week 10: wakefulness & sleep

Adult Sleep Requirement Myth

The belief that adults only need five hours of sleep to function properly.

Adult Sleep Requirement Fact

Adults generally need 7-9 hours of sleep per night for optimal cognitive function, immune support, and overall well-being.

Chronic Sleep Deprivation Risks

Impaired judgment, weakened immune response, and increased risk of heart disease and diabetes.

Nightlight and Melatonin Fact

Sleeping with a nightlight can disrupt melatonin production because artificial light reduces melatonin levels.

Blue Light Impact

Light from screens (phones, tablets, computers) mimics daylight and suppresses melatonin production more than other light types.

Alcohol and Sleep Myth

The belief that drinking alcohol before bed helps you sleep better.

Alcohol and Sleep Fact

Alcohol may help you fall asleep faster but disrupts sleep quality by interfering with REM sleep, leading to frequent awakenings and grogginess.

Brain Activity During Sleep Myth

The belief that the brain is completely inactive during sleep.

Brain Activity During Sleep Fact

The brain is highly active during sleep, especially during REM, for memory consolidation, learning, and emotional processing.

Weekend "Catch-up" Sleep Myth

The belief that you can fully restore the effects of chronic sleep deprivation by sleeping longer on weekends.

Weekend "Catch-up" Sleep Fact

Inconsistent sleep schedules lead to metabolic issues and mood disturbances; a consistent daily schedule is the best approach.

Sleep-Wake Cycle

A 24-hour cycle essential for maintaining mental and physical health.

Circadian Rhythms

Biological processes cycling approximately every 24 hours, influencing sleep, wakefulness, body temperature, and hormone release.

Suprachiasmatic Nucleus (SCN)

The primary "biological clock" located in the hypothalamus that receives light input to synchronize rhythms.

Endogenous Biological Rhythm Evidence

Animals and humans (including astronauts) maintain ~24-hour cycles even in constant darkness or light, proving the rhythm is self-regulated.

Cortisol

A hormone released in the morning by the biological clock to increase alertness and promote wakefulness.

Melatonin

A hormone released by the pineal gland in the evening to induce sleepiness; production is suppressed by light.

Pontomesencephalon

A brainstem area that activates the cerebral cortex to promote arousal and wakefulness.

Basal Forebrain

An area near the base of the forebrain that releases acetylcholine to maintain wakefulness and cortical arousal.

Locus Coeruleus

A small area in the pons that releases norepinephrine to maintain attention and alertness; it is least active during sleep.

Acetylcholine (ACh)

A neurotransmitter critical for cortical arousal and the regulation of REM sleep.

GABA (Gamma-Aminobutyric Acid)

An inhibitory neurotransmitter essential for initiating and maintaining sleep by suppressing brain activity.

Histamine

A neurotransmitter that promotes wakefulness, alertness, and sustained attention.

Orexin

A key neurotransmitter that stabilizes the transition between sleep and wakefulness; deficiency is linked to narcolepsy.

Serotonin

A neurotransmitter that is higher during wakefulness and lower during REM sleep to allow for dreaming and memory processing.

Norepinephrine

A neurotransmitter active during wakefulness for alertness that diminishes during REM to allow for muscle paralysis.

Adenosine

A neurotransmitter that promotes sleep; its receptors are blocked by caffeine to increase alertness.

NREM Sleep

Non-Rapid Eye Movement sleep, consisting of stages 1 through 4.

Stage 1 (Light Sleep)

A brief transition phase with irregular, low-voltage brain waves where muscles relax and heart rate decreases.

Stage 2 (Deeper Sleep)

A stage marked by sleep spindles and K-complexes, accounting for a significant portion of the sleep cycle.

Sleep Spindles

Sudden bursts of rapid brain activity in Stage 2 involved in memory processing and arousal regulation.

K-complexes

Large brain waves in Stage 2 that protect sleep by blocking out external stimuli.

Slow-Wave Sleep (SWS)

Stages 3 and 4 characterized by large-amplitude, slow brain waves; essential for physical restoration and muscle repair.

Stage 4 Characteristics

The deepest and most restorative phase of sleep, prominent in early cycles and crucial for immune function.

REM Sleep (Paradoxical Sleep)

A stage with high brain activity and rapid eye movements, but accompanied by muscle atonia (paralysis).

Muscle Atonia

The paralysis of voluntary muscles during REM sleep to prevent acting out dreams.

PGO Waves

High-frequency waves (Ponto-geniculo-occipital) originating in the pons that spread to the occipital cortex; involved in dream imagery.

Limbic System Activity in REM

High activity in this emotional center explains why dreams are often vivid and emotional.

Brain Areas Deactivated in REM

The motor cortex and prefrontal cortex show reduced activity to prevent voluntary movement and rational thought.

Insomnia

Difficulty falling or staying asleep, often caused by stress, anxiety, or circadian disruptions.

Sleep Apnea

A disorder where breathing repeatedly stops and starts, often due to throat muscles relaxing and blocking the airway (OSA).

Narcolepsy

A neurological disorder characterized by uncontrollable daytime sleep attacks, often linked to orexin deficiency.

Cataplexy

A sudden loss of muscle control triggered by strong emotions, often seen in narcolepsy.

Sleep Paralysis

Temporary inability to move or speak when falling asleep or waking up.

Periodic Limb Movement Disorder (PLMD)

Involuntary, rhythmic leg movements during NREM sleep that cause fragmented sleep and fatigue.

REM Behavior Disorder (RBD)

A condition where muscle paralysis is absent during REM, causing individuals to physically act out dreams.

Somnambulism (Sleepwalking)

An NREM disorder involving walking or performing complex tasks while asleep without awareness.

Night Terrors

Sudden, intense fear and screaming during deep NREM sleep, common in children.

Jet Lag

A misalignment between the internal biological clock and the external environment caused by crossing time zones.

Physical Restoration Function

Occurs during deep sleep (SWS) when growth hormones are released for tissue repair and immune support.

Mental Restoration Function

Sleep transfers short-term memories from the hippocampus to the neocortex for long-term storage.

REM Function

Critical for emotional regulation, consolidation of procedural memories, creativity, and problem-solving.