Why We Suddenly Jolt Awake When We’re Falling Asleep

Everyone has likely experienced a hypnic jerk or sleep start at some point in their lifetime. It’s that moment where you jolt awake because of the sudden movement of your muscles. They can range from small twitches to convulsions, causing you to sit straight up in your bed. Even though we normally fall asleep again shortly after, it does leave us wondering how this could have happened.

Bright Side has studied the topic for you and wants to shed some light on why we suddenly jump up from our bed right before drifting off to sleep.

Normally, your brain paralyzes you during sleep.

Perhaps it’s first important to understand why we don’t move during our sleep normally. Because even when we have the most vivid dreams, we just wake up in exactly the same spot as where we dose off. This happens because there are chemicals released in the brain that switch off the cells that allow muscles to be active. So even though your brain is actively working, the muscles in your body remain paralyzed.

This is done by transitioning between awareness and sleepiness.

To understand why sometimes we don’t seem to be perfectly paralyzed, let us take a look at what is actually happening in the brain. There are 2 main systems that control regular life. The first one is called the reticular activating system and it’s the part that governs basic physiological processes, like breathing. When this is in full force, we feel alert and restless — we’re awake. Opposing this system is the ventrolateral preoptic nucleus, which drives sleepiness. This part of the brain releases the chemicals that switch off your ability to move your muscles. Now when you go to sleep, your brain switches from the state of awareness to the state of sleepiness. But this does not work like an “on-off” switch. In fact, you can think of it more as a sliding mechanism that transitions from one to the other.

But sometimes your brain is battling for control between the real world and the dream world.

This transition doesn’t always run smoothly. When there’s a glitch, your brain is battling for control between the real world and the dream world. So when you dream of kicking a football, for instance, this could suddenly translate into you actually giving a kick to your bed partner. It doesn’t always wake you up, but when the movement is intense enough, it will.

This could be related to our primate reflex.

One popular idea as to why we have those hypnic jerks or sleep jumps is that it’s a byproduct of our evolution. It could be an ancient primate reflex that warns you against relaxing muscles when you’re sleeping up high in trees. The brain essentially misinterprets the relaxation as a sign that the sleeping primate is falling out of a tree and causes the muscles to quickly react as a warning system.

Hypnic jerks are normal until they start to cause anxiety.

Hypnic jerks are completely normal and nothing to be concerned about. But people can get fixated on them, which can cause anxiety. This, again, can lead to annoyance when it happens more often — especially for your bed partner. This increased anxiety and sleeplessness can lead to more hypnic jerks, resulting in a positive feedback loop. If this is happening to you, it might be better to consult a sleep specialist to see what you can do about it.

Have you ever experienced a hypnic jerk yourself? How did you handle the situation?