Cardiac Nodal Tissue & Conduction — NEET Biology
✅ Asked in NEET 2024Following 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
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
Match List I with List IIList I A. Tricuspid valves B. Sino-atrial node C. Mitral valves D. Semilunar valves List II I. Guards the opening between the right atrium and the right ventricle II. Guards the opening between the left atrium and the left ventricle III. Guards the opening of right and left ventricles into pulmonary artery and aorta, respectively IV. Cardiac musculature in the right upper corner of right atrium
Answer & NCERT explanation
Correct answer: A — E–C–A–D–B
Cardiac conduction pathway: SA node (pacemaker) generates impulse → AV node delays impulse → AV bundle conducts through septum → Bundle branches divide to left and right → Purkinje fibers distribute throughout ventricles. This sequence ensures coordinated contraction as per NCERT cardiac physiology.
Read more NCERT concept on the PYQ
The entire heart is made of cardiac muscles. The walls of ventricles are much thicker than that of the atria. A specialised cardiac musculature called the nodal tissue is also distributed in the heart. A patch of this tissue is present in the right upper corner of the right atrium called the sino-atrial node (SAN). Another mass of this tissue is seen in the lower left corner of the right atrium close to the atrio-ventricular septum called the atrio-ventricular node (AVN). A bundle of nodal fibres, atrio-ventricular bundle (AV bundle) continues from the AVN which passes through the atrio-ventricular septa to emerge on the top of the inter-ventricular septum and immediately divides into a right and left bundle. These branches give rise to minute fibres throughout the ventricular musculature of the respective sides and are called purkinje fibres. The nodal musculature has the ability to generate action potentials without any external stimuli, i.e., it is autoexcitable. However, the number of action potentials that could be generated in a minute vary at different parts of the nodal system. The SAN can generate the maximum number of action potentials, i.e., 70-75 min⁻¹, and is responsible for initiating and maintaining the rhythmic contractile activity of the heart. Therefore, it is called the pacemaker. Our heart normally beats 70-75 times in a minute (average 72 beats min⁻¹).
NTA tests your understanding of the nodal tissue pathway that controls heart rhythm: SAN (pacemaker) → AVN → AV bundle → bundle branches → Purkinje fibres. The key concept is that the SAN initiates heartbeats at 70-75 bpm because it generates the most action potentials, making it the pacemaker. Students often confuse which node does what—remember SAN fires fastest and starts the beat, while AVN creates a delay for atrial emptying. The Purkinje fibres ensure synchronized ventricular contraction. NEET typically asks which tissue initiates the heartbeat or about conduction velocity differences between nodes. Focus on the sequence and functional significance of each component.
What does NCERT say about entire heart made cardiac?
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