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Sedatives
Compounds tending to calm, and reduce nervousness or excitement and foster sleep
Sedentary Situation
Not requiring physical activity, e.g. working at a desk, sitting in a meeting or in a theater, watching television.
Septoplasty
Surgery on the nasal septum (dividing the nasal passage)
Serotonin
Neurotransmitter in the brain that modulates mood, appetite, sexual activity, aggression, body temperature and sleep
Shiftwork
Working hours outside of the conventional daytime hours of 9:00 a.m. to 5:00 p.m.
Sleep
A state marked by lessened consciousness, lessened movement of the skeletal muscles, and slowed-down metabolism
Sleep Apnea
Cessation of breathing for 10 or more seconds during sleep
Sleep architecture
NREM/REM stage and cycle infrastructure of sleep understood from the vantage point of the quantitative relationship of these components to each other
Sleep cycle
Synonymous with NREM-REM cycle
Sleep Debt
Result of recurrent sleep deprivation which occurs over time when an individual does not experience a sufficient amount of the restorative daily sleep that is required to maintain a sense of feeling rested and refreshed. .
Sleep Deprivation
Acute or chronic lack of sufficient sleep.
Sleep Disorders
Broad range of illnesses arising from many causes, including, dysfunctional sleep mechanisms, abnormalities in physiological functions during sleep, abnormalities of the biological clock, and sleep disturbances that are induced by factors extrinsic to the sleep process
Sleep efficiency (SE)
Proportion of sleep in the period potentially filled by sleep--ratio of total sleep time to time in bed
Sleep Episode
Interval of sleep that may be voluntary or involuntary
Sleep Extension
Extending sleep time by increasing the time in bed
Sleep Fragmentation
Brief arousals occurring throughout the night, reducing the total amount of time spent in the deeper levels of sleep.
Sleep hygiene
Conditions and practices that promote continuous and effective sleep, including regularity of bedtime and arise time; conforming time spent in bed to the time necessary for sustained and individually adequate sleep (i.e., the total sleep time sufficient to avoid sleepiness when awake); restriction of alcohol and caffeine beverages in the period prior to bedtime; employment of exercise, nutrition, and environmental factors so that they enhance, not disturb, restful sleep
Sleep Hyperhydrosis
Excessive sweating during sleep.
Sleep Inertia
Feelings of grogginess and/or sleepiness that persist longer than 10 to 20 minutes after waking up
Sleep interruption
Breaks in the sleep architecture resulting in arousal and wakefulness
Sleep latency
Time period measured from "lights out," or bedtime, to the beginning of sleep
Sleep log (-diary)
Daily, written record of an individual's sleep-wake pattern containing such information as time of retiring and arising, time in bed, estimated total sleep period, number and duration of sleep interruptions, quality of sleep, daytime naps, use of medications or caffeine beverages, nature of waking activities, and other data
Sleep Mentation
Thoughts, feelings, images, perceptions, hallucinations, and active dreams taking place during sleep
Sleep onset
Transition from wake to sleep, normally into NREM stage 1 (but in certain conditions, such as infancy and narcolepsy, into stage REMS)
Sleep Onset Imagery
Images and experiences during the moments following the transition from wake to sleep
Sleep paralysis
Waking and not being able to move for a short period of time, usually occurs out of REM (dream) sleep.
Sleep pattern (24 hour sleep-wake pattern)
Individual's clock hour schedule of bedtimes and rise times as well as nap behavior: may also include time and duration of sleep interruptions
Sleep Related Accidents
Accidents caused by individuals who were sleep deprived and who, as a result, had impaired judgment
Sleep Restriction
Limitation of the number of hours in bed
Sleep spindle
Episodically appearing, spindle-shaped aggregate of 12-14 Hz waves with a duration of 0.5-1.5 seconds, one of the identifying EEG phenomena of NREM stage 2 sleep
Sleep stage 1
A stage of NREM sleep occurring after wake. Its criteria consist of a low-voltage EEG with slowing to theta frequencies, alpha activity less than 50%, EEG vertex spikes, and slow rolling eye movements; no sleep spindles, K-complexes, or REMS. Stage 1 normally assumes 4-5% of total sleep.
Sleep stage 2
A stage of NREM sleep characterized by sleep spindles and K complexes against a relatively low-voltage, mixed-frequency EEG background; high-voltage delta waves may comprise up to 20% of stage 2 epochs; usually accounts for 45-55% of total sleep time.
Sleep stage 3
A stage of NREM sleep defined by at least 20 and not more than 50% of the period (30 second epoch) consisting of EEG waves less than 2 Hz and more than 75 uV (high -amplitude delta waves); a "delta" sleep stage; with stage 4, it constitutes "deep "NREM sleep; appears usually only in the first third of the sleep period; usually comprises 4-6% of total sleep time.
