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What does the vertical axis on an ECG reading represent?

  1. Time

  2. Amplitude

  3. Voltage

  4. Heart rate

The correct answer is: Voltage

The vertical axis on an ECG reading represents voltage, which is related to the electrical activity of the heart. Each deflection from the baseline on the vertical axis indicates the amplitude of electrical potentials generated by the depolarization and repolarization of cardiac cells as the electrical impulse travels through the heart. By measuring these voltage changes, healthcare providers can assess the heart's rhythm, detect abnormalities, and analyze the overall electrical function of the heart. Understanding that the vertical axis corresponds to voltage helps clinicians interpret the strength of the electrical signals, which is crucial for diagnosing various cardiac conditions.