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.
Electroencephalograph (EEG)
a recording of brain activity
Hypersomnia
the inability to stay awake and alert during the day despite having more than an adequate amount of nighttime sleep.
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
Excessive daytime sleepiness. People with narcolepsy fall asleep without warning. It can happen anywhere and at any time
Night Terrors
feelings of great fear experienced on suddenly waking in the night.
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
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
a feeling of being conscious but unable to move
Sleep study
a test used to diagnose sleep disorders
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
a continued slowing of heartbeat, breathing, muscle activity, and eye movements.
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
not sleeping or able to sleep : sleepless.