Question

Sino-atrial node is called the pacemaker of our heart. Why?

Answer 1

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❇ 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 atrioventricular septum called the atrioventricular node (AVN).

❇A bundle of nodal fibres , Atrioventricular 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 left and right bundle.

❇These branches give rise to minute fibres throughout the ventricular musculature of the respective sides and are called Purkinje fibres.

❇These fibres along with right and left bundles are known as Bundle of His.

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✔ The nodal musculature has the ability to generate action potentials without any external stimuli i.e., it's 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 the initiating and maintaining the rhythmic contractile activity of the heart.

✔ Therefore, it is called the Pacemaker.


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