Which hormone helps regulate the sleep-wake cycle?
AnswerMelatonin
Melatonin rises in the evening as it gets dark.
Health · Facts & stats
Rest facts & stats
7 fact-checked facts about rest, sleep and recovery, each with the reason behind it. 5 more are in today's round and join this page after it closes.
The basics
What is the body's roughly 24-hour internal clock called?
AnswerCircadian rhythm
Circadian rhythms guide sleep, alertness and many body processes.
Going deeper
Which gland produces melatonin?
AnswerPineal gland
The small pineal gland in the brain releases melatonin.
About how long is one full sleep cycle?
AnswerAbout 90 minutes
Adults cycle through sleep stages roughly every 90 minutes.
Deep sleep is also known as what?
AnswerSlow-wave sleep
Deep sleep shows slow delta brain waves.
Expert level
Where is the brain's master circadian clock located?
AnswerThe suprachiasmatic nucleus of the hypothalamus
The SCN responds to light signals from the eyes.
How many stages of non-REM sleep does the current standard scoring system define?
AnswerThree
Sleep scoring defines N1, N2 and N3 as the non-REM stages.
Know these cold?Today's round is five questions like these, 20 seconds each. Your streak and level follow you to every arena.Play today's round