Your brain is weaker than your body

This post is also available in Dutch.

Your body, for the most part, is sturdily built. Your skin, muscles and bones easily recover from damage. Unfortunately, not your brain. Why does the brain recover poorly from injury?

Brain cells do not regenerate, so make sure to protect your head!
Image by Calspan Corporation via Wikimedia Commons (public domain).

Your body has to endure quite a lot during its everyday use, but it’s up to the task. If you fall off your bike, we can bandage your wounds, splint your bones, prescribe you some bedrest and your body is as good as new.

Alas, this does not apply to the brain. Brain cells do not heal by themselves, because they cannot multiply, unlike the many other types of cells in your body.

No cell division in the brain
The cells in our body multiply by dividing themselves. One cell becomes two, then four, eight, and sixteen, and so on and so forth. One part of the cell is essential in this process, which is called the ‘centriole’.

The centriole coordinates the (gentle) cleaving of the cell during multiplication. Nerve cells do not contain a centriole, and thus cannot divide. The only exception being the stem cells that exist in your brain, but they are few in number.

Protection from cancer
So, brain cells cannot multiply. Did evolution fail us in this regard? Not necessarily because anywhere cell division takes places, mistakes can also occur. These mistakes can cause cell multiplication to run awry.

This unrestricted multiplication is called cancer, and it is one of the leading causes for sickness and death. Not to say that brain cancer doesn’t exist, it absolutely does, but it’s relatively rare compared to cancer in other tissues thanks to the lack of cell multiplication in the brain.

Protection from pressure
Another potential reason is that the space for growth is restricted in the brain. Anybody who has been on the receiving end of a head-butt knows that the skull does not give way. These new brain cells would otherwise take up extra space, and could overcrowd the brain. The excessive pressure that would amass would be disastrous to brain function, that’s why depressurizing the brain is so urgent in treating brain injury.

Surviving cells take over
So when multiplication is not an option, the brain will try to mitigate any damage by having the surviving cells form new connections. By doing this, the remaining cells can pitch in for their fallen comrades.

Brain cell transplantation?
Unfortunately, the recovery of brain functions after injury is rather slow, and often the brain fails to make a complete recovery. This is why scientists are investigating the possibilities of transplanting healthy brain cells into damaged areas.

These transplanted cells could help with the process of recovery, but these new cells can only be useful when connected to the neural network, just like the heart is only useful when connected to the circulatory system. This can be quite a challenge.

Aside from this challenge, stem cell transplantation in the brain exists only in the realm of science fiction, for now. So for the time being, you would do well to cushion any and all incoming blows to your noggin, after all you only have one.

Click here for an open access scientific article discussing stem cell implantation to aid recovery from brain injury.

This blog was written by Pieter Schipper, who was a regular blogger at DondersWonders while working towards his PhD. Edited by Jeroen.

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