This document discusses sleep and the brain waves associated with it. It defines sleep and describes the two types: slow wave sleep and REM sleep. It explains the neuronal centers and neurotransmitters involved in inducing each type of sleep. The sleep cycle is described as the result of three systems - the arousal system, slow wave sleep center, and REM sleep center - interacting cyclically. The document also outlines the different brain waves seen in EEGs - alpha, beta, theta, and delta waves - and their characteristics and associations with different brain states.