Final answer:
Lead I in an ECG records the electrical impulses between the right and left arm electrodes, which provide information on the heart's electrical activity.
Step-by-step explanation:
In Lead I of an electrocardiogram (ECG), the electrical impulses that are recorded represent the voltage difference between the right arm (RA) and the left arm (LA) electrodes. This lead measures a specific vector component of the heart's electrical activity during the process of depolarization and repolarization. Recognizing the patterns in these impulses is crucial for diagnosing various cardiac conditions and understanding heart muscle function. The ECG is an essential clinical diagnostic tool that provides information about the electrical activity of the heart by observing waves such as the P wave, QRS complex, and T wave which are each indicative of different phases of the heart's rhythmic cycle.