All the components of the nodal tissue are autoexcitable. Why does the SA node act as the normal pacemakar?

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SA node has the lowest rate of depolarisation.

SA node is the only component to generate the threshold potential.

Only SA node can convey the action potential to the other components.

SA node has the highest rate of depolarisation.

answer is D.

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Detailed Solution

All the components of the nodal tissue are autoexcitable (have the ability to generate action potentials without any external stimuli). 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.,70-75min-1, and is responsible for initiating and maintaining the rhythmic contractile activity of the heart. Therefore, it is called the pacemaker.

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