Pacemaker current

Pacemaker Current

Chemical structure of Ivabradine, a drug that affects the pacemaker current.

The pacemaker current, also known as the "funny" current (I_f), is a crucial component of the electrical activity in the heart, particularly in the sinoatrial node (SAN), which is the natural pacemaker of the heart. This current is responsible for the automaticity of the heart, allowing it to beat rhythmically without external stimuli.

Mechanism

The pacemaker current is primarily carried by sodium (Na⁺) and potassium (K⁺) ions through hyperpolarization-activated cyclic nucleotide-gated (HCN) channels. These channels are activated during the hyperpolarization phase of the cardiac action potential, leading to a slow depolarization that triggers the next action potential. This process is essential for the generation of spontaneous rhythmic activity in the heart.

Role in Cardiac Function

The pacemaker current plays a vital role in setting the pace of the heart rate. It is modulated by the autonomic nervous system, with sympathetic stimulation increasing the current and parasympathetic stimulation decreasing it. This modulation allows the heart to adjust its rate in response to physiological demands.

Pharmacological Modulation

Ivabradine is a drug that specifically inhibits the pacemaker current by blocking the HCN channels. It is used clinically to reduce heart rate in conditions such as angina pectoris and heart failure. By selectively targeting the pacemaker current, Ivabradine provides a means to control heart rate without affecting other cardiac functions.

Clinical Significance

Abnormalities in the pacemaker current can lead to arrhythmias, such as bradycardia or tachycardia. Understanding the pacemaker current is crucial for developing treatments for these conditions. Additionally, research into the genetic and molecular basis of the pacemaker current continues to provide insights into its role in cardiac health and disease.

Related Pages

• Sinoatrial node
• Cardiac action potential
• Heart rate
• Arrhythmia
• Ivabradine