What is the outcome when impulses travel toward a negative electrode?

• A. Upward deflection
• B. Flat tracing
• C. Downward deflection
• D. No deflection

Answer: (C)

When impulses travel toward a negative electrode, the result is a downward deflection on the electrocardiogram (ECG) tracing. This occurs because the ECG machine measures the difference in electrical potential between electrodes. If the electrical wave is moving towards a negative electrode, it indicates that the positive side of the wave is positioned farther away from the negative electrode. Therefore, the resulting graphical representation on the ECG reflects this movement as a downward deflection.

In cardiac electrical activity, the positive electrodes register positive deflection when they detect depolarization occurring towards them. Conversely, if the depolarizing wavefront moves towards a negative electrode, the result is a decrease in the electrical potential detected at that electrode, which is visually depicted as a downward mark on the ECG graph. This relationship between the direction of impulse movement and the resultant deflection is fundamental to interpreting heart rhythms and identifying abnormal electrical activity in cardiac testing.