Atrioventricular node

Definition

The atrioventricular (AV) node is a specialized cluster of cardiac muscle cells located between the atria and ventricles of the heart, playing a crucial role in regulating the heart's electrical conduction system. It acts as a gatekeeper, receiving electrical signals from the sinoatrial (SA) node and delaying them before they pass into the ventricles, ensuring coordinated contraction of the heart. This function is essential for maintaining proper systemic and pulmonary circulation, as it allows the atria to fully contract and empty their blood into the ventricles before they begin to contract.

5 Must Know Facts For Your Next Test

1. The AV node has a slower conduction velocity compared to other parts of the conduction system, allowing time for the atria to contract fully before the ventricles contract.
2. The AV node can act as a secondary pacemaker if the SA node fails, firing at a slower rate than the SA node to maintain some heart rhythm.
3. In cases of complete heart block, signals from the atria can be completely blocked from reaching the ventricles through the AV node, leading to a dissociation between atrial and ventricular activity.
4. The delay created by the AV node is critical for effective filling of the ventricles, which optimizes blood flow through both systemic and pulmonary circuits.
5. The autonomic nervous system influences the activity of the AV node; sympathetic stimulation increases heart rate while parasympathetic stimulation decreases it.

Review Questions

• How does the atrioventricular node contribute to the coordination of heart contractions?
  • The atrioventricular node plays a key role in coordinating heart contractions by receiving electrical impulses from the sinoatrial node and delaying them before sending them to the ventricles. This delay ensures that the atria have enough time to fully contract and empty their blood into the ventricles before those chambers contract. This timing is crucial for maintaining efficient blood flow throughout both systemic and pulmonary circulation.
• What happens to cardiac function if the atrioventricular node malfunctions?
  • If the atrioventricular node malfunctions, it can lead to various arrhythmias or heart blocks. In some cases, this may result in complete dissociation between atrial and ventricular contractions, meaning that they beat independently rather than in sync. This can severely impair cardiac output and blood circulation throughout the body, highlighting the AV node's critical function in maintaining orderly electrical conduction in the heart.
• Evaluate how electrical conduction through the atrioventricular node impacts overall cardiovascular health and function.
  • Electrical conduction through the atrioventricular node is essential for effective cardiovascular health and function. The proper delay induced by this node allows for optimal ventricular filling, which maximizes stroke volume and cardiac output. If conduction is impaired due to disease or dysfunction of the AV node, it can lead to inefficient heart rhythms that compromise blood flow to vital organs. Thus, understanding AV node function is critical when assessing overall heart health and managing conditions like heart block or arrhythmias.

Related terms

Sinoatrial Node: The sinoatrial (SA) node is known as the heart's natural pacemaker, generating electrical impulses that initiate each heartbeat.

Bundle of His: The Bundle of His is a collection of heart muscle cells that transmit electrical impulses from the AV node to the ventricles, facilitating coordinated contraction.

Cardiac Cycle: The cardiac cycle refers to the sequence of events in a single heartbeat, including atrial and ventricular contraction and relaxation.