Sleep

Sleep

A naturally occurring, reversible altered state of consciousness characterized by reduced awareness.

Consciousness

Our awareness of internal thoughts, feelings, perceptions, and external environmental events.

Consciousness Continuum

The progression representing varying levels of awareness, from highly focused to unconscious.

Normal Waking Consciousness (NWC)

States of consciousness when we are awake and aware of internal and external environments.

Altered State of Consciousness (ASC)

Any state distinct from NWC, deviating in awareness, thoughts, feelings, or perceptions.

Normal waking consciousness examples

focused attention, divided attention

altered state of consciousness examples

daydreaming, meditation, alcohol induced, hypnosis, sleep, anaesthetised coma

Electroencephalograph (EEG)

A device that detects, amplifies, and records the electrical activity of the brain.

Brain Wave Types

beta, alpha, theta, and delta.

Electromyograph (EMG)

A device that detects, amplifies, and records electrical activity in skeletal muscles.

High EMG Activity

Indicates high muscle movement and physical alertness, typical of waking states.

Low EMG Activity

Indicates muscle relaxation, characteristic of deep sleep states.

Electro-oculograph (EOG)

A device that detects, amplifies, and records electrical activity of eye muscles.

EOG Activity in REM

high eye muscle activity

Sleep Diaries

Subjective self-report tools used to track sleep-wake patterns, habits, and perceived quality.

Video Monitoring

An objective tool recording externally observable physiological responses like movement and sound.

Circadian Rhythm

A biological rhythm that occurs approximately once every 24 hours.

Circadian Rhythm Influences

Primarily regulated by light levels and environmental time cues.

Suprachiasmatic Nucleus (SCN)

The master biological clock in the hypothalamus that regulates the sleep-wake cycle.

SCN Response to Light

Signals the body to raise temperature, increase cortisol, and suppress melatonin.

Melatonin

A sleep-inducing hormone released by the pineal gland.

Melatonin Regulation

Release is stimulated by darkness and suppressed by exposure to light.

Ultradian Rhythm

A biological rhythm with a cycle shorter than 24 hours.

NREM Sleep Functions

Responsible for physical recovery, waste removal, and replenishing neurotransmitters.

NREM Percentage

approximately 80% of total sleep time in adults.

NREM Distribution

first half of a sleep episode.

NREM Eye Movement

minimal to no eye movement.

NREM Brain Activity

The brain is active, but significantly less so than during REM or NWC.

NREM Stages

Consists of 3 distinct stages, ranging from light to deep sleep.

NREM Stage 1

A brief transition stage where we drift in and out of true sleep.

Hypnic Jerks

Involuntary muscle twitches that can occur during NREM Stage 1.

NREM Stage 2

A stage of light sleep where the individual is truly asleep.

NREM Stage 2 Physiology

Body temperature drops and heart rate begins to slow down.

NREM Stage 3

The deepest stage of sleep, where it is hardest to wake up.

NREM Stage 3 Phenomena

Stage where physical recovery occurs and sleepwalking or sleeptalking can happen.

REM Sleep Functions

Responsible for memory consolidation and strengthening neural connections.

REM Percentage

approximately 20% of total sleep time in adults.

REM Distribution

REM sleep periods increase in duration during the second half of sleep.

Paradoxical Sleep in REM

internal physiology is active while muscles are relaxed.

REM Eye Movement

rapid, jerky bursts of eye movement.

REM Brain Activity

Highly active brain wave patterns, similar to normal waking consciousness.

Sleep Cycle

A complete progression through NREM stages followed by a period of REM.

Sleep Cycle Duration

approximately 90 minutes.

Sleep Onset

The transition period from wakefulness to sleep, typically entering NREM Stage 1.

Aging Sleep Trend

Total sleep hours and sleep efficiency decrease as age increases.

Aging NREM Change

Deep NREM Stage 3 sleep decreases and is replaced by light NREM Stage 2.

Aging Awakenings

The frequency of waking up during the night increases with age.

