Cardiac action potential

Cardiac action potential is the process by which the heart's electrical system regulates the heart rate and rhythm. This process is crucial for maintaining a steady and regular heartbeat. The cardiac action potential is a complex process that involves several stages and numerous ion channels and proteins.

Shapes of the cardiac action potential in the heart

Overview

The cardiac action potential is initiated in the sinoatrial node (SA node), the heart's natural pacemaker. The SA node generates an electrical impulse that spreads through the heart, causing the heart muscle to contract and pump blood. This electrical impulse is the cardiac action potential.

Phases of the Cardiac Action Potential

The cardiac action potential consists of five phases, numbered 0 through 4.

Phase 0

Phase 0 is the rapid depolarization phase. During this phase, voltage-gated sodium channels open, allowing sodium ions to flow into the cell. This causes the cell's membrane potential to become more positive.

Phase 1

Phase 1 is the initial repolarization phase. During this phase, the sodium channels close and potassium channels open, allowing potassium ions to flow out of the cell. This causes the cell's membrane potential to become more negative.

Phase 2

Phase 2 is the plateau phase. During this phase, calcium channels open, allowing calcium ions to flow into the cell. This balances the outflow of potassium ions, causing the cell's membrane potential to plateau.

Phase 3

Phase 3 is the rapid repolarization phase. During this phase, the calcium channels close and more potassium channels open. This causes the cell's membrane potential to become more negative, returning to its resting state.

Phase 4

Phase 4 is the resting phase. During this phase, the cell's membrane potential is maintained at a steady negative value until the next cardiac action potential is initiated.

Role in Heart Function

The cardiac action potential plays a crucial role in regulating the heart's function. It ensures that the heart beats in a regular and coordinated manner, allowing it to effectively pump blood throughout the body. Abnormalities in the cardiac action potential can lead to arrhythmias, which are irregular heart rhythms that can be life-threatening.

See Also

• Electrocardiogram
• Cardiac cycle
• Heart rate
• Arrhythmia