Conduction System of the Heart


The cardiac muscle beats with an intrinsic rhythm. This permits the heart to beat without extrinsic stimulation. The heart begins its rhythm and continues its rhythm, basically until something interrupts it. Interconnecting cardiac muscle tissue which is specially designed to continue the rhythm of the heart’s contraction creates the heart’s system of conduction. These strands of cardiac muscle tissue keep the heart beating in the rhythm that it begins with without interruption through coordinating action. The cardiac cycle refers to the process which fills and empties the individual chambers of the heart. The system of the heart’s conduction enables this cycle to continue without interruption.


Via a complex system of cardiac energy, which is the generation and distribution of electrical impulses, the muscle tissue is “in charge” of the rate the heart beats. The heart’s conduction system is comprised of various components. The sinoatrial node is the body’s natural pace maker. It is positioned along the posterior wall of the right atrium. More specifically, it is positioned where the superior vena cava creates its connection with the heart. The electrical impulses generated by the sinoatrial node initiates the entire cardiac cycle. The electrical impulses which the sinoatrial node is responsible for creating affects the right and left atria and controls their contraction. By controlling the unison contraction, the sinoatrial node keeps the heart beating with its depolarization rate of 70 to 80 times per minute. The electrical impulses are then distributed to the atrioventricular node.


Conduction System of the Heart
Image: Conduction System Of The Heart

The atrioventricular node is positioned in the inferior section of the interatrial septum. The atrioventricular bundle then picks up the following electrical impulses which is positioned on the tops of the interatrial bundle. The atrioventricular bundle then branches off into two separate bundles, the right and the left. Each individual branch runs ad infinitum with conduction myofibers that are just internal of the ventricular wall. The unified ventricular contraction is caused by the stimulation of these fibers. Systole is the term given to the simultaneous contraction of the ventricles.

Systolic pressure inside the arteries is produced by the conjunction of systole, tension of the supple fibers, and the contraction of the smooth muscle within the systemic arteries. Diastole is the term given to the action of ventricular relaxation. Diastolic pressure within the arteries is measured when the ventricles are relaxed.


Despite the heart’s ability to maintain its self generated beat, there are times when the heart needs to adjust in response to the varying demands of the physical human body. This is controlled by intervention of the automic nervous system. Both the atrioventricular node and the sinoatrial node are innervated with sympathetic and parasympathetic innervation. When the heart responds to the increased needs of the body, as well as its own increased need, this is known as sympathetic stimulation. It is marked by the acceleration of the heart rate and dilation of the coronary arteries. Parasympathetic stimulation refers to the heart’s ability to slow down in response the decreased needs of both the body and the heart. Fibers from the cervical as well as the upper thoracic ganglia are responsible for the sympathetic innervation. Branches of the vagus nerves stimulate the parasympathetic innervation. The sinoatrial node is innervated by the branches coming from the right vagus nerves while the branches from the left vagus nerves are responsible for the innervation of the atrioventricular node.
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