Why our body jerks while we are falling asleep?
As our body is ready to fall asleep, sudden twitches escape out of our brains, causing jerks to our legs and arms. They amuse some people while others feel really embarrassed. Technically, these are the hypnic jerks. The exact cause is not realized yet, but according to some studies, they are the side effects of a hidden battle to in the brain that happens during sleep to take control on the cusp between dreams and wakefulness.
Sleeping takes the human body in a state of paralysis. Even at the times of the most vivid dreams, our muscles stay still and relaxed, displaying little sign of our internal excitement. Events happening in the outside world goes into the ignoring mode. Various experiments have proven that even if you slept with your eyes taped open and flashed a light in your eyes, it is unlikely that it will affect your dreams.
However, the door between outside world and your dreams is not completely closed. Usually, two kinds of movements escape the dreaming brain, and both of them have a different story to tell.
The general movements we make while we sleep are the fast eye movements. When we nightmare, eyes move in accordance to what we dream about. If let us say, in our dream, we are watching a game of tennis. Then our eyes will move from left to right rapidly. These actions in the dream space escape from the general sleep paralysis and drip into the actual world. If a person’s eyes are moving while they sleep, it is the strongest signal that they are dreaming.
Hypnic bumps are not like it. They are very much general in children when our dreams are very usual, and they do not show what is happening in the dream. If you dream of driving bike you don’t shake your legs in a cyclic manner. Instead, hypnic bumps seem to be a symbol that the motor structure can still wield some control over the body as sleep paralysis take you over. Apart from having a single “sleep no sleep” toggle in mind for controlling the sleep (i.e. ON at night, OFF at daytime), we have two different systems that balance each other. Here, each has to take the control from the other.
Deep down below in mind, below the cortex (the most developed part of the brain) a nerve cell network called the reticular activating system is present. This is snuggled among the chunks of the mind that control the fundamental physiological processes, like breathing. We are awake when the reticular activating system is in full force.
Contrasting this scheme is the ventrolateral preoptic nucleus. ‘Ventrolateral’ means it is on the base and near the edge in the head. ‘Preoptic’ means, it is only at the point where the nerves cross the eyes. We name it the VLPO. The VLPO brings drowsiness, and its setting near the optic nerve is apparently so that it can accumulate knowledge around the commencement and end of daylight time, and so encourage our sleep cycles.
As your mind becomes usual to its regular task of understanding the external world and begins generating fun for its own, the struggle between the reticular activating system and VLPO goes in the latter’s favour. What happens then is not defined very well, but it looks like the story is that the struggle for governance of the motor system is not over yet. When sleep paralysis begins, the remaining daytime energy sparks and erupts out in apparently random movements. In other words, hypnic jerks are only the last bursts of the remaining daytime energy.
Some people report that hypnic jerks happen when they dream of falling or tripping up. It is a phenomenon referred to as dream incorporation. In it, an external process, such as an alarm clock, builds up into your dreams. It shows our mind’s capacity to generate incredibly plausible stories. The planning and foresight areas of the brain are repressed while dreaming. This allows the mind to react way more creatively to wherever it wanders.
While hypnic jerks are escaping during the struggle between sleep and wake, the mind is busy undergoing its transition. While sleep draws a veil over the external world as we fall asleep, hypnic jerks are close enough to home. They are the movements of our bodies attracting the attention of sleeping consciousness.
So, there is an unusual pleasing symmetry between the two different kinds of movements we make while our body in sleeping phase. While rapid eye movements refer to the traces of dreams that stays with us in the awake world, hypnic jerks seem to be the wild traces of one’s awake world that intrudes in the dream world.