Sleep stage 4
All statements concerning NREM stage 3 apply to stage 4 except that high-voltage, slow EEG waves, cover 50% or more of the record; NREM stage 4 usually takes up 12-15% of total sleep time. Somnambulism, sleep terror, and sleep-related enuresis episodes generally start in stage 4 or during arousals from this stage
Sleep Stage Demarcation
Significant polysomnographic characteristics that distinguish the boundaries of the sleep stages.
Sleep stage NREM
Major sleep state apart from REMS; comprises sleep stages 1-4
Sleep stage REM
The stage of sleep found in all mammal studies, including man, in which brain activity is extensive, brain metabolism is increased, and vivid hallucinatory imagery, or dreaming occurs (in humans). Also called "paradoxical sleep" because, in the face of this intense excitation of the CNS and presence of spontaneous rapid eye movements, resting muscle activity is suppressed. The EEG is a low-voltage, fast-frequency, non alpha record. Stage REMS is usually 20-25% of total sleep time.
Sleep structure
Similar to sleep architecture. Sleep structure, in addition to encompassing sleep stage and cycle relationships, assesses the within-stage qualities of the EEG and other physiological attributes.
Sleep talking
Talking in sleep takes place during stage REMS, representing a motor breakthrough of dream speech, or in the course of transitory arousals from NREMS and other stages. Full consciousness is not achieved and no memory of the event remains.
Sleepiness (somnolence, drowsiness)
Difficulty in maintaining the wakeful state so that the individual falls asleep if not actively kept aroused; not simply a feeling of physical tiredness or listlessness
Sleeping Pills
Compounds that have a sedative effect, used to produce sleepiness
Sleep-maintenance DIMS or insomnia
Disturbance in maintaining sleep once achieved; persistently interrupted sleep without difficulty falling asleep
Sleep-onset REM period
Atypical beginning of sleep by entrance directly into stage REM
Sleep-wake shift (-change, -reversal)
Sleep wholly or partially moved to a time of customary waking activity, and the latter is moved to the habitual sleep period; common in jet lag and shift work.
Sleep-Wake Transition Disorder
Disorder occuring during the transition from wakefulness to sleep or from one sleep stage to another; a form of parasomnia
Sleep-wake, 24 hour cycle
The clock hour relationships of the major sleep and wake phases in the 24 hour cycle: similar to sleep pattern.
Sleepwalker or Sleepwalking
Individual subject to somnambulism (one who walks while sleeping). Sleepwalking typically occurs in the first third of the night during deep NREM sleep (stages 3 and 4).
Slow wave sleep (SWS)
Sleep stages 3 and 4
SmartPAP (Smart CPAP)
(Smart [Continuous] Positive Airway Pressure) Medical device used in the treatment of obstructive sleep apnea providing preset levels of continuous airflow, and automatically adjusting to keep the breathing passages open by sensing changes in airway integrity. The air flows from the device through a tube that connects to a nose or face mask.
Snoring
Noise produced primarily with inspiratory respiration during sleep owing to vibration of the soft palate and the pillars of the oropharyngeal inlet. Many snorers have incomplete obstruction of the upper airway, and may develop obstructive sleep apnea.
Soft Palate
Membranous and muscular fold suspended from the posterior margin of the hard palate and partially separating the oral cavity from the pharynx
Somatic Complaints
Awareness of pain or problems in the body
Somnambulism
Walking while asleep
Somnifacient
Inducing sleep; hypnotic, as in a drug
Somnolence
Prolonged drowsiness or sleepiness.
Somnoplasty
Commercial name for radiofrequency treatment of certain sleep disorders
Soporific
Causing or tending to cause sleep
Spindle REMS
Condition in which sleep spindles persist atypically in REMS; seen in chronic DIMS conditions
Stanford Sleepiness Scale (SSS)
7-point rating scale consisting of seven numbered statements describing subjective levels of sleepiness/alertness
Subjective Sleepiness
Feelings of sleepiness
Substance Abuse
Excessive use of alcohol or drug; substances can cause sleep disturbances
Subwakefulness syndrome
Syndrome defined as a defect in the CNS support system for waking. The few individuals reported with subwakefulness syndrome have daytime drowsiness and daytime sleep episodes that are always composed of NREMS stages 1 or 2. The naps occur repetitively
Sudden Infant Death Syndrome (SIDS)
Sudden and unexpected death of an apparently healthy infant, whose death remains unexplained after the performance of an adequate postmortem investigation. Death usually occurs during sleep. SIDS is a classification that is used to describe a deceased infant. It is not a disease, nor can it be a diagnosis for a living baby.
Synchronization
Chronobiological term used to indicate that two or more rhythms recur with the same phase relationship. In an EEG tracing, the term is used to indicate an increased amplitude with an occasional decreased frequency of the dominant activities.
Synchrony
Scheduling sleep to synchronize with the biological clock
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