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Conduction System of the Heart

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:...

Conduction System of the Heart

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...

Electrophysiology of Normal Cardiac Rhythm

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...

Cardiac Action Potential

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

Electrical Synapses

Electrical Synapses

Electrical synapses found in all nervous systems play important and unique roles. In these synapses, the presynaptic and postsynaptic membranes are very close together (3.5 nm) and are actually physically connected by channel proteins forming gap junctions.
Gap junctions allow the current to pass directly from one cell to the next. In contrast, in the chemical synapse, the neurotransmitters carry the information through the synaptic cleft from one neuron to the next. They consist of two...

Correlation between ECG and Cardiac Cycle

Correlation between ECG and Cardiac Cycle

The electrical signals recorded on an electrocardiogram (ECG) occur before the mechanical processes of contraction and relaxation during the cardiac cycle.
A cardiac action potential originates in the SA node and spreads throughout the atria and the AV node in approximately 0.03 seconds. This results in the P wave in an ECG and triggers atrial contraction. The action potential is then briefly slowed at the AV node, allowing the atria to contract and fill the ventricles with blood before...

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Ephaptic coupling and the source-sink effect of cardiac conduction.

Jingwu Pan¹, Peter Hanna¹, Alan Garfinkel¹

¹Department of Medicine, David Geffen School of Medicine, University of California, Los Angeles, CA, USA.

The Journal of Physiology

|March 26, 2026

Summary

Ephaptic coupling, unlike gap junction coupling, does not require a critical number of cells for cardiac conduction, eliminating the source-sink effect. The interaction between ephaptic and gap junction coupling influences conduction and may impact heart rhythm disorders.

Keywords:

cardiac conduction ephaptic coupling gap junction coupling intercalated disc source–sink effect

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Published on: June 16, 2020

Area of Science:

Cardiovascular Physiology
Computational Biology
Biophysics

Background:

Cardiac electrical conduction relies primarily on gap junction coupling, involving a 'source-sink effect' where a minimum number of excited cells are needed.
The influence of ephaptic coupling (electrical field effects) on this source-sink effect in cardiac tissue remains largely unexplored.

Purpose of the Study:

To investigate the impact of ephaptic coupling, both independently and in conjunction with gap junction coupling, on the cardiac source-sink effect.
To analyze how different depolarization triggers (external stimulation, delayed afterdepolarization, automaticity) interact with ephaptic and gap junction coupling.

Main Methods:

Computer simulations using a one-dimensional cardiac myocyte model with a cleft.
Incorporation of junctional ion channel distributions and varying cleft widths.
Analysis of conduction triggered by different types of cellular depolarization.

Main Results:

Pure ephaptic coupling eliminates the source-sink effect, requiring only one stimulated cell for conduction.
Increased gap junction conductance elevates the number of cells needed for conduction, consistent with the source-sink theory.
Complex dependencies of the source-sink effect on cleft width arise from ephaptic attenuation of sodium current and enhancement of potassium current.

Conclusions:

Ephaptic coupling and intercellular cleft width play significant, non-trivial roles in cardiac conduction dynamics and the source-sink effect.
These findings suggest that altered gap junctions and cleft structures in disease states could impact arrhythmogenesis through modified ephaptic interactions.