Circadian rhythm
physical, mental, and behavioral changes that follow a 24-hour cycle
Dreams
a series of thoughts, images, and sensations occurring in a person's mind during sleep.
Electroencephalograph (EEG)
a machine used for electroencephalography.
Hypersomnia
medical conditions in which you repeatedly feel excessively tired during the day (called excessive daytime sleepiness) or sleep longer than usual at night
Insomnia
a common sleep disorder
Melatonin
a hormone that your brain produces in response to darkness
Napping
A midday nap can enhance alertness, mood, memory, and reduce stress
Narcolepsy
a chronic neurological disorder that affects the brain's ability to control sleep-wake cycles
Night Terrors
a sleep disorder in which a person quickly awakens from sleep in a terrified state
Nightmares
a frightening or unpleasant dream.
Parasomnia
occur in a state that lies between sleep and wakefulness
Restless Legs Syndrome
a condition that causes an uncontrollable urge to move the legs, usually because of an uncomfortable sensation
Sleep
a condition of body and mind that typically recurs for several hours every night, in which the eyes are closed, the postural muscles relaxed, the activity of the brain altered, and consciousness of the surroundings practically suspended.
Sleep apnea
a potentially serious sleep disorder in which breathing repeatedly stops and starts
Sleep deprivation
inadequate or insufficient sleep sustained over a period of time
Sleep paralysis
a temporary inability to move or speak that occurs directly after falling asleep or waking up
Sleep study
painless tests that measure how well you sleep and how your body responds to sleep problems
Snoring
caused by the rattling and vibration of tissues. View Source near the airway in the back of the throat
Stage 1 (Non-REM) sleep
heartbeat, eye movements, brain waves, and breathing activity begin to taper down
Stage 2 (Non-REM) sleep
a continued slowing of heartbeat, breathing, muscle activity, and eye movements.
Stage 3 (Non-REM) sleep
N3 or deep sleep,
Stage 4 (REM Sleep)
your voluntary muscles become immobilized.
Somnambulism
sleepwalking.
Wakefulness
a daily recurring brain state and state of consciousness in which an individual is conscious and engages in coherent cognitive and behavioral responses to the external world.