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Q11:
What is the significance of atrio-ventricular node and atrio-ventricular bundle in the functioning of heart?
Solution :
1. Physiological Role of the Atrio-Ventricular Node (AVN)
The Atrio-Ventricular Node ($AVN$) is a specialized mass of cardiac muscle fibers located in the lower-left corner of the right atrium, in close proximity to the atrioventricular septum. Its significance is defined by two primary functions:
- Impulse Delay: Upon receiving the wave of contraction from the Sino-Atrial Node ($SAN$), the $AVN$ introduces a delay of approximately $0.1$ seconds [Per the physiology of the cardiac conduction system]. This delay is critical as it allows the atria to complete their systole (contraction) and fully empty their blood volume into the ventricles before the ventricles begin to contract.
- Secondary Pacemaker: The $AVN$ possesses the inherent capability to generate rhythmic electrical impulses, albeit at a lower frequency than the $SAN$ ($40-60$ beats per minute). It acts as a fail-safe mechanism, ensuring the heart maintains rhythmicity in the event of $SAN$ malfunction.
2. Physiological Role of the Atrio-Ventricular Bundle (Bundle of His)
The Atrio-Ventricular Bundle ($AV$ bundle) is a continuation of the $AVN$ that penetrates the fibrous skeleton of the heart to enter the interventricular septum. Its significance includes:
- Unidirectional Signal Conduction: The $AV$ bundle serves as the sole electrical bridge between the atrial myocardium and the ventricular myocardium, as the fibrous skeleton of the heart acts as an electrical insulator [Per the anatomical structure of the cardiac fibrous skeleton].
- Rapid Signal Distribution: It facilitates the rapid transmission of the electrical impulse from the $AVN$ to the apex of the heart through the right and left bundle branches. This ensures that the ventricular contraction begins from the apex and propagates upwards toward the base (the location of the semilunar valves), which is necessary for efficient blood ejection into the pulmonary artery and aorta.
3. Integrated Conduction Pathway Diagram
4. Comparative Summary of Cardiac Conduction Components
| Component | Primary Function | Significance |
|---|---|---|
| AV Node | Delay conduction | Prevents simultaneous atrial/ventricular contraction; allows ventricular filling. |
| AV Bundle | Conduct excitation | Links atria to ventricles; initiates synchronized ventricular systole. |
Final Solution: The Atrio-Ventricular node is essential for introducing a critical delay in impulse transmission, ensuring complete ventricular filling, while the Atrio-Ventricular bundle acts as the exclusive pathway for transmitting impulses from the atria to the ventricles, coordinating the synchronized contraction of the ventricular myocardium.
More Questions from Class 11 Biology Body Fluids and Circulation EXERCISES
- Q1: Name the components of the formed elements in the blood and mention one major function of each of them.
- Q2: What is the importance of plasma proteins?
- Q3: Match Column I with Column II : Column I Column II (a) Eosinophils (i) Coagulation (b) RBC (ii) Universal Recipient (c) AB Group (iii) Resist Infections (d) Platelets (iv) Contraction of Heart (e) Systole (v) Gas transport
- Q4: Why do we consider blood as a connective tissue?
- Q5: What is the difference between lymph and blood?
- Q6: What is meant by double circulation? What is its significance?
- Q7(a): Write the differences between : (a) Blood and Lymph
- Q7(b): Write the differences between : (b) Open and Closed system of circulation
- Q7(c): Write the differences between : (c) Systole and Diastole
- Q7(d): Write the differences between : (d) P-wave and T-wave
- Q8: Describe the evolutionary change in the pattern of heart among the vertebrates.
- Q9: Why do we call our heart myogenic?
- Q10: Sino-atrial node is called the pacemaker of our heart. Why?
- Q12: Define a cardiac cycle and the cardiac output.
- Q13: Explain heart sounds.
- Q14: Draw a standard ECG and explain the different segments in it.
CBSE Solutions for Class 11 Biology Body Fluids and Circulation
Chapters in CBSE - Class 11 Biology
- The Living World
- Biological Classification
- Plant Kingdom
- Animal Kingdom
- Morphology of Flowering Plants
- Anatomy of Flowering Plants
- Structural Organisation in Animals
- Cell – The Unit of Life
- Biomolecules
- Cell Cycle and Division
- Transport in Plants
- Mineral Nutrition
- Photosynthesis
- Respiration in Plants
- Plant Growth and Development
- Digestion and Absorption
- Breathing and Exchange of Gases
- Excretory Products and Elimination
- Locomotion and Movement
- Neural Control and Coordination
- Chemical Coordination and Integration
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