JL

Psych 4.1 Consciousness and Sleep

Understanding Consciousness, Biological Rhythms, and Sleep

Learning Objectives

By the end of this study, you should be able to:

  • Understand the concept of consciousness.

  • Explain the role of circadian rhythms in regulating the sleep-wake cycle and how they can be disrupted.

  • Discuss the concept and implications of sleep debt.

Consciousness

  • Definition: Consciousness describes our awareness of internal and external stimuli.

    • Awareness of Internal Stimuli: Includes sensations such as pain, hunger, thirst, sleepiness, and awareness of our thoughts and emotions.

    • Awareness of External Stimuli: Includes experiences like seeing light, feeling warmth, or hearing voices.

  • Continuum of Consciousness: Consciousness can be viewed as a continuum ranging from full awareness to deep sleep.

  • States of Consciousness:

    • Sleep: A state characterized by relatively low levels of physical activity and reduced sensory awareness, distinct from periods of rest during wakefulness.

    • Wakefulness: Characterized by high levels of sensory awareness, thought, and behavior.

    • Other States: Daydreaming, intoxication, and unconsciousness due to anesthesia are also different states of consciousness.

  • Partial Awareness: We are not always completely aware of our surroundings even when awake (e.g., daydreaming while driving, performing complex tasks without conscious thought). Many such processes are rooted in biology.

Biological Rhythms

  • Definition: Internal rhythms of biological activity.

  • Examples:

    • Menstrual Cycle: A recurring, cyclical pattern of bodily changes lasting approximately 28 days (a lunar month).

    • Body Temperature Fluctuation: Cyclical changes over a 24-hour period. Alertness is associated with higher body temperatures, while sleepiness is associated with lower body temperatures.

Circadian Rhythms

  • Definition: A biological rhythm that takes place over a period of about 24 hours.

  • Examples:

    • Sleep-Wake Cycle: The most evident example, linked to the environment's natural light-dark cycle.

    • Daily Fluctuations in: Heart rate, blood pressure, blood sugar, and body temperature.

  • Role in Consciousness: Some circadian rhythms directly influence changes in our state of consciousness.

The Biological Clock

  • Brain Mechanism: The brain's internal clock mechanism is located in the hypothalamus, specifically in the suprachiasmatic nucleus (SCN).

    • The hypothalamus is a main center of homeostasis, which is the tendency to maintain balance or an optimal level within a biological system.

  • Synchronization with External World: Axons of light-sensitive neurons in the retina provide light information to the SCN, allowing this internal clock to synchronize with the outside world (Klein, Moore, & Reppert, 1991; Welsh, Takahashi, & Kay, 2010). This ensures that, generally, circadian cycles align with the daily environment (e.g., sleeping at night, being awake during the day).

Melatonin and Sleep Regulation

  • Melatonin: A hormone that is a crucial regulator of sleep-wake cycles.

  • Pineal Gland: An endocrine structure inside the brain that releases melatonin.

    • Involved in regulating various biological rhythms and the immune system during sleep (Hardeland, Pandi-Perumal, & Cardinali, 2006).

    • Melatonin Release: Stimulated by darkness and inhibited by light.

  • Chronotype: Refers to individual differences in circadian patterns of activity.

    • Examples: