circadian rhythm

physical, mental, and behavioral changes that follow a 24-hour cycle

Dreams

a succession of images, ideas, emotions, and sensations that usually occur involuntarily in the mind during certain stages of sleep

Electroencephalograph (EEG)

a medical test used to measure the electrical activity of the brain

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

trouble falling asleep, staying asleep, or getting good quality sleep. This happens even if you have the time and the right environment to sleep well

Melatonin

a hormone that your brain produces in response to darkness

Napping

short and meant to give you a bit of rest

Narcolepsy

a chronic neurological disorder that affects the brain's ability to control sleep-wake cycles

Night Terrors

Episodes of screaming, intense fear, and flailing while still asleep, often paired with sleepwalking

Nightmares

Frightening dreams, usually during REM sleep, that are normal and common in children under 10 and can also affect teens and adults.

Parasomnia

occur in a state that lies between sleep and wakefulness

Restless Legs Syndrome

typically occurs while sitting or lying down. It generally worsens with age and can disrupt sleep

Sleep

a state of reduced mental and physical activity in which consciousness is altered and sensory activity is inhibited to a certain extent

Sleep apnea

A potentially serious sleep disorder in which breathing repeatedly stops and starts.

Sleep deprivation

means you're not getting enough sleep

Sleep paralysis

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

Sleep study

a test that records the activity of the body during sleep

Snoring

Hoarse or harsh sound from nose or mouth that occurs when breathing is partially obstructed while sleeping.

Stage 1 (Non-REM) sleepw

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

known as N3 or deep sleep

Stage 4 (REM Sleep)

your voluntary muscles become immobilized

Somnambulism

The act of getting up and walking around while asleep.

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.