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Psychology - Sleep and Consciousness

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  • What is a circadian rhythm?

    A circadian rhythm is the 24-hour sleep-wake cycle in humans that regulates many body processes.

  • What structure controls the circadian rhythm?

    The suprachiasmatic nucleus (SCN) in the hypothalamus controls the circadian rhythm.

  • What external cue mainly influences the SCN?

    The SCN mainly responds to light as an external cue.

  • What gland does the SCN trigger to release melatonin?

    The SCN triggers the pineal gland to release melatonin.

  • What hormone is released to promote sleep?

    Melatonin is the hormone released by the pineal gland to promote sleep.

  • What happens to circadian rhythms when disrupted by jetlag or night shifts?

    Circadian rhythms can become dysregulated, causing sleep problems.

  • What are the two general phases of sleep?

    Sleep is divided into REM (Rapid Eye Movement) and NREM (Non-REM) phases.

  • How long does one sleep cycle last and how many cycles occur per night?

    Each sleep cycle lasts about 90-120 minutes, with typically 4-6 cycles per night.

  • What characterizes REM sleep?

    REM sleep features rapid eye movements, vivid dreams, increased heart rate, increased respiration, and muscle paralysis.

  • What characterizes NREM sleep?

    NREM sleep has four stages of light to deep sleep, with decreased heart rate and respiration.

  • What tool is used to visualize brainwaves during sleep?

    An EEG (electroencephalogram) measures electrical activity in the brain to visualize brainwaves.

  • What are the key EEG wave characteristics to consider?

    Frequency (cycles per second) and amplitude (height) of brainwaves indicate brain activity levels.

  • Describe the EEG waves during the awake state.

    Awake EEG shows beta waves: high frequency and low amplitude.

  • What EEG waves appear in Stage 1 sleep?

    Stage 1 sleep shows theta waves, which have lower frequency than beta waves.

  • What EEG features are seen in Stage 2 sleep?

    Stage 2 sleep has sleep spindles (high frequency bursts) and K complexes (high amplitude waves).

  • What characterizes Stages 3 and 4 sleep on EEG?

    Stages 3 & 4 show delta waves, which have the lowest frequency and highest amplitude, indicating deep sleep.

  • How does REM sleep EEG compare to awake EEG?

    REM sleep EEG resembles awake EEG with beta-like waves, despite muscle paralysis.

  • What happens to the amount of deep sleep (Stages 3 & 4) as the night progresses?

    The amount of deep sleep decreases as the night goes on.

  • What happens to REM sleep duration throughout the night?

    REM sleep duration increases as the night progresses.

  • What stage do people re-enter if they wake up during the night?

    People typically re-enter Stage 1 sleep after waking up during the night.