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  • Every night, almost everyone on the planet enters into a state of unconsciousness and paralysis.

  • But what is really happening inside the body when we drift off?

  • And what's the impact if we don't get enough sleep?

  • Sleep is regulated by your circadian rhythm, or body clock, located in the brain.

  • The body clock responds to light cues,

  • ramping up production of the hormone melatonin at night and switching it off when it senses light.

  • There are four stages of sleep that the body experiences in cycles throughout the night.

  • On a good night, we cycle through these stages four or five times.

  • Stages one and two are light sleep.

  • This is a transition from being awake to falling asleep.

  • Heart rate and breathing begin to slow,

  • body temperature falls, and muscles may twitch.

  • Stage three is sometimes referred to as delta sleep

  • because of the slow delta brainwaves that are released during this stage.

  • This is the first stage of deep sleep,

  • where our cells produce the most growth hormone to service bones and muscles, allowing the body to repair itself.

  • Stage four is where we begin to dream.

  • The body creates chemicals that render it temporarily paralyzed so that we do not act out our dreams.

  • In this stage, the brain is extremely active and our eyes, although closed, dart back and forth as if we were awake.

  • Humans roughly spend 1/3 of their lives asleep.

  • Modern lifestyles, stress, and the proliferation of technology mean that people are sleeping far less today than they were a century ago.

  • Sleeping less than seven hours per day is associated with an increased risk of developing chronic conditions, which could reduce life expectancy.

  • So for a healthier, longer life, get some shuteye.

Every night, almost everyone on the planet enters into a state of unconsciousness and paralysis.

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B1 UK sleep body stage delta hormone awake

What happens when we sleep? | The Economist

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    Jerry Liu posted on 2019/04/02
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