Final answer:
An ECG measures the electrical activity of the heart, specifically by recording the depolarization and repolarization of the atria and ventricles. Positive deflections on an ECG indicate depolarization, and the correct answer to the question is option C.
Step-by-step explanation:
An electrocardiogram (ECG) measures the electrical activity of the heart. The ECG reflects the heart's electrical impulses through voltages detected by electrodes placed on the skin. Positive deflections in an ECG represent depolarization when the heart muscle cells are electrically activated to contract, and negative deflections often indicate segments of the repolarization process when the cells are returning to their resting state after the contraction. The ECG consists of various waves and intervals, with the most prominent features being the P wave, QRS complex, and T wave. The P wave indicates atrial depolarization, the QRS complex corresponds to ventricular depolarization, and the T wave signifies ventricular repolarization. The lead II potential is commonly used to graph these activities since it provides a clear view of the electrical movements between the right arm and left leg electrodes. It is crucial for diagnosing cardiac conditions and understanding heart function.
The correct answer to the question is option C) Measures electrical activity of the heart; Positive deflections represent depolarization.