Final answer:
The horizontal flat line on an ECG strip that separates the waves is known as the baseline, and it is essential for accurately measuring segments and intervals important in assessing heart function.
Step-by-step explanation:
The horizontal flat line that separates the various waves on the ECG strip represents the baseline. In an ECG tracing, segments are defined as the regions between two waves, whereas intervals include one segment plus one or more waves. The baseline serves as the reference line or starting point from where the amplitude of the waves is measured. The amplitude is the characteristic height of a wave, above or below the equilibrium or baseline position. When interpreting an ECG, it is important to identify the baseline correctly to accurately measure the segments and intervals, such as the PR segment and interval, which have clinical significance in assessing the heart's electrical activity and function.