Circadian rhythm
the 24-hour internal clock in our brain that regulates cycles of alertness and sleepiness by responding to light changes in our environment.
Dreams
a series of thoughts, images, and sensations occurring in a person's mind during sleep."I had a recurrent dream about falling from great heights"
Electroencephalograph (EEG)
a recording of brain activity
Hypersomnia
the inability to stay awake and alert during the day
Insomnia
habitual sleeplessness; inability to sleep.
Melatonin
a hormone secreted by the pineal gland which inhibits melanin formation and is thought to be concerned with regulating the reproductive cycle.
Napping
sleep lightly or briefly, especially during the day.
Narcolepsy
a condition characterized by an extreme tendency to fall asleep whenever in relaxing surroundings.
Night Terrors
Night terrors are a sleep disorder in which a person quickly awakens from sleep in a terrified state.
Nightmares
a frightening or unpleasant dream.
Parasomnia
An abnormal disruption of sleep, such as sleep walking, sleep talking, nightmares, bedwetting, sleep apnea (problems with breathing that cause loud snoring), or nighttime seizures
Restless Legs Syndrome
a disorder characterized by the occurrence of uncomfortable sensations in the legs and the urge to move them in order to relieve the sensations, typically occurring in the evening or at night and often interfering with sleep.
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
Sleep apnea is a potentially serious sleep disorder in which breathing repeatedly stops and starts.
Sleep deprivation
the situation or condition of suffering from a lack of sleep.
Sleep paralysis
When you wake up suddenly from REM, your brain is awake, but your body is still in REM mode and can't move, causing you to feel like you're paralyzed.
Sleep study
a test that records the activity of the body during sleep.
Snoring
the action or fact of making a snorting or grunting sound while asleep.
Stage 1 (Non-REM) sleep
the first sleep stage you enter when nodding off.
Stage 2 (Non-REM) sleep
still light sleep, but deeper than stage 1.
Stage 3 (Non-REM) sleep
a period of deep sleep where any environmental noises or activity may fail to wake the sleeping person
Stage 4 (REM Sleep)
the stage of sleep where most dreams happen.
Somnambulism
sleepwalking.
Wakefulness
the condition of not sleeping or being unable to sleep.