Circadian rhythm

A circadian rhythm, or circadian cycle, is a natural oscillation that repeats roughly every 24 hours. Circadian rhythms can refer to any process that originates within an organism and responds to the environment.

Dreams

A dream is a succession of images, ideas, emotions, and sensations that usually occur involuntarily in the mind during certain stages of sleep. Humans spend about two hours dreaming per night, and each dream lasts around 5 to 20 minutes, although the dreamer may perceive the dream as being much longer than this.

Electroencephalograph (EEG)

Electroencephalography is a method to record an electrogram of the spontaneous electrical activity of the brain. The biosignals detected by EEG have been shown to represent the postsynaptic potentials of pyramidal neurons in the neocortex and allocortex.

Hypersomnia

Hypersomnia refers to medical conditions in which you repeatedly feel excessively tired during the day (called excessive daytime sleepiness) or sleep longer than usual at night. It is different from feeling tired due to lack of or interrupted sleep at night.

Insomnia

Insomnia is a common sleep disorder. With insomnia, you may have 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. Insomnia can get in the way of your daily activities and may make you feel sleepy during the day.Mar 24, 2022

Melatonin

Melatonin is a hormone that your brain produces in response to darkness. It helps with the timing of your circadian rhythms (24-hour internal clock) and with sleep. Being exposed to light at night can block melatonin production. Research suggests that melatonin plays other important roles in the body beyond sleep.

Napping

Key Takeaways. A midday nap can enhance alertness, mood, memory, and reduce stress. Choose a comfortable, quiet spot and time your naps well to avoid grogginess. The ideal nap length, between 20 and 30 minutes, should help you wake up feeling refreshed without falling into deep sleep

Narcolepsy

What is narcolepsy? Narcolepsy is a chronic neurological disorder that affects the brain's ability to control sleep-wake cycles. People with narcolepsy may feel rested after waking, but then feel very sleepy throughout much of the day.Sep 20, 2023

Night Terrors

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

Nightmares

a bad dream

Parasomnia

Parasomnias occur in a state that lies between sleep and wakefulness. A person with parasomnias may seem to be alert, walking or talking or eating or doing other such activities but without awareness because the brain is only partially awake.

Restless Legs Syndrome

What is restless legs syndrome? Restless legs syndrome (RLS)—also known as Willis-Ekbom Disease, primary RLS, and idiopathic RLS—is a neurological disorder that causes unpleasant or uncomfortable sensations in your legs and an irresistible urge to move them.Sep 20, 2023

Sleep

napping in the night.

Sleep apnea

Sleep apnea is a potentially serious sleep disorder in which breathing repeatedly stops and starts. If you snore loudly and feel tired even after a full night's sleep, you might have sleep apnea.Apr 6, 2023

Sleep deprivation

Sleep deprivation is a condition characterised by inadequate or insufficient sleep sustained over a period of time. It occurs when an individual consistently fails to obtain the amount of sleep that they need.

Sleep paralysis

Sleep paralysis is a temporary inability to move or speak that occurs directly after falling asleep or waking up. While the states of sleep and wakefulness are usually clearly defined and distinct, conditions like sleep paralysis can blur these boundaries.Oct 26, 2023

Sleep study

Sleep studies, also called polysomnography, are painless tests that measure how well you sleep and how your body responds to sleep problems. They are also used to help your doctor diagnose sleep disorders.Mar 24, 2022

Snoring

What Causes Snoring? Snoring is caused by the rattling and vibration of tissues. View Source near the airway in the back of the throat. During sleep, the muscles loosen, narrowing the airway. As a person inhales and exhales, the moving air causes the tissue to flutter and make noise.6 days ago

Stage 1 (Non-REM) sleep

Stage 1 NREM sleep is the first sleep stage you enter when nodding off. This sleep stage is when heartbeat, eye movements, brain waves, and breathing activity begin to taper down. Motor movements also diminish, although you may experience muscle twitches called hypnic jerks.Nov 3, 2023

Stage 2 (Non-REM) sleep

Stage 2 NREM sleep sees a continued slowing of heartbeat, breathing, muscle activity, and eye movements. During this stage, you also experience a reduction in body temperature. Throughout the course of the night, you spend about half the time in stage 2 sleep.Nov 3, 2023

Stage 3 (Non-REM) sleep

Stage 3. Stage 3 sleep is also known as N3 or deep sleep, and it is harder to wake someone up if they are in this phase. Muscle tone, pulse, and breathing rate decrease in N3 sleep as the body relaxes even further. The brain activity during this period has an identifiable pattern of what are known as delta waves.Nov 3, 2023

Stage 4 (REM Sleep)

Stage 4 is an even deeper sleep where the brain waves further slow and sleepers are very difficult to wake. It's believed that tissue repair occurs during the stage of sleep and that hormones are also released to help with growth.

Somnambulism

sleepwalking.

Wakefulness

results (0.30 seconds) Search ResultsFeatured snippet from the webWakefulness is 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.