1. Identifying the Heart's Signal: The heart operates via electrical impulses that trigger the contraction of cardiac muscle. The recording of this electrical activity over a period of time using electrodes placed on the skin is known as Electrocardiography.
2. Analyzing the Options:
• ECG (Electrocardiogram): Specifically designed to detect and amplify the tiny electrical changes on the skin that arise from the heart muscle's electrophysiologic pattern of depolarizing and repolarizing during each heartbeat.
• EMG (Electromyogram): Used to measure the electrical activity of skeletal muscles.
• EEG (Electroencephalogram): Used to record electrical activity of the brain (brain waves).
• Thermometer: A device used to measure temperature, not electrical activity.