Question

What are the parts of conducting system of heart? (Class 11)

Answer 1

Answer:

The main components of the cardiac conduction system are the SA node, AV node, bundle of His, bundle branches, and Purkinje fibers. The SA node (anatomical pacemaker) starts the sequence by causing the atrial muscles to contract.

Answer 2

Conduction System of Heart: A specialized cardiac musculature called nodal tissue is distributed in heart. Conduction system of heart consists of following components:

(i) Sino–atrial node (SAN): It is located in right atrial wall just beneath opening of superior vena cava.

(ii) Atrio–ventricular node (AVN): It is located in lower left corner of right atrium close to atrio–ventricular septum.

(iii) Bundle of HIS (Atrio–Ventricular bundle):

 It continues from AVN which passes through atrio–ventricular septum, enters inter-ventricular septum and immediately divides into a right and a left bundle.

 It is the only electrical connection between atria and ventricles (elsewhere fibrous sheets of connective tissue act as electrical insulation between atria and ventricles).

(iv) Purkinje fibres: The branches of AV bundle give rise to minute fibres throughout the ventricular musculature of the respective sides and are called Purkinje fibres.

Note:  

 The nodal musculature has ability to generate action potentials without any external stimuli i.e., it is auto-excitable.

 However, the number of action potentials that could be generated in a minute vary at different parts of nodal system.

 The SAN generates maximum number of action potentials (70–75 per minute) and is responsible for initiating and maintaining the rhythmic contractile activity of heart. Therefore it is called pacemaker.

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