sleep and dreams

Vocabulary flashcards covering key terms, devices, stages, rhythms, and health concepts related to sleep and dreaming.

Normal Waking Consciousness (NWC)

A state in which an individual is awake, alert, and aware of external stimuli and internal thoughts.

Altered States of Consciousness (ASC)

Conditions that differ noticeably from NWC in levels of awareness, perception, and experience; they can occur naturally or be deliberately induced.

Sleep (as a state)

A naturally occurring altered state of consciousness experienced roughly every 24 hours, characterized by reduced awareness and responsiveness.

Sleep–wake cycle

The recurring daily pattern of sleep and wakefulness that typically follows a 24-hour schedule.

Circadian rhythm

A biological rhythm with a period of about 24 hours that regulates physiological processes such as the sleep–wake cycle.

Suprachiasmatic nucleus (SCN)

A cluster of cells in the hypothalamus that receives light information and regulates circadian rhythms by controlling melatonin release.

Melatonin

A hormone released by the pineal gland; higher levels promote drowsiness, lower levels promote alertness.

Ultradian rhythm

A biological rhythm shorter than 24 hours, such as heartbeat, hunger cycles, and individual sleep cycles.

Sleep cycle

A complete progression through NREM stages 1–3 followed by REM sleep, lasting about 90 minutes.

Non-REM (NREM) sleep

Sleep stages 1–3; primarily restorative for the body and important for procedural memory consolidation.

Stage 1 NREM

Lightest sleep lasting 2–10 min; alpha and theta waves; easy to awaken; HR and breathing begin to slow.

Stage 2 NREM

Most frequently experienced stage (≈50 % of total sleep); theta waves; HR, breathing, and temperature drop; lasts 20–30 min.

Stage 3 NREM (Slow-wave sleep)

Deep sleep dominated by delta waves; hardest to awaken; night terrors and sleep-walking most likely here.

Rapid Eye Movement (REM) sleep

Brain-active stage with beta-like saw-tooth waves; vivid dreaming, muscle paralysis, eye movements; ≈20 % of total sleep.

Sleep paralysis

Temporary inability to move voluntary muscles during REM due to natural muscular atonia.

Procedural memory consolidation

Strengthening of motor‐skill memories that occurs mainly during NREM sleep.

EEG (Electroencephalograph)

Device that detects, amplifies, and records the brain’s electrical activity in brainwave patterns.

EMG (Electromyograph)

Device that detects, amplifies, and records the electrical activity of skeletal muscles; low activity indicates REM sleep.

EOG (Electro-oculograph)

Device that detects, amplifies, and records electrical activity of muscles controlling eye movement; high activity marks REM sleep.

Brainwave frequency

The number of brainwave cycles per second; higher frequency indicates faster brain activity.

Brainwave amplitude

The height or intensity of brainwaves; higher amplitude indicates stronger electrical signals.

Alpha waves

Medium-frequency, low-amplitude waves linked with relaxed wakefulness and the transition to sleep.

Beta waves

High-frequency, low-amplitude waves associated with alert wakefulness and REM dreams.

Theta waves

Medium-frequency, medium-amplitude waves typical of stages 1 and 2 NREM sleep.

Delta waves

Low-frequency, high-amplitude waves characteristic of deep, slow-wave sleep (stage 3 NREM).

Saw-tooth waves

Distinctive jagged beta-like waves seen during REM sleep, accompanying vivid dreaming.

Sleep hygiene

The collection of habits, behaviours, and environmental conditions that promote consistent, high-quality sleep.

Physiological sleep factors

Internal bodily conditions (e.g., hormones, health, genetics) influencing sleep quality.

Behavioural sleep factors

Actions or habits (e.g., bedtime routines, screen use) that affect sleep.

Emotional sleep factors

Feelings or mental states (e.g., stress, anxiety) that impact sleep onset and continuity.

Environmental sleep factors

Physical characteristics of the sleep space (e.g., light, noise, temperature).

Sleep stability

Consistency and regularity of one’s sleep schedule and circadian alignment.

Daytime factors

Daytime activities (e.g., exercise, caffeine intake, naps) that influence nighttime sleep.

Healthy sleep hygiene practices

Behaviours like a regular schedule, relaxing routine, limiting screens/caffeine, and maintaining a cool, dark room.

Poor sleep hygiene practices

Habits such as irregular bedtimes, device use in bed, late caffeine/alcohol, and bright/noisy bedrooms.

Recommended sleep hours – Infants

Approximately 12–16 hours of sleep per 24 hours, supporting rapid growth and brain development.

Recommended sleep hours – Teens

Roughly 8–10 hours nightly, accommodating hormonal shifts and high developmental demands.

Recommended sleep hours – Adults

About 7–9 hours per night, sustaining physical health, cognition, and mood.

Sleep deprivation

A state of insufficient or poor-quality sleep.

Impacts of sleep deprivation

Includes impaired cognition, mood disturbances, higher accident risk, weakened immunity, and long-term health issues.

Causes of sleep deprivation

Biological (genes, hormones), environmental (noise, light, shift work), and lifestyle (caffeine, stress, inactivity) factors.