Among the minor disorders are sleepwalking, sleeptalking, enuresis, bruxism (tooth grinding), and nightmares. Sleep disorders chronic disorders involving sleep primary sleep disorders are classified as dyssomnias or parasomnias. During REM sleep it is believed that there is increased metabolic activity in the brain so that during waking hours it is more receptive to new information and can assimilate it more easily. It is also theorized that REM sleep provides a period of recuperation of mental activities and preparation for wakefulness. For example, even though the function of stage 2 NREM sleep is not clear, approximately half of human sleep time is spent in this stage. The relatively high metabolic needs of mammals and birds to maintain a constant body temperature in a wide range of environmental temperatures suggests that the periodic decreases in metabolic rate and body temperature that occur in NREM sleep allow for recuperation and restitution of body tissues. Most theorists agree that sleep has value as a recuperative and adaptive function in the lives of humans. An adult usually requires 6 to 9 hours of total sleep, and requirements continue to decrease with aging. Infants usually require 16 to 20 hours of total sleep during a 24-hour period, and the amount decreases as the child matures. Sleep requirements vary greatly among individuals. This is probably because of increased autonomic activity, irregular pulse, and fluctuations in blood pressure, which are all typical of REM sleep.īenefits of Sleep. Convulsions, myocardial infarction, and cardiac arrhythmias are more likely to occur during REM sleep. In addition to the rapid eye movements that can be observed through closed eyelids, REM sleep can be recognized by complete relaxation of the lower jaw. While everyone dreams every night, many do not remember dreaming most people are aware, however, that they dream more just before rising. With each cycle, NREM sleep decreases and REM sleep increases so that by the end of the night most of the sleep is REM sleep, which is when dreams occur. Brief cycles of about 10 to 30 minutes of REM sleep recur throughout the night, alternating with various stages of NREM sleep.
#Sleeping dogs lie meaning series#
Within 90 minutes after sleep begins, an adult progresses through all four stages of NREM sleep and then proceeds into the first of a series of REM periods of sleep. NREM sleep is increased after physical activity and has a relatively high priority among humans in the recovery sleep following extended periods of wakefulness. The EEG patterns of NREM sleep suggest that this is the kind of apparently restful state that supports the recuperative functions assigned to sleep. Stages 3 and 4 consist of relatively high voltage EEG tracings with a predominance of delta wave activity (one to two hertz). Stage 2 is characterized by intermittent waves of 12 to 16 hertz, known as sleep spindles. Stage 1 is observed immediately after sleep begins or after momentary arousals and is characterized by low-voltage, mixed-frequency EEG tracing, with predominantly theta-wave activity (four to seven hertz, that is, cycles per second). On the basis of electroencephalographic (EEG) criteria, NREM sleep is subdivided into four stages. Studies concerned with the measurement of central and autonomic activities during sleep have led to its division into two types: non–rapid eye movement (NREM) sleep, also called orthodox or synchronized (S) sleep and rapid eye movement (REM) sleep (so called because of the rapid eye movements during this stage), also called paradoxical or desynchronized (D) sleep. Prior to the discovery and reporting of rapid eye movements during sleep, it was thought that sleep was a single state of passive recuperation in which the central nervous system was deactivated.