What is the central terminal in an ECG?

The central terminal in an ECG refers to a constructed reference point that represents the average electrical potential from the limb electrodes. This averaging process provides a stable baseline for the ECG readings, allowing for more consistent and accurate interpretation of the heart's electrical activity as recorded by the leads.

In an ECG setup, the central terminal is derived from the limb leads, specifically a combination of the potentials from the right arm, left arm, and left leg electrodes. By averaging these potentials, the central terminal helps to minimize noise and improve the clarity of the ECG waveforms, making it easier to identify and analyze the various cardiac events represented on the ECG.

This concept is crucial for understanding how the ECG works, as it allows healthcare professionals to focus on the deviations from this average potential, which can indicate various cardiac conditions. The other options provided do not accurately describe the function or definition of the central terminal in the context of an ECG.