Heart's Electrical System and ECG

Also called

ECG · electrocardiogram · electrocardiograph · heart electrical system · conduction system of the heart · SA node · sinoatrial node · pacemaker · AV node · atrioventricular node · bundle of His · Purkinje fibres · P wave · QRS complex · T wave · cardiac cycle · heartbeat · myogenic heart · हृदय · हृदय स्पंदन · ईसीजी

Topics

• The human heart is myogenic: each beat starts in the sino-atrial (SA) node, the pacemaker, about 72 times a minute.
• The impulse from the SA node spreads over both atria, which contract together; on the ECG this is the P wave.
• The AV node passes the impulse on after a short delay, so the atria empty before the ventricles contract.
• From the AV node the bundle of His and its two branches carry the impulse down the septum to the Purkinje fibres.
• Purkinje fibres spread the impulse through the ventricle walls and both ventricles contract: the QRS complex.
• The T wave marks the ventricles returning to their resting state (repolarisation) before the next beat.
• One cardiac cycle, from one P wave to the next, lasts about 0.8 s: roughly 72 beats a minute at rest.
• A doctor reads the shape and spacing of P, QRS and T on an ECG to spot a fast, slow or irregular heartbeat.

About this model

A GLB file of about 906 KB, shown in Lably's 3D viewer and, on a phone, placed in your room with AR. Credit: Model, science and animation: Lably (built procedurally with three.js; no downloaded meshes). | CC BY 4.0. Original geometry and animation made for Lably.

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