Circadian rhythm
the body's internal 24-hour clock that regulates the sleep-wake cycle
Dreams
a subjective experience that most commonly occur during REM sleep, and can be caused by the brain processing daily information, re-experiencing memories, or other random signals
Electroencephalograph (EEG)
a medical test that measures the electrical activity of the brain.
Hypersomnia
a condition characterized by excessive daytime sleepiness, where individuals feel drowsy and need to sleep more than usual, even after getting enough rest
Insomnia
Insomnia
Melatonin
a hormone that helps regulate the sleep-wake cycle, and it is also available as a supplement to help with sleep problems like insomnia and jet lag
Napping
a short sleep during the day that can boost mood, alertness, and productivity
Narcolepsy
a chronic sleep disorder characterized by excessive daytime sleepiness and sudden "sleep attacks" that significantly impact daily life
Night Terrors
episodes of screaming, thrashing, and panic that occur during deep sleep, causing the person to seem terrified but remain unresponsive to being woken
Nightmares
disturbing dreams that can cause feelings of fear, anxiety, or sadness, and often cause the sleeper to wake up
Parasomnia
a sleep disorder characterized by abnormal behaviors, movements, or experiences that occur during sleep or while transitioning between sleep and wakefulness
Restless Legs Syndrome
a neurological disorder causing an irresistible urge to move your legs, often accompanied by uncomfortable sensations like crawling, tingling, or aching
Sleep
a vital biological process for physical and mental health, during which the brain and body are active, processing information, forming memories, and repairing cells
Sleep apnea
a disorder where breathing repeatedly stops and starts during sleep, causing poor sleep quality and potential health complications
Sleep deprivation
when you aren't sleeping enough, or you aren't getting good, quality sleep
Sleep paralysis
temporary inability to move or speak while waking up or falling asleep, often accompanied by terrifying hallucinations or a feeling of pressure on the chest
Sleep study
a medical test that records brain waves, heart rate, oxygen levels, and other body functions while you sleep
Snoring
a sound caused by the vibration of relaxed throat tissues as air passes through the upper airway during sleep
Stage 1 (Non-REM) sleep
the initial, light stage of sleep that transitions you from wakefulness to sleep
Stage 2 (Non-REM) sleep
a light stage of sleep where the heart rate and breathing slow down, the body temperature drops, and eye movements stop
Stage 3 (Non-REM) sleep
the deepest stage of sleep, where the body repairs and regenerates tissues, builds bone and muscle, and strengthens the immune system
Stage 4 (REM Sleep)
the final and most active stage of the sleep cycle
Somnambulism
when people get up and walk around while asleep
Wakefulness
the state of being awake, alert, and conscious of one's surroundings