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Part 4
Listen and answer questions 1 – 10.
Write NO MORE THAN ONE WORD for each answer.
Complete the notes below.

The Science of Sleep

Basic Facts About Sleep
  • Average adult needs around hours of sleep per night.
  • Sleep is an active process — the brain does important work during sleep.
  • Each sleep cycle lasts approximately minutes.
Types of Sleep
  • Two main types: non-REM sleep and sleep.
  • Dreaming mainly happens during the second type.
  • Deepest non-REM stage = slow-wave sleep: repairs muscles and strengthens the system.
What Controls Sleep
  • The body's internal clock is called the rhythm.
  • In darkness, the brain produces , which causes sleepiness.
  • Sleep pressure is caused by a chemical called building up in the brain.
Effects of Poor Sleep
  • Short-term: reduced concentration and slower times.
  • Long-term risks include heart disease, obesity, and type two diabetes.
  • Around percent of adults experience insomnia at some point.
Tips for Better Sleep (Sleep Hygiene)
  • Keep a regular sleep schedule every day, including .
  • Avoid screens at least one hour before bed — blue light reduces melatonin.
  • Keep your bedroom cool and dark.