Final answer:
Positive impulses on an ECG tracing are represented by upward deflections. This includes the P wave for atrial depolarization and the QRS complex for ventricular depolarization. The T wave, representing ventricular repolarization, also manifests as an upward deflection when it reflects positive repolarization.
Step-by-step explanation:
When analyzing an ECG tracing, positive impulses are seen as upward deflections. The ECG tracing typically shows several key components including the P wave, QRS complex, and T wave. The P wave corresponds to atrial depolarization, the QRS complex corresponds to ventricular depolarization, and the T wave represents ventricular repolarization. The ST segment and J point are other elements of the ECG but do not represent positive electrical impulses directly.
Depolarization begins at the atria, with the P wave indicating the atria contracting shortly thereafter. This continues with the ventricles, as indicated by the QRS complex, which, due to the ventricles' larger size, is much larger and stronger. Ventricular contraction begins at the peak of the R wave. Atrial repolarization happens during the QRS complex, but it is not visible on the ECG as it is obscured by the larger signals from the ventricles.