Circadian rhythm

the physical, mental, and behavioral changes an organism experiences over 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

a condition in which you feel extreme daytime sleepiness despite getting sleep that should be adequate

Insomnia

a common sleep disorder With insomnia, you may have trouble falling asleep, staying asleep, or getting good quality sleep

Melatonin

a hormone that your brain produces in response to darkness

Napping

a short period of sleep, typically taken during daytime hours as an adjunct to the usual nocturnal sleep period.

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 disturbing dream associated with negative feelings, such as anxiety or fear that awakens you.

Parasomnia

occur in a state that lies between sleep and wakefulness.

Restless Legs Syndrome

a condition that causes a very strong urge to move the legs.

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

occurs when an individual fails to get the amount of sleep that they need

Sleep paralysis

a temporary inability to move or speak that occurs directly after falling asleep or waking up

Sleep study

a test used to diagnose sleep disorders

Snoring

the hoarse or harsh sound that occurs when air flows past relaxed tissues in your throat, causing the tissues to vibrate as you breathe

Stage 1 (Non-REM) sleep

heartbeat, eye movements, brain waves, and breathing activity begin to taper down

Stage 2 (Non-REM) sleep

Stage 2 is still light sleep, but deeper than stage 1.

Stage 3 (Non-REM) sleep

deep sleep,

Stage 4 (REM Sleep)

the cycle where we dream

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