I stacked my bike and split my head right open. About three weeks later the scab falls off and the skin is sealed over, like magic! How does it all work? How does the brain know that part of the body is injured and needs repair, or does the brain know at all? What kind of signals between brain/cells/body are involved.

Sorry it's probably a basic question for a biologist, but I come from a different field and have always wondered about this amazing process. It's also a very hard topic to google about, because most results are about spiritual healing, crystals, prayer and a lot of pseudoscience rubbish.


Healing in the body is normally independent of the brain. Following an injury, a process of inflammation attracts lots of cells to the site of the injury (including platelets, white blood cells, clotting factors). There's also vasoconstriction (tightening of your blood vessels) to reduce blood loss from the injury site. Your skin cells continue to divide rapidly until new skin replaces the damaged one which later falls off. This is a highly simplified version of the process but hope it makes sense. So in summary, healing takes place by cell division (also known as mitosis).

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    $\begingroup$ Amongst other things, contact inhibition is also important to stop the cells from over-proliferating. $\endgroup$ – nico Jun 11 '13 at 15:03
  • $\begingroup$ Hm, do you think that is also possible explanation of the kind of placebo case with soldiers whose injuries healed more slowly if was stressed? How brain tightens the blood vessels? $\endgroup$ – Probably Aug 29 '15 at 4:52
  • $\begingroup$ aha, dana.org/Publications/ReportDetails.aspx?id=44313 says something quite different $\endgroup$ – Probably Aug 29 '15 at 4:54

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