Improving medical students

Understand the Mechanics of Sleep

Posted by medliorator on January 7, 2008

  • Sleep occurs in cycles of around 90-110 minutes each. Most people normally go through 5 cycles during the night (7.5-8.5 hours). If you sleep for 6 hours you’re likely to be on a 4-cycle diet.
  • Each cycle includes 5 different stages occurring in particular order.
    1. Drowsy sleep – transition period from wakefulness to sleep… awakened easily. Your eyes move slowly and muscle activity slows. You start losing conscious awareness of the external environment. It’s this stage when you occasionally may experience sudden twitches and hypnic jerks from the sensation of falling or striking (don’t worry, these are normal).
    2. Light sleep – your body is relaxed and prepares to enter deep sleep… lasts longer than other stages – you spend 45-50% of your sleep in Stage 2.
    3. Deep sleep
    4. Deep sleep – characterized by maximum brain and muscle relaxation with stage 4 being effectively a deeper version of stage 3. Stage 3 is when you may experience night terrors, sleepwalking, and sleep-talking occur. [Those awakened] during deep sleep often feel groggy and disoriented for several minutes. In deep sleep, there is no eye movement or muscle activity and the body is still. You usually [get] less deep each cycle, so that most of your deep, stage 4 sleep occurs in the first half of the night.
    5. REM sleep – This stage is very different from all other stages because in REM sleep brain wave activity is similar to an awakened state. At this stage body experiences periodic eyelid fluttering, muscle paralysis, irregular breathing. Your heart rate increases and blood pressure rises. This results in intense dreaming, which occurs mostly at REM sleep stage. The end of REM stage is an ideal time for waking up.
  • Stages go in the following order to form a full cycle: 1-2-3-4-3-2-1-REM
  • Duration of each stage may vary from 5 to 15 minutes. REM stage lasts for 10 minutes ending first cycle, with each recurring REM stage increasing in duration, and the final one lasting an hour. Total cycle ends up taking around 90-110 minutes. First cycles are usually shorter (closer to 90 minutes).
  • Drugs such as alcohol and sleeping pills can suppress certain stages of sleep. Even though you’ll sleep longer, such sleep may not fulfill its physiological functions completely.
  • The best time to wake up is at the end of the cycle. You should pay more attention to your state when you wake up to try and identify what stage you are awakening from.
  • If alarm wakes [interrupts] your dream, [it’s] very likely you’re in a REM stage or stage 1, good times to wake up.
  • If you feel extremely disoriented when trying to wake, you’re waking from stages 3 or 4, wrong times to wake up. Take another 30 minutes of sleep.
  • Write down how long you sleep each day and try to adjust your sleep duration so you wake up at the end of the cycle. Again, this can be done by paying closer attention to your state and your feelings at wake up time.

Understand Sleep Mechanics []


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