Circadian rhythm

the body's natural 24-hour cycle that regulates physical, mental, and behavioral changes, primarily the sleep-wake cycle.

Dreams

a series of thoughts, images, and sensations occurring in a person's mind during sleep.

Electroencephalograph (EEG)

a test that records the electrical activity of the brain by placing small metal disks called electrodes on the scalp.

Hypersomnia

a sleep disorder characterized by excessive daytime sleepiness and a persistent need to sleep, even after a full night's rest.

Insomnia

persistent difficulty falling or staying asleep, or waking up too early, even when an opportunity for sleep is present.

Melatonin

a hormone produced in the brain that regulates the body's circadian rhythm, or sleep-wake cycle.

Napping

the practice of sleeping for a short time during what would otherwise be a long stretch of wakefulness.

Narcolepsy

a chronic neurological disorder causing the brain to struggle with regulating sleep-wake cycles, which results in uncontrollable daytime sleepiness and sudden, irresistible urges to sleep.

Night Terrors

episodes of screaming, thrashing, and panic that happen during deep non-REM sleep.

Nightmares

a frightening or disturbing dream that is vivid enough to cause a person to awaken, often accompanied by intense emotions like fear, sadness, or anxiety.

Parasomnia

a sleep disorder characterized by abnormal, unpleasant events or behaviors that occur during sleep, falling asleep, or waking up.

Restless Legs Syndrome

a neurological disorder causing an uncontrollable urge to move your legs, typically due to uncomfortable sensations like creeping, tingling, or aching.

Sleep

a state of reduced mental and physical activity in which consciousness is altered and certain sensory activity is inhibited.

Sleep apnea

a sleep disorder where breathing repeatedly stops and starts during sleep, typically for 10 seconds or more, occurring at least 5 times an hour.

Sleep deprivation

occurs when an individual fails to get the amount of sleep that they need.

Sleep paralysis

a temporary inability to move or speak while falling asleep or waking up, a condition that can be accompanied by terrifying hallucinations.

Sleep study

a medical test that monitors your body's activity while you sleep to diagnose sleep disorders.

Snoring

the noisy, vibrating sound produced when breathing during sleep is restricted.

Stage 1 (Non-REM) sleep

the lightest stage of sleep, acting as a transition from wakefulness to sleep.

Stage 2 (Non-REM) sleep

a period of light sleep where brain waves slow, but are punctuated by brief bursts of electrical activity, and the body's heart rate and breathing slow down further as it prepares for deeper sleep.

Stage 3 (Non-REM) sleep

the deepest stage of sleep, also called slow-wave sleep, where the body performs restorative functions like tissue repair, muscle growth, and immune system strengthening.

Stage 4 (REM Sleep)

he stage where most dreaming occurs, characterized by high brain activity similar to being awake, rapid eye movements, and temporary muscle paralysis.

Somnambulism

the medical term for sleepwalking, which involves walking or performing other activities while remaining in a state of sleep.

Wakefulness

the state of being awake, conscious, alert, and responsive to your surroundings.