Unit 4 Psychology – Chapter 6: The Demand for Sleep

Vocabulary flashcards covering key terms from Chapter 6 on consciousness, measurement of sleep, biological rhythms, and sleep stages across the lifespan.

Consciousness

Our awareness of external objects and events, internal sensations, thoughts, feelings and our own existence at any given time.

Normal Waking Consciousness (NWC)

The state of being awake and aware of internal thoughts, feelings and external stimuli.

Altered State of Consciousness (ASC)

Any state distinctly different from NWC in self-awareness, perception, self-control, emotional awareness and sense of time or place.

Consciousness Continuum

A visual scale that places different states of consciousness from total awareness to no awareness, showing how we move fluidly between them.

Naturally Occurring ASC

An altered state that arises without intentional effort, e.g., sleep, dreaming, day-dreaming, drowsiness.

Induced ASC

An altered state deliberately produced by an external aid or action, e.g., hypnosis, anaesthesia, meditation, drug use.

Sleep

A reversible, naturally occurring suspension of consciousness in which we disengage from perception and are unresponsive until awakened.

Psychological Construct

A concept used to describe a pattern of behaviour or activity that exists and can be measured, but cannot be directly observed (e.g., consciousness, sleep).

Electroencephalograph (EEG)

Device that Detects, Amplifies and Records Electrical activity of the brain (brainwaves).

Electromyograph (EMG)

Device that Detects, Amplifies and Records Electrical activity of the muscles.

Electro-oculargraph (EOG)

Device that Detects, Amplifies and Records Electrical activity of the muscles around the eyes.

Frequency (Brainwaves)

The number of brainwave cycles per second.

Amplitude (Brainwaves)

The height or intensity of a brainwave.

Beta Waves

High-frequency, low-amplitude waves associated with alert, busy thinking.

Alpha Waves

Moderately high frequency, low amplitude waves present when relaxed or almost asleep.

Theta Waves

Medium frequency, medium amplitude waves typical of light sleep.

Delta Waves

Low-frequency, high-amplitude waves characteristic of deep sleep.

DARE

Acronym for the EEG, EMG, EOG functions: Detects, Amplifies and Records Electrical activity.

Sleep Diary

A self-reported, qualitative record of an individual’s sleeping and waking patterns kept over weeks.

Video Monitoring

Infra-red video recording of a sleeper to observe movements, sounds or behaviours during a sleep episode.

Biological Rhythm

Cyclic changes in bodily activity that repeat over time, controlled by an internal ‘body clock’.

Circadian Rhythm

24-hour cycle in physiological processes, e.g., the sleep-wake cycle.

Ultradian Rhythm

A cycle shorter than 24 hours that repeats multiple times daily, e.g., a 90-minute sleep cycle or hunger waves.

Sleep-Wake Cycle

Endogenous circadian pattern determining when we feel sleepy and when we wake.

Melatonin

Hormone released by the pineal gland; increases in darkness to promote sleepiness and is suppressed by light.

Suprachiasmatic Nucleus (SCN)

Cluster of cells in the hypothalamus acting as the master body clock, regulating melatonin release and the sleep-wake cycle.

Zeitgeber

An external cue, such as light, that synchronises or entrains biological rhythms.

Negative Feedback Loop (Sleep)

Process by which the SCN monitors melatonin levels and adjusts release to maintain circadian timing.

Non-Rapid Eye Movement (NREM) Sleep

Sleep type comprising stages 1-3; important for physical restoration and making up ~80% of total sleep time.

Rapid Eye Movement (REM) Sleep

Sleep type with rapid eye movements, muscle atonia and vivid dreaming; about 20–25% of total sleep.

Sleep Cycle

A sequence of NREM stages 1-3 followed by REM, lasting ~90 minutes and repeating 5-6 times a night.

NREM Stage 1

Transition into sleep; light sleep with alpha to theta waves and possible hypnic jerks.

NREM Stage 2

Light ‘true’ sleep marked by theta waves, sleep spindles and K-complexes.

Sleep Spindle

Brief burst of high-frequency brainwaves seen in Stage 2, signalling true sleep.

K-Complex

Sudden high-amplitude brainwave in Stage 2 triggered by external stimuli.

NREM Stage 3

Deepest NREM stage with delta waves; hard to wake, physical restoration peaks.

Sleep Onset

The transition period from wakefulness to sleep.

Sleep Latency

The amount of time it takes to fall asleep after attempting to do so.

Hypnic Jerk

Involuntary muscle spasm often occurring during Stage 1 sleep.

Sleep Inertia

Grogginess and disorientation experienced when awakened from deep sleep.

Muscle Atonia

Loss of muscle tone during REM sleep, causing external paralysis.

Paradoxical Sleep

Another term for REM sleep: internally active brain with externally paralysed body.

Hypnogram

Graph showing stages of sleep across time during a sleep episode.

Delayed Sleep Onset (Adolescence)

Puberty-related shift causing teenagers to fall asleep later, often reducing total sleep time.

Newborn Sleep Pattern

Approximately 16 hours of sleep, with ~50% REM and 50% NREM.

Adolescent Sleep Pattern

About 9 hours sleep, typically 20% REM and 80% NREM.

Elderly Sleep Pattern

Around 6 hours sleep, frequent awakenings, ~20% or less REM, 80% NREM.