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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 of...

Cardiac Action Potential

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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.
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Mechanism of Cardiac Arrhythmias

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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.

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...

Specialized Characteristics of Cardiac Muscles

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The primary role of cardiac muscles is to propel blood throughout the cardiovascular system. The cardiac muscle cells, or cardiomyocytes, exhibit specialized characteristics that allow them to perform this function.
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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:...

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Related Experiment Video

Updated: Jun 1, 2026

Assessment of Myofilament Ca2+ Sensitivity Underlying Cardiac Excitation-contraction Coupling

Assessment of Myofilament Ca²⁺ Sensitivity Underlying Cardiac Excitation-contraction Coupling

Published on: August 1, 2016

Local control in cardiac E-C coupling.

M B Cannell¹, Cherrie H T Kong

¹School of Physiology & Pharmacology, University of Bristol, Medical Sciences Building, University Walk, Bristol, BS8 1TD, UK. mark.cannell@bristol.ac.uk

Journal of Molecular and Cellular Cardiology

|May 19, 2011

Summary

This summary is machine-generated.

Local control theory explains cardiac calcium release by spatially limiting regeneration through stochastic recruitment of calcium release units (CRUs). This ensures stable heart contraction without compromising sensitivity.

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Published on: May 22, 2018

Area of Science:

Cardiology
Molecular Biology
Cell Physiology

Background:

The calcium-induced calcium release (CICR) hypothesis explains cardiac excitation-contraction coupling.
Regeneration in CICR presents challenges in controlling calcium release and force production.

Purpose of the Study:

To explain how local control theory addresses regeneration issues in CICR.
To elucidate the spatial uncoupling of calcium release units (CRUs) and their role in graded calcium release.
To review mechanisms for CRU calcium release termination and suggest novel functions for sarcoplasmic reticulum calcium modulation.

Main Methods:

Theoretical explanation of local control mechanisms in cardiac excitation-contraction coupling.
Analysis of the spatial relationship between CRUs and their impact on calcium dynamics.
Review of potential mechanisms for terminating calcium release from CRUs.

Main Results:

Local control theory explains graded calcium release by spatially limiting regeneration through the stochastic recruitment of CRUs.
The distance between CRUs partially uncouples them, limiting regenerative gain and ensuring stability.
High local calcium levels near the surface membrane activate RyRs, while diffusion limits spread to adjacent CRUs.

Conclusions:

Local control theory provides a framework for understanding cardiac calcium release and force production.
Modulation of RyR gating may regulate sarcoplasmic reticulum calcium levels for metabolic functions beyond contractility.
Further research is needed to clarify the termination mechanisms of CRU calcium release.