This chapter explores the electrophysiology of the motor system with a focus on transcranial motor evoked potentials (TCMEPs), direct waves (D-waves), and indirect waves (I-waves) in the context of intraoperative neuromonitoring. It details the corticospinal tract’s anatomy and the physiological mechanisms governing motor responses. The chapter highlights the impact of anesthesia on synaptic transmission, particularly its suppressive effects on I-waves and alpha motor neuron excitability. It explains how multipulse transcranial stimulation overcomes these limitations by generating successive D-waves, facilitating MEP monitoring even under deep anesthesia. By integrating anatomical, physiological, and technical insights, this chapter provides a foundation for optimizing motor system monitoring in intraoperative settings.