Why people become unconscious after they hit something with their head?
In: Biology
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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