The SA is the heart's normal pacemaker because A) It has the fastest rate of autorhythmicity. B) It has both sympathetic and parasympathetic innervation. C) It lies in the right atrium. D) Activation of K⁺ channels occurs more rapidly in this region than elsewhere in the heart. E) None of these.

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Quizplus · Accepted Answer

The SA node has the fastest rate of autorhythmicity, meaning it can spontaneously generate action potentials at a faster rate than any other region of the heart. This is why it is considered the heart's primary pacemaker.

The SA Is the Heart's Normal Pacemaker Because