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Related Concept Videos

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
The Resting Membrane Potential01:21

The Resting Membrane Potential

Overview
Action Potential: Phases of Stimulation01:28

Action Potential: Phases of Stimulation

The action potential is a complex electrical event that occurs in excitable cells, such as neurons and muscle cells. It consists of several distinct phases, each with specific characteristics.
Resting Phase:
In this phase, the cell's membrane is at its resting potential, typically around -70 millivolts (mV) for neurons. Inside the cell, there is a higher concentration of potassium ions (K+) and a lower concentration of sodium ions (Na+). Voltage-gated sodium channels are closed, and...
Resting Membrane Potential01:24

Resting Membrane Potential

The relative difference in electrical charge, or voltage, between the inside and the outside of a cell membrane, is called the membrane potential. It is generated by differences in permeability of the membrane to various ions and the concentrations of these ions across the membrane.
The Inside of a Neuron is More Negative
The membrane potential of a cell can be measured by inserting a microelectrode into a cell and comparing the charge to a reference electrode in the extracellular fluid. The...
Resting Membrane Potential01:24

Resting Membrane Potential

The relative difference in electrical charge, or voltage, between the inside and the outside of a cell membrane, is called the membrane potential. It is generated by differences in permeability of the membrane to various ions and the concentrations of these ions across the membrane.
The Inside of a Neuron is More Negative
The membrane potential of a cell can be measured by inserting a microelectrode into a cell and comparing the charge to a reference electrode in the extracellular fluid. The...
Antiarrhythmic Drugs: Class I Agents as Sodium Channel Blockers01:22

Antiarrhythmic Drugs: Class I Agents as Sodium Channel Blockers

Class I antiarrhythmic drugs are used to treat various types of arrhythmias or irregular heart rhythms. These drugs block the sodium (Na+) channels in the cardiac cells, thereby affecting the movement of electrical impulses across the heart. Class I antiarrhythmic drugs are divided into three subgroups: Class IA, Class IB, and Class IC, each with distinct mechanisms of action and effects on the heart.
Class 1A Antiarrhythmic Drugs: These drugs work by moderately blocking sodium channels,...

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Related Experiment Video

Updated: Jun 21, 2026

Recapitulation of an Ion Channel IV Curve Using Frequency Components
10:14

Recapitulation of an Ion Channel IV Curve Using Frequency Components

Published on: February 8, 2011

Molecular determinants of repolarization time.

Bernard Swynghedauw1, Gaele Aubert

  • 1U572-INSERM Hôpital Lariboisière, Paris, France.

Experimental and Clinical Cardiology
|July 31, 2009
PubMed
Summary
This summary is machine-generated.

Repolarization time (RT) is determined by ion currents and transmural gradients. Genetic mutations and drugs affecting potassium channels, particularly I(Kr), cause long QT syndrome, while reduced I(tO) impacts RT in heart failure.

Keywords:
Cardiac geneticsCardiac hypertrophyIon channelsLong QTSudden death

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Modeling Biological Membranes with Circuit Boards and Measuring Electrical Signals in Axons: Student Laboratory Exercises
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Isolation of Atrial Myocytes from Adult Mice
08:34

Isolation of Atrial Myocytes from Adult Mice

Published on: July 25, 2019

Area of Science:

  • Cardiology
  • Molecular Biology
  • Electrophysiology

Background:

  • Cardiac action potential duration relies on a balance of ion currents.
  • Transmural gradients (endo/epicardial, apex/base) influence in vivo repolarization time (RT).
  • QT dispersion on body surface ECGs doesn't fully capture spatial RT heterogeneity.

Purpose of the Study:

  • To review molecular determinants of repolarization time (RT) in normal and disease states.
  • To analyze genetic and drug-induced causes of long QT syndrome.
  • To explore RT alterations in cardiac hypertrophy and heart failure.

Main Methods:

  • Analysis of recent data on molecular determinants of repolarization time.
  • Review of ion channel function and mutations related to QT interval.
  • Examination of RT changes in pathological cardiac conditions.

Main Results:

  • Inherited long QT syndrome results from mutations affecting sodium and potassium currents (I(Kr)).
  • Drug-induced long QT is linked to potassium channel blockers, primarily targeting I(Kr).
  • Prolonged RT in hypertrophy/heart failure is associated with decreased I(tO) channel density and potential reversal of transmural gradients.

Conclusions:

  • Molecular mechanisms involving ion channel function are crucial for normal and abnormal repolarization.
  • Understanding these determinants is key for managing long QT syndromes and cardiac dysfunction.
  • Reduced I(tO) plays a significant role in repolarization abnormalities during cardiac hypertrophy and failure.