The day is winding down and it’s getting close to bedtime. Your eyes get heavy and you just can’t stop yawning. Your circadian rhythm, also known as your biological clock, is telling your body that it’s time to sleep.
We typically sleep in 24-hour cycles triggered by sunlight. Once the sun goes down and you drift off to sleep, your brain begins rotating through a series of neurological phases. This is the time when your daily experiences convert into long-term memories.
During the first stage of sleep, your body begins to relax. Your heart rate and breathing slow and your muscles may twitch.
As you relax further into sleep, your eyes stop moving and your body temperature drops. Your muscles grow limp.
“Stage three is what we like to call ‘deep sleep,’” Dr. Levinson says. “This stage of sleep is the most refreshing and what causes you to wake up feeling renewed and ready to take on the day.” Waking up is hardest during this stage, as your body is completely relaxed.
During the REM (rapid eye movement) stage, your eyes move quickly behind your eyelids and your heart rate begins to raise. You do most of your dreaming during this stage. Dr. Levinson says, “The reason we don’t act out our dreams is because the brain stem releases a chemical called GABA during REM sleep that temporarily restricts movement.”
REM sleep lasts about 10 minutes before cycling back to stage one and so on. We typically rotate through these stages a few times throughout the night. “Practicing good sleep hygiene will help establish a strong circadian rhythm and allow you to sleep better during the night,” says Dr. Levinson.
Talk to your doctor if you experience trouble sleeping for two or more weeks.