IUBio

newbie request

TONYJEFFS tonyjeffs at aol.com
Wed Jan 13 03:19:30 EST 1999


>Subject:	newbie request
>From:	Roberto2312 at hotmail.com (Roberto Colmegna)
>Date:	Sat, 09 Jan 1999 13:49:22 GMT
>
>I readed that a young man have a lot of sinapses
>which collapse during the firs year of life.
>
>Is know "why" these sinapses collapses?
>Is know what is the mechanis which conduce to this
>result?
>

The developing brain has to make billions of synaptic connections with a high
degree accuracy.  Rather than be 100% accurate in the first place, it is
presumably more efficient to produce twice as many neurons as necessary and
allow for some mistakes.  The ones that make correct connections survive.  The
ones that don't make the right connections die off.  So in the end we are left
with the correct number of brain cells and every synaptic connection is
correct.
This is called "programmed cell death"
The reason that the cells with the correct connections survive is to do with
something called "retrograde transfer".  Although the important information
goes outwards along the axon, there is also communication in the opposite
direction accross the synapse and back up the axon saying perhaps "message
received and acknowledged".  Without these retrograde messages, the synapse
will collapse, and if enough of the synapses of a single neuron collapse, the
neuron itself will die.

These aren't useful neurons that die. They are surplus to requirements.

........


Regards
Tony



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