Sleep Efficiency

The ratio of actual sleep time to total time spent in bed.

Newborn Sleep Duration

Newborns require approximately 16 hours of sleep per day.

Newborn Sleep Ratio

Consists of 50% REM sleep and 50% NREM sleep.

Why Newborns Need REM

To support constant learning and rapid neural pathway development.

Children Sleep Duration

approximately 10 to 12 hours of sleep per day.

Children Sleep Ratio

Consists of 25% REM sleep and 75% NREM sleep.

Why Children Need NREM 3

High amounts of NREM Stage 3 support physical growth and bone development.

Teenager Sleep Duration

approximately 8 to 10 hours of sleep per day.

Teenager Sleep Ratio

Consists of 20% REM sleep and 80% NREM sleep.

Teenager NREM 3 Purpose

Supports physical development and hormonal changes during puberty.

Adult Sleep Duration

approximately 7 to 9 hours of sleep per day.

Adult Sleep Ratio

Consists of 20% REM, 55% light NREM, and 25% deep NREM.

Why Adults Need Less NREM 3

Physical growth has stopped; sleep is for maintenance rather than growth.

Elderly Sleep Duration

The elderly require approximately 6 to 8 hours of sleep per day.

Elderly Sleep Ratio

Consists of 20% REM, very little NREM 3, and mostly light NREM 1 & 2.

Why Elderly Wake Up Often

A weakened SCN and difficulty generating slow delta waves lead to lighter sleep.

Partial Sleep Deprivation

Getting less than the required sleep quantity or missing specific sleep stages.

Affective Deprivation Symptoms

Mood disturbances, heightened anxiety, and lack of motivation.

Behavioural Deprivation Symptoms

Slowed reaction times, increased risk-taking, and clumsiness.

Cognitive Deprivation Symptoms

Shortened concentration span, poor problem-solving, and memory difficulties.

Physiological Deprivation Symptoms

Hand tremors, droopy eyelids, headaches, and slurred speech.

Total Sleep Deprivation

Going entirely without sleep for at least 24 hours.

Total Deprivation: Day 1

Characterized by mood shifts, mild clumsiness, and concentration difficulties.

Total Deprivation: Day 4

The onset of microsleeps to protect the brain from exhaustion.

Microsleep

Involuntary, brief periods of sleep lasting between 3 to 15 seconds.

Total Deprivation: Day 5

Can cause hallucinations, severe depression, and feelings of depersonalization.

Chronic Sleep Deprivation

Insufficient sleep over an extended period, such as weeks or months.

Chronic Deprivation Risks

Increased risk of depression, heart disease, obesity, and diabetes.

Sleep Debt

The cumulative deficit between required sleep and actual sleep obtained.

17-19 Hours Awake

Produces cognitive impairment equivalent to a BAC of 0.05.

24-28 Hours Awake

Produces cognitive impairment equivalent to a BAC of 0.10.

Circadian Rhythm Sleep Disorder

Sleep disruption caused by a mismatch between internal sleep-wake cycles and external demands.

Delayed Sleep Phase Syndrome (DSPS)

A disorder where the major sleep episode is delayed beyond conventional times.

DSPS Biological Cause

A delay in melatonin release and internal circadian timing.

DSPS Symptoms

Inability to fall asleep early, difficulty waking, and daytime sleepiness.

Advanced Sleep Phase Disorder

A disorder where the major sleep episode occurs earlier than conventional times.

Advanced Sleep Phase Cause

An abnormally early daily release of melatonin.

Shift Work

Work hours scheduled during natural sleep times, disrupting circadian rhythms.

Bright Light Therapy

Using high-intensity light exposure to advance or delay the sleep cycle.

Sleep Hygiene

Healthy behavioral practices that improve sleep quality and ease sleep onset.

Zeitgebers

External environmental cues that help synchronize and entrain circadian rhythms.

Entrainment

The process of resetting or adjusting biological rhythms to match external cues.

EOG in NREM sleep

low muscle activity