front 1 Circadian rhythm | back 1 the body's natural 24-hour cycle that regulates physical, mental, and behavioral changes, primarily the sleep-wake cycle. |
front 2 Dreams | back 2 a series of thoughts, images, and sensations occurring in a person's mind during sleep. |
front 3 Electroencephalograph (EEG) | back 3 a test that records the electrical activity of the brain by placing small metal disks called electrodes on the scalp. |
front 4 Hypersomnia | back 4 a sleep disorder characterized by excessive daytime sleepiness and a persistent need to sleep, even after a full night's rest. |
front 5 Insomnia | back 5 persistent difficulty falling or staying asleep, or waking up too early, even when an opportunity for sleep is present. |
front 6 Melatonin | back 6 a hormone produced in the brain that regulates the body's circadian rhythm, or sleep-wake cycle. |
front 7 Napping | back 7 the practice of sleeping for a short time during what would otherwise be a long stretch of wakefulness. |
front 8 Narcolepsy | back 8 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. |
front 9 Night Terrors | back 9 episodes of screaming, thrashing, and panic that happen during deep non-REM sleep. |
front 10 Nightmares | back 10 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. |
front 11 Parasomnia | back 11 a sleep disorder characterized by abnormal, unpleasant events or behaviors that occur during sleep, falling asleep, or waking up. |
front 12 Restless Legs Syndrome | back 12 a neurological disorder causing an uncontrollable urge to move your legs, typically due to uncomfortable sensations like creeping, tingling, or aching. |
front 13 Sleep | back 13 a state of reduced mental and physical activity in which consciousness is altered and certain sensory activity is inhibited. |
front 14 Sleep apnea | back 14 a sleep disorder where breathing repeatedly stops and starts during sleep, typically for 10 seconds or more, occurring at least 5 times an hour. |
front 15 Sleep deprivation | back 15 occurs when an individual fails to get the amount of sleep that they need. |
front 16 Sleep paralysis | back 16 a temporary inability to move or speak while falling asleep or waking up, a condition that can be accompanied by terrifying hallucinations. |
front 17 Sleep study | back 17 a medical test that monitors your body's activity while you sleep to diagnose sleep disorders. |
front 18 Snoring | back 18 the noisy, vibrating sound produced when breathing during sleep is restricted. |
front 19 Stage 1 (Non-REM) sleep | back 19 the lightest stage of sleep, acting as a transition from wakefulness to sleep. |
front 20 Stage 2 (Non-REM) sleep | back 20 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. |
front 21 Stage 3 (Non-REM) sleep | back 21 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. |
front 22 Stage 4 (REM Sleep) | back 22 he stage where most dreaming occurs, characterized by high brain activity similar to being awake, rapid eye movements, and temporary muscle paralysis. |
front 23 Somnambulism | back 23 the medical term for sleepwalking, which involves walking or performing other activities while remaining in a state of sleep. |
front 24 Wakefulness | back 24 the state of being awake, conscious, alert, and responsive to your surroundings. |