Topic 1.5 : Sleep

Consciousness

Your awareness of your thoughts, feelings, and surroundings.

Sleep

A natural state of rest for the body and mind, characterized by altered consciousness, reduced sensory activity, and inactivity of nearly all voluntary muscles.

Circadian Rhythm

Your biological clock: 24-hour body clock that helps regulate the sleep–wake cycle and regular bodily rhythms.

The Suprachiasmatic Nucleus (SCN)

The brain’s master clock in the hypothalamus that regulates circadian rhythms, such as the sleep-wake cycle.

NREM (Non-Rapid Eye Movement) Sleep

The sleep stages characterized by slow brain waves, relaxed muscles, and decreased heart rate and breathing.

NREM1

Light sleep stage characterized by hypnagogic sensations, lasting 5-10 minutes with alpha waves.

Alpha Waves

The relatively slow brain waves associated with NREM1.

Hypnagogic Sensations

Brief, vivid sensations as you’re falling asleep, like a jerk or the feeling of falling.

NREM2

Deeper sleep stage characterized by sleep spindles on an EEG, lasting 10-25 minutes with theta waves.

Theta Waves

Low-frequency, high-amplitude brain waves that are associated with NREM2.

Sleep Spindles

Short bursts of rapid brain-wave activity seen in NREM2 sleep.

K-Complexes

Large, high-amplitude brain waves in NREM2 that can occur in response to stimuli.

NREM3

The deepest sleep stage, also known as slow-wave sleep, characterized by delta waves.

Delta Waves

Very slow, high-amplitude brain waves that are associated with NREM3

REM (Rapid Eye Movement) Sleep

Also known as paradoxical sleep, where most dreaming occurs and an EEG shows brain activity similar to awareness.

Muscle Atonia

The temporary paralysis of most muscles during REM sleep.

REM Reboud

The tendency for REM sleep to increase following REM sleep deprivation.

Activation-Synthesis Theory

A theory of dreaming that suggests dreams are the brain's attempt to make sense of random neural activity.

Memory Consolidation Theory

The theory that sleep and dreaming helps strengthen the neural connections that form our memories.

Insomnia

Ongoing difficulty falling asleep, staying asleep, or both.

Narcolepsy

A sleep disorder with sudden, uncontrollable sleep attacks; often includes cataplexy.

Sleep Apnea

A disorder where breathing repeatedly stops during sleep, fragmenting rest.

REM Sleep Behavior Disorder

Acting out dreams due to lack of muscle paralysis

Somnambulism

Sleepwalking, typically occurring during deep NREM Stage 3 sleep.