24 - NREM sleep

NREM sleep:

© SPMM Course 5. Physiology of sleep A. Measurement  Actigraphy: This is used to quantify circadian sleep-wake patterns and to detect movement disorders during sleep; it uses a motion sensor.  Polysomnography (PSG): This includes EEG, electromyogram (EMG), electrooculogram EOG. ECG, oximetry and respiratory monitor can also be added. PSG helps in the diagnosis and monitoring of sleep apnoea, narcolepsy, restless legs & REM behavioural disorder. Some of the terms used in PSG are o Sleep latency: time from ‘lights out’ to sleep onset. o REM latency: Time from sleep onset to first REM episode. Normally ~90 minutes in adults. o Non-REM latency: Time from sleep onset to first Non-REM episode. o Sleep efficiency: (Total sleep time/total time in bed) X 100. o Multiple sleep latency test: This is used to assess daytime somnolence and daytime REM onset in narcolepsy. B. Architecture The average length of sleep is approximately 7.5 hours per night. Sleep is made up of non-rapid eye movement (NREM) and rapid eye movement (REM) phases. NREM sleep: o 75% of adult sleep is NREM. Most physiological functions are markedly lower in NREM than in wakefulness (decreased muscle tone, respiration, temperature and heart rate). o NREM is classified as stages 1 to 4 with increasing amplitude and decreasing frequency of EEG activity. Stages 3 & 4 together constitute slow wave sleep (SWS). SWS dominates initial part of the sleep. o Features of non-REM sleep includes  Increased parasympathetic activity (decreased heart rate, systolic blood pressure, respiratory rate, cerebral blood flow)  Abolition of tendon reflexes  The upward ocular deviation with few or no movements. • 5% of sleep • Drowsy period. When awoken from this stage one denies being asleep. • Shows low voltage theta activity, sharp V waves. Stage 1 NREM sleep Stage 1 NREM sleep •45% of sleep •Shows the development of sleep spindles and K complexes. Stage 2 NREM sleep Stage 2 NREM sleep •12% of sleep •Shows <50% delta waves. Stage 3 NREM sleep Stage 3 NREM sleep •13% of sleep •Shows >50% delta waves. •Physiological functions are at the lowest Stage 4 NREM sleep Stage 4 NREM sleep DREAMS Dreaming occurs at all stages of sleep, but the content varies. In non-REM sleep the dreams are thought-like as though the person is solving a problem. In REM sleep the dreams may be illogical and bizarre.