Page 164 - The Miracle in the Cell Membrane

The Miracle in the Cell Membrane

Synapse Paths
The human nerv ous sys tem is a com plex net work con sist -
ing of bil lions of nerve cells that estab lish com mu ni ca tion
among them selves and other cells in the body by means of
syn ap ses—small parts of the nerve cells that approach one
anoth er very close ly but never actu al ly touch. Since they
never come into con tact with one anoth er, sig nals do not pass
from one cell to anoth er direct ly, but are car ried through the
gaps by chem i cal neu ro trans mit ters.
When a sig nal reach es the trans mit ting cell, that cell caus -
es some neu ro trans mit ters to be secret ed into the extra cel lu -
lar space. At this the neu ro trans mit ter mol e cu les dif fuse in
this space—pass ing direct ly into a less dense envi ron ment—
and attach to the recep tor pro tein mol e cu les on the sec ond
cell. Since there are many kinds of neu ro trans mit ter and
recep tor mol e cu les, the syn apse can cross very quick ly (in
1/1000th of a sec ond) or rath er slow ly (1/100th of a sec ond).
Chemical agents set the sec ond cell in action, or else halt it.
Therefore, syn ap ses serve to alter the infor ma tion in the nerv -
ous sys tem or set it in motion. Because of these prop er ties, the
func tion of syn ap ses in the brain is con nect ed with learn ing
and mem o ry.
As neu rons trans mit mes sa ges by means of the syn ap ses,
they exchange chem i cal sig nals. The nerve cells in your brain
have 100 tril lion con nec tions, where there is a con stant and
enor mous molec u lar traf fic. The elec tri cal ly-charged chem i -
cals known as ions and large and small vari e ties of pro teins
tell this traf fic when to flow, and when to halt.

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