17-3-24 #八级听力# 科普小文：The myth of sleep 别熬夜了，缺觉危害大

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The myth of sleep

Section 1:   

We're onlybeginning to understand why we sleep to begin with, but we do know it'sessential. Adults need 7 to 8 hours sleep at night, and adolescents need about10.    We grow sleepy due the signalsfrom our body telling our brain we are tired, and signals from the environmenttelling us it's dark outside. The rise in sleep inducing chemicals, likeadenosine and melatonin, send us into a light dose that grows deeper, makingour breathing and heart rate slow down and our muscles relax. This non REMsleep is when DNA is repaired and our bodiesreplenishthemselves forthe day ahead.

In the UnitedStates, it's estimated that 30% of adults and 66% of adolescents are regularlysleep-deprived.This isn't just a minor inconvenience. Staying awake can cause serious bodilyharm. When we lose sleep, learning, memory, mood, and reaction time areaffected. Sleeplessness may also cause inflammation, hallucinations, high bloodpressure, and it's even been linked to diabetes and obesity.

In 2014, adevoted soccer fan died after staying awake for 48hrs to watch the world cup.While hisuntimelydeath was due to a stroke, studies show thatchronically sleeping fewer than 6 hours a night increasing stroke risk by 4.5times, compared to those gettingconsistent7 to 8 hours of shut-eye.

Vocabulary:

Replenish,sleep-deprived, untimely, consistent

Section 2:

How can sleepdeprivation cause suchimmensesuffering? Scientists think the answerlieswiththeaccumulationof waste products in the brain. During ourwaking hours, our cells are busy using up our day's energy sources, which getbrokendowninto variousby-products, including adenosine. As adenosinebuildsup, it increases the urge to sleep, also known as sleep pressure. In fact,caffeine works by blocking adenosine receptor pathways. Other waste productsalso build up in the brain, and if they're not cleared away, they collectivelyoverloadthe brain and our thought to lead to the many negative symptoms of sleepdeprivation.

So what'shappening in our brain when we sleep, to prevent this? Scientists foundsomething called the Glymphatic System, a clean-up mechanism that removes thisbuild up and is much more active when we're asleep. It works by using cerebrospinalfluid to flush away toxic by-products that accumulate between cells. Lymphaticvessels, with serve as pathways for immune cells have recently been discoveredin the brain, and they may alsoplay a rolein clearing out the brain'sdaily waste products.

While scientistscontinue exploring therestorativemechanisms behind sleep, we can besure that sleeping intoslumberis a necessity, if we wanna maintain ourhealth and oursanity.

Vocabulary:

Immense,accumulation, overload,restorative, slumber, sanity