Conducting system of the heart.
Conducting System of the Heart
The heart's conducting system is a network of specialized cells that generate and transmit electrical impulses to coordinate heartbeats, ensuring efficient blood pumping. It's like the heart's wiring, allowing synchronized contractions. Below is a concise overview, easy to follow, with real physiological data based on human anatomy.
Key Components
Sinoatrial (SA) Node: The heart's natural pacemaker, located in the right atrium's upper wall. It initiates impulses.
Real data: Fires at 60–100 times per minute (resting heart rate in adults); impulse speed ~0.05 m/s.
Atrioventricular (AV) Node: Acts as a relay station in the lower right atrium, delaying the signal to allow atrial contraction before ventricles.
Real data: Delay of ~0.1 seconds; located near the tricuspid valve.
Bundle of His (AV Bundle): A short pathway from the AV node, splitting into left and right branches along the interventricular septum.
Real data: Conduction speed ~1–4 m/s; length ~1–2 cm.
Bundle Branches: Right and left branches carry impulses down the septum to the ventricles.
Real data: Left branch is thicker; total conduction time from AV node to ventricles ~0.15 seconds.
Purkinje Fibers: Fine fibers spreading from bundle branches into ventricular muscle walls, triggering rapid contraction.
Real data: Fastest conduction at ~2–4 m/s; enable near-simultaneous ventricular squeeze, ejecting ~70 mL of blood per beat (stroke volume in adults).
How It Works
The SA node generates an electrical signal, spreading through atria to contract them (P wave on ECG).
Signal reaches AV node, pauses briefly, then travels via Bundle of His and branches to Purkinje fibers.
Ventricles contract from apex upward (QRS complex on ECG), followed by relaxation (T wave).
Full cycle: ~0.8 seconds at rest, maintaining cardiac output of ~5 liters/minute.