The heart is its own electrical generator
In short: Unlike most muscles, the heart doesn't wait for a signal from the brain to beat. This video explores the myogenic nature of cardiac muscle and the specific electrical pathway that coordinates every contraction.
The heart functions as a myogenic organ, meaning it generates its own rhythmic electrical impulses. The process begins at the sinoatrial node (SAN), which acts as the natural pacemaker. From there, the impulse travels to the atrioventricular node (AVN), where a crucial delay occurs before the signal moves through the bundle of His to the apex. Finally, the Purkinje fibres ensure the ventricles contract effectively.
The video also covers how these electrical events are captured via electrocardiograms (ECGs). By interpreting the P wave, QRS complex, and T wave, clinicians can identify various abnormalities, including tachycardia, bradycardia, and atrial fibrillation. Note that exam requirements for ECGs vary significantly by board, with AQA and CIE excluding them from the syllabus.
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Sources
- Summary by Intellect · source: A-Level Biology - How the Heartbeat is Controlled - Pathway of Excitation | ECGs (2027/28 exams)
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