Figure 32.10: The Electrocardiogram (EKG) Is an Electrical Signature of Heart Action (A) To record the EKG, two electrodes are placed in contact with the skin at two different locations. The voltage difference between the electrodes is measured and recorded as a function of time. (B) A normal EKG record from a person. A series of electrical events—consisting of defined waveforms—occurs during each heartbeat. The waveforms are named P, Q, R, S, and T.