Purkinje Fibres
புர்கின்ஜே இழைகள்
The heart does not contract as a single block of muscle by accident. It relies on the Purkinje fibres to transform a slow electrical signal into a lightning-fast, synchronized ventricular contraction. If these fibres fail, the heart loses its rhythm and its life-sustaining efficiency.
The idea
Purkinje fibres are specialized conducting fibres that originate from the right and left bundle branches. They spread extensively throughout the ventricular myocardium. Their primary function is the rapid conduction of action potentials across the entire ventricular musculature. This ensures that both ventricles contract simultaneously, maximizing the ejection of blood.
Why it matters
To ensure that the entire ventricular muscle contracts almost simultaneously for efficient blood pumping.
NEET lens
NEET focuses on the sequence of the conduction system: SA node → AV node → Bundle of His → Bundle branches → Purkinje fibres. Do not confuse the origin of these fibres with the AV bundle. Remember: Purkinje fibres are the final, fastest pathway for ventricular excitation.
Clinical significance
Damage to the Purkinje system leads to Bundle Branch Blocks or ventricular arrhythmias. When conduction is delayed or blocked, the ventricles fail to contract in unison, drastically reducing cardiac output. This condition is a primary cause of heart failure and syncope.
Introduction
Purkinje fibres are specialized cardiac muscle fibres in the inner walls (subendocardium) of the ventricles that rapidly conduct electrical impulses from the Bundle of His to the ventricular myocardium, ensuring coordinated ventricular contraction.
Core concept
Location: subendocardial layer of ventricular walls, spread from Bundle of His branches. Structure: large diameter fibres → very fast conduction velocity (~4 m/sec, fastest in heart). Function: rapidly spread impulse from apex upward → ventricles contract from bottom up → blood efficiently ejected toward semilunar valves at top. Conduction pathway: AV node → Bundle of His → Left + Right bundle branches → Purkinje fibres → ventricular myocardium. The coordinated bottom-to-top ventricular contraction is due to Purkinje fibre distribution.
Go deeper
Why apex-to-base contraction? Purkinje fibres reach the apex first → apex contracts first → squeezes blood upward toward aorta/pulmonary artery (which exit at the base). If contraction started at base → blood pushed toward apex (dead end) → inefficient ejection.
From Class 10
After the electrical impulse crosses the AV node, it needs to rapidly spread across the entire ventricle. Specialized conducting fibres — Purkinje fibres — do this at very high speed.