Wave of Excitation: A Comprehensive Review
Introduction
The wave of excitation is a concept in cardiac physiology that describes the mechanism by which the electrical impulse from the sinoatrial node spreads throughout the myocardium to initiate the contraction of heart muscle cells. This wave of excitation is generated by the sequential activation of gap junctions, which connect adjacent myocardial cells and allow for the passage of electrical current and the propagation of the impulse. This article provides an overview of the wave of excitation, its components, and its role in cardiac contraction.
Components of the Wave of Excitation
The wave of excitation is composed of three distinct components: the electrical conduction system, the gap junctions, and the myocardial cells. The electrical conduction system consists of the sinoatrial node, atrioventricular node, and the Purkinje fibers. The sinoatrial node is the primary pacemaker of the heart and generates the electrical impulse that initiates the wave of excitation. The atrioventricular node and the Purkinje fibers serve as pathways for the electrical impulse to travel from the atria to the ventricles.
The gap junctions are specialized intercellular channels that allow for the passage of electrical current and the propagation of the electrical impulse throughout the myocardium. These channels are composed of connexins, which are proteins that form the walls of the gap junctions. The connexins allow for the passage of ions such as calcium and sodium, which are essential for the propagation of the electrical impulse.
The myocardial cells are the muscle cells of the heart that are responsible for contraction. These cells contain specialized contractile proteins that, when stimulated by the electrical impulse, generate the force necessary for the heart to pump blood.
Role of the Wave of Excitation
The wave of excitation is essential for the contraction of the heart. The electrical impulse generated by the sinoatrial node is propagated through the gap junctions to the myocardial cells, which then generate the force necessary for the heart to pump blood. The wave of excitation is also responsible for the sequential contraction of the atria and ventricles that is necessary for the efficient pumping of blood.
Conclusion
The wave of excitation is an essential component of cardiac physiology. Its components, the electrical conduction system, gap junctions, and myocardial cells, are necessary for the propagation of the electrical impulse and the subsequent contraction of the heart. The wave of excitation is responsible for the efficient pumping of blood throughout the body and is critical for life.
References
Chen, P. S., & Lederer, W. J. (2006). Gap junctions and electrical coupling: The basis of cardiac conduction. Physiological Reviews, 86(1), 117–154. doi:10.1152/physrev.00011.2005
Khan, M. U., & Kléber, A. G. (2012). Cardiac excitation-contraction coupling. Compr Physiol, 2(1), 681–715. doi:10.1002/cphy.c100063
Webb, R. C., & Forbush, B. (2009). The heart and its electrical conduction system. In Clinical Cardiology: A Comprehensive Textbook (pp. 11–19). Philadelphia, PA: Lippincott Williams & Wilkins.