Sleep Basics
People spend about this fraction of their lives sleeping.
What is one-third?
This stage of sleep is when most dreaming happens.
What is REM sleep?
People who sleep less than this number of hours per night are more likely to get sick.
What is 6 hours?
This tall animal sometimes sleeps only about 30 minutes to 2 hours per day.
What is a Giraffe?
During sleep, this sense is the only major sense that stays mostly alert to help wake you if something important happens.
What is hearing?
Scientists say sleep is not just rest but a biological ______.
What is a necessity?
During REM sleep, your brain can be almost as active as when you are doing this.
What is being awake?
Sleep helps strengthen this body system that fights germs.
What is the immune system?
This ocean animal can sleep with only half its brain at a time.
What is a Dolphin?
Most people forget about 90% of their dreams within this short amount of time after waking up.
What is about 10 minutes?
Adults are typically recommended to get this many hours of sleep per night.
What is 7–9 hours?
Your brain temporarily does this to your muscles during REM sleep so you don’t act out dreams.
What is paralyze them?
The buildup of lost sleep over time is called this.
What is sleep debt?
Sleeping with half the brain at a time helps dolphins continue doing these two things.
What are swimming and breathing?
A famous sleep experiment had a student stay awake for about this many days.
What is 11 days?
This age group naturally tends to stay up later due to a shift in their circadian rhythm.
Who are teenagers?
Waking up but being unable to move for a few seconds or minutes is called this.
What is sleep paralysis?
Sleeping a lot on the weekend does this to sleep debt.
What is it helps a little but doesn’t fully fix it?
Some animals like horses and cows can sleep while standing up because their legs have special structures that lock their joints. These animals are often this type of animal that must quickly run from predators.
What are prey animals?
Scientists say that after about this many hours awake, your brain can perform about as poorly as someone who is legally drunk.
What is about 24 hours?
The body's internal clock that controls sleep and wake cycles.
What is the circadian rhythm?
Your body produces more of this hormone at night to signal that it is time to sleep.
What is melatonin?
Scientists have found that regularly getting too little sleep can increase the risk of weight gain because it disrupts hormones that control this feeling.
What is hunger?
This type of animal sleep—used by dolphins and some birds—allows one half of the brain to sleep while the other half stays awake.
What is unihemispheric sleep?
The average person has about this many separate dreams during a typical night of sleep.
What is 4–6 dreams?