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why does brain impact cause unconsciousness?

John M. Price ez001932 at othello.ucdavis.edu
Mon Sep 20 18:53:26 EST 1993


In article <27cvri$j0k at scunix2.harvard.edu> mlevin at husc8.harvard.edu (Michael Levin) writes:
>
>
>     Here are my thoughts on the subject of why brain impact causes
>unconsciousness, and if anyone has any ideas on this, please let me
>know. I am wondering: consider the lightest shock to the head (of a
>human, or a mammal in general) which is sufficient to cause
>unconsciousness of the temporary variety (being "knocked out"). Is
>this kind of shock really so traumatic to the brain as to cause it to
>relinquish control of the body and let it just lie there, or is this
>some sort of specific mechanism to deal with "stress"?  If it is the
>first (i.e., the brain is really injured by such a shock, and is
>unable to produce behaviors such as running away, until it recovers),
>what exactly is it that's wrong? I can't easily imagine any physical

Perhaps you should look at the old literature covering spreading
depression produced by the application of KCl to the exposed cortex.  This
seems mimic the response well.  Essentially, due to the sudden change in
membrane resting potential, K+ is supposed to be INSIDE the cell,
the cells go dormant for a time, and this depression spreads as th bolus
spreads through the cortex.

A mechanical perturbation can possibly cause enough of an upset, in enough
neurons to cause this imbalance, and this imbalance would be temporary. 
One must remember that the brain is sitting in a bag of fluid, and the
cortex, our seat of consciousness it seems would be the first to hit the
meninges/skull structure.

A much less intense, but similar phenomenon, can be seen if you get
a friend to hit you in the face.  At a high enough of an intensity of hit,
the dynamics (actually hydrolics) of the fluid suspended brain will be
enough to have the occipital cortex run into the occipital portion of the
skull/meningeal covering, and, viola, stars.  These stars are actually
phosphenes brought on by the "bruising" of the visual neurons.  Recall
that Johannes Muller gave us the concept of specific nerve energies
to account for this and similar phenomena.  That was in 1842.

jmp.


>
>Mike Levin



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