Chapter 14 Sleep, dreaming and circadian rhythms

Chapter 14 Sleep, dreaming and circadian rhythms - 1...

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1 Chapter 14: Sleep, Dreaming and Circadian Rhythms Topic Covered Physiological and Behavioural Events of Sleep REM sleep and dreaming Why do we sleep? Circadian Sleep Cycles Effects of Sleep Deprivation Areas of the brain involved in sleep Circadian Clock – Neural and Molecular Mechanisms Drugs that affect sleep Sleep Disorders The effects of long term sleep reduction How much sleep do we need? The vast amount of time spent sleeping suggests that sleep has a significant biological function. What is the function? What brain mechanisms control sleep? How does sleep deprivation impact functioning? What happens to you when you don’t get enough sleep? Or are we getting enough sleep? http://www.telegraph.co.uk/news/uknews/3206621/Sleep-deprivation-is-a-myth-expert- claims.html Figure 14.2 (EEG for alert wakefulness, just before sleep, and stage 1, 2, 3 and 4) 14.1 3 Physiological Measures of Sleep Electroencephalogram (EEG) - “Brain waves” - Pick up electrical signals on the head Electrooculogram (EOG) - Eye movements seen during rapid eye movement (REM) sleep Electromyogram (EMG) - Loss of activity in neck muscles during some sleep stages - Loss of muscle tone during certain sleep stages
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2 Stages of sleep EEG 1. Alpha waves - Bursts of 8- to 12-Hz EEG waves - Eyes closed, preparing to sleep 2. Stage 1 - Similar to awake EEG, but slower - Low-voltage, high-frequency 3. Stage 2 - Higher amplitude, lower frequency - 2 punctuated by K complex (single large –ve wave & single large +ve wave) and sleep spindles (1-2sec, 12-14 Hz) (very high frequency suddenly) 4. Stage 3 - Occasional delta waves 5. Stage 4 - Predominantly delta waves Stages of Sleep EEG Progress to stage 4 sleep then retreat to stage 1 Emergent stage 1 different from initial stage 1 - REMs - Loss of body core muscle tone Progress through sleep stages in 90-minute cycle More time spent in emergent stage 1 as night progresses Emergent stage 1 sleep = REM sleep - Non-REM (NREM) sleep = all other stages - Loss of core muscle tone - However, cerebral activity increases in most brain areas to waking levels Stage 2 + 3 + 4 = slow-wave sleep (SWS) Figure 14.3 14.3 Why do we sleep? Recuperation theories - Sleep is needed to restore homeostasis - Wakefulness causes a deviation from homeostasis Circadian theories - Sleep is the result of an internal timing mechanism (SCN) - Sleep evolved to protect us from the dangers of the night (predators)
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3 14.4 Comparative Analysis of Sleep All mammals and birds sleep – must have an important function - Not a special higher-order human function Not necessarily needed in large quantities No clear relationship between species’ sleep time and activity level Thought question: what can the article teach us? 14.5
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This note was uploaded on 04/27/2010 for the course PSYCHOLOGY SPC 211 taught by Professor Ms.chitra during the Spring '10 term at Sunway University College.

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Chapter 14 Sleep, dreaming and circadian rhythms - 1...

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