Biology · Body Fluids and Circulation · NEET
SA node (SAN) generates the impulse, then it passes to the AV node (AVN), then to the AV bundle (bundle of His), which splits into the right and left bundle branches, and finally the Purkinje fibres carry it through the whole ventricular muscle. In NEET 2024 the letter order was E-C-A-D-B. Learn it forward and never break the chain.
The AVN holds the signal for roughly 0.1 second so that atrial contraction (atrial systole) finishes first. This lets the atria empty their blood completely into the ventricles before the ventricles contract. NEET 2019 tested exactly this: the delay 'allows the atria to empty completely'.
Yes. NCERT calls it the 'atrio-ventricular bundle (AV bundle)', and it is the same structure as the bundle of His. It continues from the AVN, passes through the atrio-ventricular septum, and then divides into the right and left bundle branches. Do not treat AV bundle and bundle of His as two different steps.
After. The order is bundle branches first, then Purkinje fibres. The bundle branches run down the sides of the ventricles, and the Purkinje fibres are the fine terminal branches that spread the impulse into the ventricular muscle to cause ventricular systole. Reversing these two is the most common mistake.
It begins at the SA node in the upper right corner of the right atrium. The SAN is the pacemaker because it generates the maximum action potentials (about 70-75 per minute) and depolarises fastest, so it sets the rhythm for the whole heart.
Following are the stages of pathway for conduction of an action potential through the heart: A. AV bundle, B. Purkinje fibres, C. AV node, D. Bundle branches, E. SA node. Choose the correct sequence of pathway.
A specialised nodal tissue embedded in the lower corner of the right atrium, close to the atrio-ventricular septum, delays the spreading of impulses to the heart apex for about 0.1 sec. The delay allows:
Try the real previous-year questions from this chapter — each with the answer and a full solution.
SA node to AV node to AV bundle (bundle of His) to right and left bundle branches to Purkinje fibres, which then spread the impulse across the ventricle walls.
Because it generates the most action potentials, about 70-75 per minute, and depolarises fastest, so it sets the heartbeat rhythm for the whole heart.
About 0.1 second. This short pause lets the atria finish contracting and empty fully into the ventricles before the ventricles contract.
No. NCERT uses 'AV bundle', which is the same structure as the bundle of His. Count it as one step in the pathway.
They are the fine terminal fibres that carry the impulse into the ventricular muscle, causing the ventricles to contract (ventricular systole).
