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Related Concept Videos

Conduction System of the Heart01:19

Conduction System of the Heart

Autorhythmicity is a term that refers to the heart's inherent ability to generate electrical signals and instigate muscle contractions. This self-regulating conduction system within the heart consists of two key components: the pacemaker cells and specialized conducting cells.
The pacemaker cells are located in two primary nodes: the sinoatrial (SA) node and the atrioventricular (AV) node. The SA node pacemaker cells can autonomously depolarize, triggering an action potential that leads to the...
Conduction System of the Heart01:20

Conduction System of the Heart

The cardiac conduction system produces and transmits electrical impulses that prompt myocardial contraction, ensuring efficient heart function. This intricate system ensures that the heart beats in a coordinated and efficient manner, beginning with the atria and then the ventricles. The conduction system optimizes cardiac output by maintaining this precise sequence, which is crucial for adequate blood circulation.
This system relies on the unique properties of nodal and Purkinje cells:...
Electrophysiology of Normal Cardiac Rhythm01:19

Electrophysiology of Normal Cardiac Rhythm

The normal cardiac rhythm is a synchronized electrical activity that facilitates the regular and coordinated contraction of the heart muscle. This process is essential for efficient blood circulation throughout the body. The fundamental elements involved in establishing and maintaining this rhythm include the unique electrical properties of cardiac muscle cells, the sinoatrial (SA) node's pacemaker function, the specialized conducting system, and the ionic mechanisms underlying each phase of...
Cardiac Action Potential01:30

Cardiac Action Potential

Cardiac action potentials are essential for proper heart function, enabling the rhythmic contractions needed for adequate blood circulation. Nodal cells and Purkinje fibers, specialized for electrical conduction, generate these action potentials.
The cardiac action potential process involves a series of phases characterized by the movement of ions across the cardiac cell membranes, leading to the depolarization and repolarization of the cardiac myocytes.
Ionic Basis of Cardiac Action Potentials
Mechanism of Cardiac Arrhythmias01:28

Mechanism of Cardiac Arrhythmias

Arrhythmias are irregular heart rhythms occurring when the heart's electrical impulses become abnormal. These disturbances can lead to various symptoms, depending on their severity and the underlying cause. Some common factors contributing to arrhythmias include hypoxia, ischemia, electrolyte imbalances, excessive catecholamine exposure, drug toxicity, and muscle overstretching. Arrhythmias can be classified into two main types based on the rate and site of origin of abnormal heart rhythms.
The Cardiac Cycle01:13

The Cardiac Cycle

The heart beats rhythmically in a sequence called the cardiac cycle—a rapid coordination of contraction (systole) and relaxation (diastole).
The Process
Electrical signals—sent from the sinoatrial (SA) node in the right atrial wall to the atrioventricular (AV) node between the right atrium and right ventricle—cause both atria to simultaneously contract. When the signal reaches the AV node, it pauses for approximately a tenth of a second, allowing the atria to contract and empty blood into the...

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Related Experiment Video

Updated: Jun 3, 2026

Microelectrode Array Recording of Sinoatrial Node Firing Rate to Identify Intrinsic Cardiac Pacemaking Defects in Mice
09:20

Microelectrode Array Recording of Sinoatrial Node Firing Rate to Identify Intrinsic Cardiac Pacemaking Defects in Mice

Published on: July 5, 2021

Pacemaker activity and ionic currents in mouse atrioventricular node cells.

Laurine Marger1, Pietro Mesirca, Jacqueline Alig

  • 1CNRS, UMR-5203, Institut de Génomique Fonctionnelle, Département de Physiologie, Montpellier, France.

Channels (Austin, Tex.)
|March 17, 2011
PubMed
Summary
This summary is machine-generated.

The atrioventricular node (AVN) can initiate heartbeats, but its ionic basis is unclear. This study found that reduced hyperpolarization-activated current (If) and L-type calcium current (ICa,L) contribute to slower AVN pacemaker activity compared to the sino-atrial node.

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Area of Science:

  • Cardiology
  • Electrophysiology
  • Molecular Biology

Background:

  • The sino-atrial node (SAN) initiates heartbeats, but the atrioventricular node (AVN) can compensate during SAN failure.
  • The ionic mechanisms underlying AVN automaticity are not fully understood.

Purpose of the Study:

  • To characterize the pacemaker activity and ionic currents in mouse AVN cells (AVNCs).
  • To compare AVNCs' electrophysiological properties with sino-atrial node pacemaker cells (SANCs).

Main Methods:

  • Patch-clamp electrophysiology was used to record ionic currents in AVNCs and SANCs.
  • Pharmacological agents like tetrodotoxin (TTX), isradipine, and ZD-7228 were used to block specific currents.
  • Pacemaker activity was measured under control conditions and in the presence of isoproterenol (ISO).

Main Results:

  • AVNCs exhibited slower pacemaking than SANCs, even with ISO.
  • Blockade of sodium current (INa) and L-type calcium current (ICa,L) abolished AVNC pacemaking.
  • AVNCs showed lower densities of If and ICa,L, but higher IKr compared to SANCs.
  • Inhibition of If reduced AVNC pacemaker activity by 16%.

Conclusions:

  • The intrinsic slower pacemaking of AVNCs is attributed to lower If and ICa,L densities and higher IKr expression compared to SANCs.
  • Both INa and ICa,L are crucial for AVNC automaticity.
  • If plays a significant role in AVNC pacemaking.