This beautifully illustrated chart defines sleep and the sleep-wake cycle, explains why the body needs sleep, and describes the role of the suprachiasmatic nucleus (SCN) of the brain in sleep and wake regulation. The chart graphs and describes the five phases of sleep and covers common sleep disorders such as insomnia, obstructive sleep apnea, restless legs syndrome (RLS), and narcolepsy. Tips for a good night's sleep are also included. Size: 20" W x 26" L