You'd understand what I'm talking about when I say that it's the most relaxing time of the day. There's no better feeling than putting your head on your fluffy pillow, resting your eyes a little bit, checking your phone, watching something on Netflix, and relieving your tiredness. Sleep indeed is one of the most beautiful parts of living, and eating would be the runner-up.
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However, even sleeping can be trouble for humans. Sometimes you don't want to go to sleep because you have the same nightmare every night, you have the boogeyman under your bed, or you have sleep apnea that sleeping makes you even more tired than working for hours.
But these aren't the only concerns we have about sleeping. There are more interesting things than having the same nightmare, more real things than the boogeyman and, well, more mysterious things than sleep apnea.
Here are the basic scientific explanations for the things we experience during sleep.
1. Sleep Paralysis
Have you ever had a moment where you can't move, speak or scream while you're falling asleep or waking up? Sometimes when you're experiencing this, you might see a shadow in the corner of your room, you feel someone's breath on your ear or someone's hands on your throat. If so, for sure you got scared, especially when it happened for the first time, but there's nothing to be scared of.
It actually has a simple, very simple explanation. If the sleep paralysis happens when you're waking up, it's called hypnopompic or postdormital sleep paralysis and if it happens when you're falling asleep, it's called hypnagogic or predormital sleep paralysis.
When you're falling asleep, your body slowly relaxes, you become less aware, and your body becomes less responsive to your brain signals. However, if you become aware or remain awake while you're falling asleep and while your body starts to relax, you'd realize that you can't speak or move.
It's different when you're waking up. Sleep has two stages; NREM sleep and REM sleep. NREM also has three different stages; the first stage is the transition from being awake to falling asleep. Heartbeats and breathing begin to slow. This stage lasts usually for 5-10 minutes and it constitutes 5% of sleep time.
The second stage lasts usually for 10 to 25 minutes, and it's considered a period of light sleep. Heart rate slows, muscles relax, eye movements stop. It constitutes 55% of total sleep time.
The third stage of the NREM sleep, "slow-wave," "delta," or "deep" sleep is the stage of sleep that lasts for 20 to 40 minutes and needed for an individual to feel refreshed in the morning. Heart rate and breathing become the lowest level, blood pressure falls and body temperature drops. It's the most difficult stage of sleep to wake up and represents 15% of total sleep time.
After about 90 minutes into sleeping, a person enters REM sleep. This is the stage where a person's eyes move from side to side beneath closed eyelids. At this stage, most of the dreaming occurs. While heartbeats increase and blood pressure rise, arms and legs become unable to move, due to the reason of not acting out the dreams we have. Adults spend 20-25% of their total sleep time in REM sleep.
If you regain your consciousness and start to wake up before your REM sleep cycle finishes, you'll be unable to move or speak since your muscles are turned off to avoid acting out your dreams.
As you can see, it's not something that you should be scared of, just stay calm when it happens, and it'll go away in seconds.
2. Hypnic Jerk
Sometimes when you're sleeping like an angel or like a gorgoneion, you wake up abruptly feeling like you're falling down. At the same time, you see yourself falling from a cliff, from the 17th floor or anywhere and you wake up jumping.
Hypnic jerks, also known as sleep starts, mostly happens when you're falling asleep and it's caused by a form of involuntary muscle twitch called myoclonus, hiccups are also a form of myoclonus.
There's no exact cause for hypnic jerks, but its possible causes include anxiety, caffeine, nicotine, stress, and sleep deprivation.
This is one of the scariest things that can happen when you're sleeping, except for the ghost of the old lady that used to live in your apartment and died horribly. Hehe, just kidding.
Sleepwalking basically is a behavior disorder occurs during sleep and performing walking or other behaviors while sleeping. Behaviors of people who sleepwalk may include, sitting up in their beds, walking around the house, leaving the house, driving, and sometimes even eating.
Sleepwalking usually occurs in the first hours of sleep. There's not an exact cause of sleepwalking but it's mostly seen in people with a sleepwalking behavior in the family history. Sleep deprivation, stress, anxiety, and certain types of medication can also cause sleepwalking.
4. Lucid Dreaming
During a lucid dream, the person is aware that s/he is dreaming. The dreamer may gain control of his or her dream, and lead the characters, environment, and the narrative in the way s/he wants.
Lucid dreaming has been studied from ancient times until today, and people have been fascinated by it. Lucid dreaming usually happens during REM sleep. Around 55% of people experience a lucid dream once or more in their lifetime while some other people train themselves to dream lucidly.
So, let's say a killer is chasing you in a dream and you're running away from him, and then you say to yourself "Wait for a second, why am I running from a killer in the middle of the night in an abandoned hospital? I didn't even come here, so, this is a dream. Let me just fly away from this jerk." This is exactly what happens when you're lucid dreaming.
5. False Awakening
Say, you're having a dream, a scary one. And you finally wake up, the monsters are gone. So you take a deep breath, go to the bathroom, wash your face, and what the ACTUAL HELL?! The monster is right behind you? What? Was it all real? Oh dear God, run! And everything starts from the beginning. Ah man, you have to run from the monster again.
And then you wake up, this time for real. Or maybe not? Keep on trying until you wake up to real life.
A false awakening is actually a thing that can happen to anyone. Sometimes it can be a dream within a dream, or maybe a dream within a dream within a dream, like a Russian nested doll. It can be caused by sleep apnea, insomnia, anxiety, mixed brain states or other causes.