voltage-gated potassium channel activity involved in atrial cardiac muscle cell action potential repolarization

Definition

Target type: molecularfunction

Enables the transmembrane transfer of a potassium ion by a voltage-gated channel through the plasma membrane of an atrial cardiomyocyte contributing to the repolarization phase of an action potential. A voltage-gated channel is a channel whose open state is dependent on the voltage across the membrane in which it is embedded. [GOC:BHF, GOC:mtg_cardiac_conduct_nov11]

Voltage-gated potassium channels (Kv channels) are integral to the repolarization phase of the atrial cardiac muscle cell action potential. They are transmembrane proteins that form ion channels, selectively allowing potassium ions (K+) to flow across the cell membrane. During the plateau phase of the action potential, when sodium channels close and calcium channels open, potassium channels begin to open, allowing K+ to flow out of the cell. This outward movement of K+ counteracts the inward flow of calcium, leading to a decrease in the membrane potential. As the outward potassium current increases, the membrane potential rapidly declines, resulting in the repolarization phase.

Several types of Kv channels are involved in atrial repolarization, each contributing to different aspects of the process:

1. **Rapidly activating delayed rectifier potassium channels (Kv1.5):** These channels open rapidly upon membrane depolarization and contribute to the initial repolarization phase. They are responsible for the rapid decline in membrane potential after the plateau phase.

2. **Slowly activating delayed rectifier potassium channels (Kv2.1):** These channels open more slowly than Kv1.5 channels and contribute to the later stages of repolarization. They help maintain the repolarized state and prevent premature depolarization.

3. **Transient outward potassium channels (Kv4.2/4.3):** These channels open briefly during the early repolarization phase and contribute to the initial repolarization slope.

4. **Ultra-rapidly activating delayed rectifier potassium channels (Kv1.4):** These channels are found in atrial myocytes and contribute to the rapid repolarization phase.

5. **Inward rectifier potassium channels (Kir2.1):** These channels open at hyperpolarized membrane potentials and contribute to the resting membrane potential. They also help to regulate the duration of the action potential by modulating the inward potassium current.

The coordinated opening and closing of these different Kv channels is essential for the normal repolarization of the atrial action potential. Disruptions in Kv channel function can lead to abnormal repolarization, which can increase the risk of atrial arrhythmias. '
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Proteins (4)

Compounds (60)