Why is it when youre falling asleep?

This is a normal part of falling asleep - indeed, our brain may well think we are literally "falling" into sleep.

Here's a good summary of the phenomenon...

Do you ever wake up suddenly to a falling sensation and a strong muscle twitch just after you have fallen asleep?

This strange falling sensation and muscle twitch is known as a hypnagogic myoclonic twitch or “Hypnic jerk” If this has happened to you on more than one occasion, don’t worry, you are not alone. Close to 70 percent of all people experience this phenomenon just after nodding off, according to a recent study at the Mayo Clinic.

Most experts agree that this is a natural part of the sleeping process, much like slower breathing and a reduced heartbeat. The occurance is well known and has been well documented. However, experts are still not completely sure why the body does this.

The general consensus among researchers is that, as your muscles begin to slack and go into a restful state just as you are falling asleep; your brain senses these relaxation signals and misinterprets them, thinking you are falling down. The brain then sends signals to the muscles in your arms and legs in an attempt to jerk you back upright. This misinterpretation that takes place in your brain may also be responsible for the “falling” dreams that accompany the falling sensation. These “dreams” are not really normal dreams, as they are not produced from R.E.M sleep, but rather more like a daydream or hallucination in response to the body’s sensations.

SleepingWhile this phenomenon happens to most everyone, studies have recently begun to link occurrences of “Hypnic jerks” to sleep anxiety, fatigue, and discomfort. People who are having trouble sleeping or can’t get comfortable in bed appear to experience the sensation more often throughout the night. It is especially more common with people who are trying to fight falling asleep or have deprived themselves of sleep for more than 24 hours.

Researchers believe that the lack of sleep from sleep anxiety or sleep deprivation confuses the muscles and the brain. The muscles continually attempt to relax and shut down for rest, while your brain remains awake creating continued “misinterpretations” of falling or loss of balance.

Scientists and researchers continue to study sleep twitching and jerking in a small capacity, but state that the sensation is completely normal for our bodies and is of little medical significance. Our bodies go through several procedures of shutting down and preparing for an extended period of rest. “Hypnic jerking” is just one of them. It doesn’t appear to cause damage to body and poses no danger to our physical wellbeing. That may be true, but it could pose a significant danger to my bed when I mess my pants next time I wake up thinking I just fell off of a building.

Because your unconscious mind is reminding you that you are not at a place where you should be asleep....or with other words: deep down inside is this alarm system that tries to keep you awake in school or any other place......

to make a very long answer short-it has to do with the dumping of certain cations into your blood which excites the muscles as you're falling asleep-used to have it happen to me all the time at school lol

Your brain is telling your body that u don't want to sleep..Nerves could be settling also...

good question.