Why people become unconscious after they hit something with their head?
In: Biology
Yor brain is surprisingly delicate. When you hit your head hard you shake your brain in your skull(if you want a larger example of how this works, think about when you slam on the breaks while driving, you get thrown forward). When your brain slams into the side/front/back of your skull hard enough it can cause your brain to get injured. When that injury happens your body might skip a beat before it recovers(very few blows to the head actually result in you going fully unconscious for more than a split second, and in fact if you fall unconscious from hitting your head there is a significant risk that you are about to die or at least suffer long term mental damage)
Just to clarify: What we often see on TV, person gets whacked, they fall unconscious, stay out for as long is convenient for the script, then they wake up with little lasting effect…this isn’t the way it works in real life.
Even boxers, trained in taking a punch, and often being interviewed shortly after being knocked out, end up in the hospital. Some boxing federations now require the knocked out boxer to be boarded and examined in a hospital.
We don’t really know. There are four main ideas about the mechanism of consciousness alteration in mild traumatic brain injury (concussion). Here is a short description of each:
* Electrical and chemical activity in part of our brain stem (the reticular activating system) is necessary for consciousness. Maybe when we hit our heads, we lose consciousness by disrupting the activity in this region.
* We have another part of the brain that can inhibit consciousness when activated (in non-ELI5 technical jargon: inhibitory cholinergic projections from the laterodorsal tegmental nucleus and pedunculopontine nucleus). Maybe when we hit our heads, we lose consciousness by activating this system at the wrong time (it is usually activated during certain phases of sleep).
* It is also argued that physical shearing forces can temporarily separate brain cells from communicating with each other. (We don’t know how consciousness works, but it is safe to say that temporarily disconnecting many brain cells in large enough numbers would lead to changes in consciousness). Maybe hitting our heads can temporarily block brain cell signaling in this way.
* We also know that electrical activity has to be organized in order for you to be conscious. (More electrical activity does not mean more consciousness, sometimes the opposite). Sometimes too much random electrical activity can lead to a loss of consciousness (like in some forms of epilepsy), and it’s possible that hitting our head can shake things up in a way that leads to too much disorganized electrical and chemical activity.
If you want more technical terms, here is a quote from a paper: “Several plausible hypothetical mechanisms have been proposed for the alteration of consciousness that occurs with mTBI. These include the reticular, pontine-cholinergic system, centripetal, and convulsive hypotheses. … In summary, none of the individual hypotheses currently available explain all the findings seen with mTBI. Given the often complimentary strengths and weakness of the four hypotheses discussed above, it seems likely that the mechanisms of altered consciousness after TBI may be due to a combination of processes.” ([source](https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2923650/)).
tldr: it is not understood how we lose consciousness after hitting our heads, but it’s probably a combination of several things that are known to be able to lead to disrupted brain cell activity patterns.
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