Ionic events responsible for the cardiac resting and action potential

Area of Science:

• Cardiology
• Electrophysiology
• Molecular Biology

Background:

• The cardiac action potential exhibits unique features like a plateau and pacemaking.
• Ionic fluxes through gated membrane channels are key determinants of its shape.

Purpose of the Study:

• To review experimental data on ionic fluxes and their role in shaping the cardiac action potential.
• To elucidate the contribution of various ion channels and transport systems to cardiac electrophysiology.

Main Methods:

• Review of experimental data on ionic fluxes through cardiac membrane channels.
• Analysis of voltage- and time-dependent properties of ion channels.
• Examination of coupled transport mechanisms in myocardium.

Main Results:

• Sodium ion (Na+) and calcium ion (Ca2+) channels contribute to depolarization and plateau phases.
• Two distinct potassium ion (K+) transport systems regulate K+ flux at rest and during the action potential plateau.
• Electrogenic Na+ pump and Na+-Ca2+ counter-transport maintain intracellular Na+ and Ca2+ concentrations.

Conclusions:

• Ionic fluxes through gated channels are primary determinants of the cardiac action potential.
• Further research is needed to quantitatively reconstruct the cardiac action potential by detailing channel and carrier mechanisms.