Summary
The SA node, AV node and Purkinje fibres coordinate heartbeat electrical signals seen on an ECG.
In depth
SA node (pacemaker, about 70 beats per minute) depolarises atria; delay at AV node lets ventricles fill; bundle of His and Purkinje fibres rapidly spread excitation. ECG: P wave (atrial depolarisation), QRS complex (ventricular depolarisation) and T wave (repolarisation).
The AV delay lets ventricles fill. Autonomic input adjusts rate. Arrhythmias arise from conduction faults.
Key idea: electrical activity precedes mechanical contraction.
The sinoatrial node (in the right atrium) has cells that depolarise spontaneously through funny current (If) and calcium channels, setting the rhythm; the autonomic nervous system modulates the rate (vagus slows, sympathetic speeds). The AV node delays about 0.1 s, then impulses spread via the bundle of His, left and right bundle branches and Purkinje fibres, causing coordinated ventricular contraction from apex upward. Gap junctions in intercalated discs allow rapid spread.
The ECG records electrical activity: P wave (atrial depolarisation), QRS complex (ventricular depolarisation) and T wave (repolarisation). Arrhythmias include atrial fibrillation (chaotic atrial activity, stroke risk), heart block and ventricular fibrillation (fatal unless defibrillated). Pacemakers replace faulty nodes.
Example: a defibrillator delivers a shock to reset the heart's electrical activity.
Frequently asked questions
What is Cardiac Conduction System?
The SA node, AV node and Purkinje fibres coordinate heartbeat electrical signals seen on an ECG.
Which area of biology covers Cardiac Conduction System, and how advanced is it?
Cardiac Conduction System is one of the 51 topics in Human Physiology. It is rated Advanced, so it suits learners who want specialist depth. Related topics in this area include Frank-Starling Law, Cardiac Cycle, Muscular System.
Can you give an example of Cardiac Conduction System?
Artificial pacemakers substitute for a failing SA node.
What should I learn before Cardiac Conduction System?
Work through the Beginner topics in Human Physiology first, such as Homeostasis, Tissues and Organs, Skeletal System, then return to Cardiac Conduction System. Advanced topics assume the Intermediate vocabulary.
What topics are related to Cardiac Conduction System?
The closest topics to Cardiac Conduction System are Frank-Starling Law, Cardiac Cycle, Muscular System, Circulatory System. Comparing them side by side is a good way to see how the ideas connect.
How can I check that I understand Cardiac Conduction System?
Read the summary and the in-depth section, then use the quick check on the interactive lesson for Cardiac Conduction System. To practise the whole of Human Physiology, use the Human Physiology quiz.
How is Cardiac Conduction System different from Frank-Starling Law?
Cardiac Conduction System: The SA node, AV node and Purkinje fibres coordinate heartbeat electrical signals seen on an ECG. Frank-Starling Law: Greater ventricular filling stretches the heart and increases the force of the next contraction. Read both side by side and note what each one explains.
How should I study Cardiac Conduction System step by step?
First, read the summary and write the definition in your own words. Second, read the in-depth section and note any example. Third, compare it with Frank-Starling Law and explain the difference aloud. Finally, take the Human Physiology quiz and come back to this page for any question you miss.