulses received from the SA node to the ventricles.
• The AV nodes are short and half-oval.
• It is present in the right atrium at the base of the inter atrial septum or we can say near the opening of the coronary sinus.
• AV node is smaller in size as compared to SA node.
• AV node relays the cardiac impulses generated by SA node and intensifies them.
• The intrinsic firing rate of the AV node is 40-60 bpm.
• AV node carries the impulse to the two ventricles through AV bundle, its branches and terminal strands.
• AV node serves as the pacesetter of the heart.
• AV node is regulated by the SA node.
• It has less rhythmicity than SA node.

Difference Between SA And AV Nodes In Tabular Form