kolbintro6e_lectureslides_ch13_UPLOAD

Why Do We Sleep and Dream?

• Key Topics:

  • Biological rhythms and their origins

  • Suprachiasmatic biological clock

  • Sleep stages and dreaming

  • Functions of sleep

  • Neural bases of sleep

  • Sleep disorders

  • Connection between sleep and consciousness

Origin of Biorhythms

• Biorhythm: Inherent timing mechanism controlling various biological processes.

  • Influenced by Earth's rotation around the sun and seasonal changes.

  • Animals near the poles more affected by seasonal changes than equatorial animals.

  • Plants exhibit biorhythms; e.g., leaves open/close with the sun.

• Human Biorhythms:

  • Evolution as equatorial creatures leads to circadian rhythms of daytime activity and nighttime sleep.

  • Daily Cycles in Humans: Include variations in pulse rate, blood pressure, body temperature, cell division, blood cell count, alertness, and behavioral responses.

Biological Rhythms

• Types of Biological Rhythms:

  • Circannual: Yearly cycles; e.g., migratory cycles of birds.

  • Circadian: Daily cycles; e.g., human sleep-wake cycles.

  • Ultradian: Less than a day; e.g., eating cycles.

  • Infradian: More than a day; e.g., human menstrual cycle.

Circadian Rhythms

• Endogenous Control: Behavior influenced by internal mechanisms rather than solely external cues (e.g., light).

• Function of Biological Clock: Helps predict events, regulates feeding/sleep times, metabolic activity, and gene expression across the body.

Free-Running Rhythms

• Defined as body rhythms absent of external cues; typically ranging from 25-27 hours when isolated.

• Effect of Light Conditions:

  • Animals adjust their sleep periods based on light exposure; e.g., hamsters' periods shift in constant darkness/light.

Zeitgebers

• Environmental events that reset biological rhythms, primarily light.

  • ** Entrainment:** Synchronization with environmental cues; influences daily activities.

  • Light Pollution: Disrupts circadian rhythms leading to various health issues and behavioral inconsistencies.

Jet Lag

• Fatigue and disorientation due to rapid time zone changes affecting biological clocks.

  • Adjustment Difficulty: More challenging to adjust traveling west-east than east-west.

Suprachiasmatic Biological Clock (SCN)

• Main pacemaker of circadian rhythms located above the optic chiasm.

  • Damage Effects: SCN damage leads to disorganized daily activities; metabolic activity increases during light cycles.

Neural Bases of Sleep

• Melatonin: Produced by the pineal gland and signals sleepiness.

• Reticular Activating System (RAS): Associated with sleep-wake behavior; disruption can lead to coma-like states.

Sleep Stages and Dreaming

• Measuring Sleep: Uses a polygraph to record electrical activity, including EEG, EMG, and EOG.

• Sleep Stages:

  • NREM Stages: Include shallow to deep sleep, with varying brain activity and no vivid dreaming.

  • REM Sleep: Characterized by fast brain waves, vivid dreams, and muscle atonia.

Disorders of Sleep

• Insomnia: Prolonged inability to sleep; caused by anxiety, depression, or drug dependence.

• Narcolepsy: Involuntary sleep episodes at inappropriate times.

• Sleep Apnea: Characterized by breathing interruptions during sleep.

Sleep and Memory

• Sleep is critical for memory consolidation involving distinct phases: labile, consolidation, and recall.

• Different sleep states interact with memory processes, possibly influencing how memories are stored and retrieved.