<p>Today I learned that a sudden jerk that you sometimes experience when you are just about to fall asleep due to a sense of free-fall or weightlessness is
called a <a href="http://en.wikipedia.org/wiki/Hypnic_jerk" rel="nofollow">hypnic jerk</a>.  </p>

<p>If, while sleeping, I roll over to the edge of the bed, I feel free-fall &amp; jerk up from sleep if I am about to topple down.<br>
But in case I am comfortably lying down in the middle of the bed with no chance of toppling down, how do I feel
weightlessness or free-fall when I am just about to fall asleep and jerk up, i.e. <strong>hypnic jerk</strong>?<br>
And not just on the bed; this is also experienced if you are sleeping on the ground where u cannot possibly physically fall.  </p>

<p>A bit more research in <a href="http://en.wikipedia.org/wiki/Falling_sensation" rel="nofollow">Falling sensation</a>  tells me its the ears &amp; the eyes that sense the free-fall.  </p>

<blockquote>
  <p>Sensation of falling can be induced when the eyes detect rapid
  apparent motion with respect to the environment.  </p>
</blockquote>

<p>How is this accounted for during sleep. Or is it something entirely different?</p>

CC BY-SA 3.0
2014-03-14T05:35:21.933Z
TIL the same thing...and also [the meaning of the acronym TIL](http://www.urbandictionary.com/define.php?term=til) ;)
Nick Stauner
<neuroscience><perception><sleep><motor>
How does the body experience free-fall during a hypnic jerk
KharoBangdo
# How does the body experience free-fall during a hypnic jerk

(Asked by: username_0 on 2014-03-14)

Today I learned that a sudden jerk that you sometimes experience when you are just about to fall asleep due to a sense of free-fall or weightlessness is
called a [hypnic jerk](http://en.wikipedia.org/wiki/Hypnic_jerk).

If, while sleeping, I roll over to the edge of the bed, I feel free-fall & jerk up from sleep if I am about to topple down.  
But in case I am comfortably lying down in the middle of the bed with no chance of toppling down, how do I feel
weightlessness or free-fall when I am just about to fall asleep and jerk up, i.e. **hypnic jerk**?  
And not just on the bed; this is also experienced if you are sleeping on the ground where u cannot possibly physically fall.

A bit more research in [Falling sensation](http://en.wikipedia.org/wiki/Falling_sensation) tells me its the ears & the eyes that sense the free-fall.

> Sensation of falling can be induced when the eyes detect rapid
> apparent motion with respect to the environment.

How is this accounted for during sleep. Or is it something entirely different?

**Tags:** neuroscience, perception, sleep, motor

> **Comments:**
> **username_1**: TIL the same thing...and also [the meaning of the acronym TIL](http://www.urbandictionary.com/define.php?term=til) ;)  

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## 0 answers

