Heart; conduction system. 1. SA node. 2. AV node. 3. Bundle of His. 8. Septum
Sinoatrial node shown at 1. The rest of the conduction system of the heart is shown in blue.
Image showing the conduction system of the heart. The AV node is labelled 2.
Overview of the system of electrical conduction which maintains the rhythmical contraction of the heart
Figure 2: Low magnification stained image of the SA node (center-right on image) and its surrounding tissue. The SA node surrounds the sinoatrial nodal artery, seen as the open lumen. Cardiac muscle cells of the right atrium can be seen to the left of the node, and fat tissue to the right.
Isolated heart conduction system showing atrioventricular node
Figure 3: Sinoatrial node action potential waveform, outlining major ion currents involved (downward deflection indicates ions moving into the cell, upwards deflection indicates ions flowing out of the cell).
Principle of ECG formation. Note that the red lines represent the depolarization wave, not bloodflow.
Schematic representation of the atrioventricular bundle
Different wave shapes generated by different parts of the heart's action potential

The electrical conduction system of the heart transmits signals generated usually by the sinoatrial node in the heart to cause contraction of the heart muscle.

- Electrical conduction system of the heart

The atrioventricular node or AV node electrically connects the heart's atria and ventricles to coordinate beating in the top of the heart; it is part of the electrical conduction system of the heart.

- Atrioventricular node

The pacemaking signal generated in the sinoatrial node travels through the right atrium to the atrioventricular node, along the Bundle of His and through bundle branches to cause contraction of the heart muscle.

- Electrical conduction system of the heart

These cells can produce an electrical impulse (action potential) that travels through the electrical conduction system of the heart, causing it to contract.

- Sinoatrial node

A wave of excitation spreads out from the sinoatrial node through the atria along specialized conduction channels.

- Atrioventricular node

Other cells within the heart (including the Purkinje fibers and atrioventricular node) can also initiate action potentials; however, they do so at a slower rate and therefore, if the SA node is functioning properly, its action potentials usually override those that would be produced by other tissues.

- Sinoatrial node
Heart; conduction system. 1. SA node. 2. AV node. 3. Bundle of His. 8. Septum

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Muscular organ in most animals.

Muscular organ in most animals.

Human heart during an autopsy
Computer-generated animation of a beating human heart
The human heart is in the middle of the thorax, with its apex pointing to the left.
Heart being dissected showing right and left ventricles, from above
Frontal section showing papillary muscles attached to the tricuspid valve on the right and to the mitral valve on the left via chordae tendineae.
Layers of the heart wall, including visceral and parietal pericardium
The swirling pattern of myocardium helps the heart pump effectively
Arterial supply to the heart (red), with other areas labelled (blue).
Autonomic innervation of the heart
Development of the human heart during the first eight weeks (top) and the formation of the heart chambers (bottom). In this figure, the blue and red colors represent blood inflow and outflow (not venous and arterial blood). Initially, all venous blood flows from the tail/atria to the ventricles/head, a very different pattern from that of an adult.
Blood flow through the valves
The cardiac cycle as correlated to the ECG
The x-axis reflects time with a recording of the heart sounds. The y-axis represents pressure.
Transmission of a cardiac action potential through the heart's conduction system
Conduction system of the heart
The prepotential is due to a slow influx of sodium ions until the threshold is reached followed by a rapid depolarization and repolarization. The prepotential accounts for the membrane reaching threshold and initiates the spontaneous depolarization and contraction of the cell; there is no resting potential.
3D echocardiogram showing the mitral valve (right), tricuspid and mitral valves (top left) and aortic valve (top right).
The closure of the heart valves causes the heart sounds.
Cardiac cycle shown against ECG
Heart and its blood vessels, by Leonardo da Vinci, 15th century
Animated heart
Elize Ryd making a heart sign at a concert in 2018
The tube-like heart (green) of the mosquito Anopheles gambiae extends horizontally across the body, interlinked with the diamond-shaped wing muscles (also green) and surrounded by pericardial cells (red). Blue depicts cell nuclei.
Basic arthropod body structure – heart shown in red
The human heart viewed from the front
The human heart viewed from behind
The coronary circulation
The human heart viewed from the front and from behind
Frontal section of the human heart
An anatomical specimen of the heart
Heart illustration with circulatory system
Animated Heart 3d Model Rendered in Computer

The heart pumps blood with a rhythm determined by a group of pacemaker cells in the sinoatrial node.

These generate a current that causes the heart to contract, traveling through the atrioventricular node and along the conduction system of the heart.