Sleep and Waking

Learning Objectives

  • L01: Differentiate between types of biological rhythms.

  • L02: Describe the brain structures and neurochemicals managing waking and sleep.

  • L03: Analyze theories explaining the functions of sleep.

  • L04: Describe the features, causes, and treatments of major sleep-wake disorders.

Key Concepts

  • Biorhythms: Regular patterns of physiological activity. Includes:

    • Circadian Rhythms: 24-hour cycles related to light/dark variations.

    • Ultradian Rhythms: Intervals shorter than 24 hours, such as 90-120 minutes sleep cycles.

  • Zeitgebers: External cues that regulate biological rhythms (e.g., light, temperature, meal times).

  • Chronotypes: Individual differences in sleep patterns (e.g., larks vs. owls).

Circadian Rhythms

  • Controlled by the suprachiasmatic nucleus (SCN) in the hypothalamus.

  • Light is the primary zeitgeber; blind individuals often experience free-running cycles.

  • Changes in sleep patterns can occur due to factors like shift work and jet lag:

    • Shift Work: Workers can experience disruptions in their internal biological clocks, leading to health issues.

    • Jet Lag: Results from traveling across time zones; effects include fatigue and disrupted sleep.

Reasons for Sleep

  • Four major theories herald potential functions of sleep:

    • Safety: Reduces activity during high-risk periods (predation risks).

    • Restoration: Rejuvenates and maintains body functions (e.g., immune function).

    • Memory Consolidation: Helps stabilize and integrate new information from waking hours.

    • Emotional Regulation: Sleep can alter emotional reactions and support mental health.

Sleep Stages

  • Non-Rapid Eye Movement (NREM) Sleep: Comprises three stages:

    • Stage 1: Light sleep (theta waves begin).

    • Stage 2: Deeper sleep, includes sleep spindles and K-complexes.

    • Stage 3: Deep sleep (delta waves).

  • REM Sleep: Characterized by vivid dreaming, muscle paralysis, and high brain activity resembling wakefulness.

Sleep Disorders

  • Circadian Disorders: E.g., Delayed Sleep-Wake Phase Disorder (late sleeping), Advanced Sleep-Wake Phase Disorder (early sleeping).

  • Insomnia: Difficulty initiating or maintaining sleep. Can be caused by stress or environmental factors.

  • Narcolepsy: Characterized by sudden sleep attacks and REM sleep phenomena intruding into wakefulness.

  • Sleep Apnea: Breathing disruptions during sleep; can be central or obstructive.

  • Restless Legs Syndrome (RLS): Unpleasant sensation in legs, leading to an urge to move them.

Treatments for Sleep Disorders

  • Cognitive Behavioral Therapy for Insomnia (CBT-I): First-line treatment for chronic insomnia.

  • Melatonin: Used for circadian disorder treatment.

  • Stimulants: Can be used for narcolepsy management.

  • CPAP machines: Preferred for treating obstructive sleep apnea.

Neurochemical Regulation

  • Key neurochemicals in sleep and wakefulness include:

    • Melatonin: Signals sleep onset.

    • Cortisol: Higher in the morning, involved in stress responses.

    • Adenosine: Accumulates during wakefulness, promotes sleep.

    • Acetylcholine: Linked with arousal and REM sleep.

    • Histamine, Norepinephrine, Serotonin: Play roles in wakefulness regulation.

Summary

Understanding sleep and its many functions is crucial for managing health and behavior. This includes recognizing the types of sleep disorders and their impacts on daily life, as well as treatments available. Studying sleep patterns contributes to a greater understanding of psychological well-being and cognitive functioning.