Summary of Sleep and Biological Rhythms

3.1 Sleep

  • Sleep is a behavior with minimal movement, crucial for survival.

  • Requires a warm, quiet, and comfortable environment.

  • Represents a change in consciousness, impacting state of awareness.

3.1.1 Stages of Sleep and Wakefulness

  • Wakefulness:

    • Alpha Waves (8-13 Hz): Occur during relaxed states.

    • Beta Waves (13-30 Hz): Associated with active mental engagement.

  • Synchrony and Desynchrony:

    • Synchrony denotes clear, large wave patterns; desynchrony leads to chaotic waveforms.

Sleep Stages:

  • Stage 1:

    • Transition phase lasting ~10 minutes.

    • Characterized by theta waves (3.5-7.5 Hz), eyelid movement, and muscle twitches.

  • Stage 2:

    • Irregular EEG activity, heart rate, and breathing slow down.

    • Features sleep spindles; critical for memory consolidation.

  • Stage 3:

    • Transitional stage toward deep sleep; hosts restorative processes.

    • Associated with disorders like sleepwalking.

  • Stage 4:

    • Dominated by delta waves; essential for sleep quality assessment.

    • Deepest sleep stage lasting ~20 minutes.

  • REM Sleep:

    • High brain activity akin to wakefulness; dreams occur and significant processing of information takes place.

    • Increased oxygen consumption and unique physiological responses.

3.2 Functions of Sleep

  • REM sleep seen in warm-blooded animals; reflects evolutionary importance.

  • Sleep deprivation negatively affects cognitive abilities and recovery post-deprivation varies by sleep stage.

3.3 Physiological Mechanisms of Sleep

Chemical and Neural Control:

  • Adenosine: Builds during wakefulness, regulating sleep need.

  • Neurotransmitters (Ach, NA, 5-HT, etc.) coordinate wakefulness and sleep; certain key areas in the brain control these processes.

3.4 Sleep Disorders

  • Insomnia: Difficulty with sleep initiation and maintenance. Treatment includes psychological methods and pharmacological aids.

  • Apnea: Breathing difficulties during sleep lead to disruptions.

  • Narcolepsy: Characterized by sleep paralysis and hallucinations; associated with orexin deficits in the brain.

  • REM Sleep Behavior Disorder: Inability to inhibit movement during REM sleep, often linked to neurodegenerative conditions, particularly Parkinson's disease.

  • Other Disorders: Include sleepwalking, night terrors, and eat-related sleep disturbances.