Lecture 15 - Sleep, Dreaming, and Circadian Rhythms.docx - Jessica Weissman BCS 110 Lecture 15 – Sleep Dreaming and Circadian Rhythms Sleep-Wake Cycle

Lecture 15 - Sleep, Dreaming, and Circadian Rhythms.docx -...

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Jessica Weissman BCS 110 Lecture 15 – Sleep, Dreaming, and Circadian Rhythms Sleep-Wake Cycle People typically sleep about 8 hours per day, and spend 16 hours awake. Most people sleep over 175,000 hours in their lifetime. The vast amount of time spent sleeping suggests that sleep has a significant biological function. Recuperation As we are awake for 16 hours of the day, our physical and mental exertion leaves our ionic concentrations out of balance, muscles have lost energy Adaptation Since night time is approaching, we are a danger to ourselves and prey for others since we are not suited for lifetime activity, adapting to rest somewhere where we are safe from nighttime activities Three Physiological Measures of Sleep Electroencephalogram (EEG) reveals gross electrical activity of the brain “brainwaves” Performed by sticking an electrode on the individual’s head Electrooculogram (EOG) records eye movements seen during rapid eye movement (REM) sleep Electromyogram (EMG) detects loss of activity in neck muscles during some sleep stages Four Stages of Sleep EEG Awake low-voltage, high-frequency (fast) waves Pre-sleep intermittent alpha waves, bursts of low-frequency (8-12 Hz) waves Sleep voltage increases and frequency decreases (slows) with progression through stages 1-4 Stage 1: theta waves (characteristic of light sleep) Stage 2: spindles and K complexes signals the brain uses to keep you asleep Still receiving lots of sensory input, the thalamus tells you the sensory information around you is not important First two stages of sleep are defined as light sleep Stage 3: occasional delta waves (large and slow, 1-2 Hz) Stage 4: predominantly delta waves
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Course of Sleep and REM Sleep A sleeper progresses from stage 1 to stage 4 sleep and then back through stages 3, 2, to (emergent) stage 1, then repeats the cycle. Emergent stage 1 differs from initial stage 1 (and all other stages): Rapid eye movement (REM) sleep – dreams Loss of body core muscle tone (cerebral activity increases to awake levels) Sleepers progress through sleep stages in 90-minute cycles, where the durations of emergent stage 1 periods lengthen and stages 3-4 shorten as the night progresses.
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  • Spring '08
  • Holtzman
  •  Recuperation

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