WEBVTT - Why Do We Sleep?

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<v Speaker 1>Welcome to brain Stuff from How Stuff Works. Hey, I'm

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<v Speaker 1>Christian Seger, and this is brain Stuff. Here's a quote

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<v Speaker 1>for you from American lightbulb man Thomas Edison. He said

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<v Speaker 1>sleep is a criminal waste of time, inherited from our

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<v Speaker 1>cave days. Well, like Edison, we hear at brain Stuff

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<v Speaker 1>hate sleep. That's why we wanted to do this episode

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<v Speaker 1>to figure out why we have to do it. Normal

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<v Speaker 1>people spend thirty of their lives asleep, and most are

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<v Speaker 1>either like us and wish that they didn't have to

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<v Speaker 1>sleep so they could get more done, or they just

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<v Speaker 1>want to get a RESTful, uninterrupted night without waking up.

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<v Speaker 1>Studies actually show that six adults claim to have problems

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<v Speaker 1>sleeping at least a few nights a week. And here's

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<v Speaker 1>the thing. Everyone's got to sleep. Yet we still don't

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<v Speaker 1>know exactly why, but we're gonna try to do our

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<v Speaker 1>best to crack that case today. That's right, let's review

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<v Speaker 1>some theory reason for why we sleep, What happens when

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<v Speaker 1>we sleep, and what happens when we don't. Even though

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<v Speaker 1>we don't know why we sleep, there's all kinds of

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<v Speaker 1>educated speculation. The most prevalent is that sleep gives our

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<v Speaker 1>brain a chance to organize and process information, possibly through dreams. Basically,

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<v Speaker 1>our brain takes all the sensory stimuli we received while

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<v Speaker 1>we're awake and decides what to keep and where to

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<v Speaker 1>file it. Everything else gets trashed. It's even possible that

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<v Speaker 1>our ability to learn tasks actually benefits from quote sleeping

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<v Speaker 1>on it as a process is better understood after our

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<v Speaker 1>brain reviews and catalogs it. While most agree with this

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<v Speaker 1>memory consolidation theory, it's tough to pin down since we

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<v Speaker 1>all sleep so differently. And here's another theory. Sleep gives

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<v Speaker 1>our bodies time to rest and repair. Or how about

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<v Speaker 1>sleep lowers our energy consumption so we conserve the meals

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<v Speaker 1>we eat. Other theories delve into the biochemical mechanism of

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<v Speaker 1>the brain. In a series of experiments on mice, showed

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<v Speaker 1>that cerebral spinal fluid was pumped around their brains while

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<v Speaker 1>they slept, expelling waste like molecular detritus and toxic proteins

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<v Speaker 1>into their livers for breaking down. So do we sleep

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<v Speaker 1>just to flush the toilet on our cerebral commodes? Well,

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<v Speaker 1>Other sleep researchers were skeptical of the study that I

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<v Speaker 1>just mentioned pointing out that there are some big differences

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<v Speaker 1>between a mouse's brain and humans. So while the answer

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<v Speaker 1>to why we sleep isn't written in stone, we all

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<v Speaker 1>know that when we sleep, both our mind and our

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<v Speaker 1>body feel refreshed. We at least know what's happening when

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<v Speaker 1>we sleep right well, most of us need between seven

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<v Speaker 1>to nine hours of sleep at night, but that changes

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<v Speaker 1>during different periods of life. For example, a newborn baby

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<v Speaker 1>might sleep twenty hours a day, but by the time

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<v Speaker 1>they're three months old, they recognize the circadian rhythm of

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<v Speaker 1>sleeping at night and waking up in the morning. And

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<v Speaker 1>when you're older, like senior citizen, older can probably get

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<v Speaker 1>by on only six or seven hours a night. Regardless

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<v Speaker 1>of how long you're a sleep, you must experience both

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<v Speaker 1>R e M and non r e M stages to

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<v Speaker 1>sleep well. That's rapid eye movement, not the band R

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<v Speaker 1>E M from Athens, Georgia. A normal person spends of

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<v Speaker 1>their sleep in R e M, with each session lasting

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<v Speaker 1>between five and thirty minutes, and during this time our

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<v Speaker 1>brain speeds up, our eyes and face might twitch in

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<v Speaker 1>R e M because we're dreaming. We need around ninety

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<v Speaker 1>minutes to fulfill a complete cycle of R E M

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<v Speaker 1>N non R E M sleep, and researchers think this

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<v Speaker 1>cycle ties sleep back to our ability to process tasks

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<v Speaker 1>and memories. Recordings show that many of the same neurons

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<v Speaker 1>that fire when we're learning are reactivated during R E M,

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<v Speaker 1>consolidating the patterns into permanently wired connections. But don't sleep

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<v Speaker 1>too much more than eight hours can lead to depression

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<v Speaker 1>or even Parkinson's and heart disease. Of course, if we

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<v Speaker 1>don't sleep, that's a whole other mess of problems. Rats

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<v Speaker 1>will actually drop dead if they go more than three

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<v Speaker 1>weeks without sleep. Us humans we get lethargic, cranky, and

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<v Speaker 1>foggy headed at first, almost like we're intoxicated. We might

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<v Speaker 1>even nod off into micro sleep for a few seconds,

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<v Speaker 1>and this is what happens after one or two nights

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<v Speaker 1>without sleep. By day three, we start hallucinating and lose

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<v Speaker 1>the ability to recognize reality. That's if you're really pushing

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<v Speaker 1>the boundaries of sleep. Simply failing to get enough sleep

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<v Speaker 1>is connected to obesity, high blood pressure, a weakened immune system,

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<v Speaker 1>heart disease, cancer, and diabetes. And it's no big revelation

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<v Speaker 1>that lots of us don't get enough sleep. We might

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<v Speaker 1>try to get by on caffeine or nicotine, and alcohol

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<v Speaker 1>is a good sedative, but it doesn't actually provide the

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<v Speaker 1>sleep we need for neural processing. So, in the words

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<v Speaker 1>of the immortal poet Chris Ludicrous Bridges is, if you're tired,

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<v Speaker 1>be quiet and go to sleep. Check out the brainstuff

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<v Speaker 1>channel on YouTube, and for more on this and thousands

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<v Speaker 1>of other topics, visit how stuff works dot com.