"1234" <123412 at 101.com> wrote in message
news:cpt14f01b03 at news4.newsguy.com...
>> Explain "diffusion" to a layman please?
Take a glass of water. Drop a drop of food coloring into the water. As you
watch, the food coloring slowly spreads until there is no part of the glass
of water that's any more colored than any other part. That process is
If you want to imagine this on a molecular level picture a tray with some
white ping pong balls on it. Take a handful of colored ping pong balls and
put it in the center of the tray. Now start gently shaking the tray around,
and you'll see as the ping pong balls start moving around the colored ping
pong balls eventually will end up all over, instead of clumped together. In
real life molecules move as a function of heat - the hotter the system, the
faster the molecules move. In the random movement of molecules (this is
what is called Brownian motion, BTW), molecules of different types and at
different concentrations tend over time to become randomly distributed at
Same thing with the neurotransmitter. It spreads from areas of higher
concentration to areas of lower concentration until it reaches equilibrium.
This process is constrained by the cellular walls of the involved neurons
and surrounding cells to a certain extent, because molecules don't diffuse
at the same rate across them (insert vague hand waving in place of an
explanation of cell wall transport issues), but the essential mechanism is
the same as in the food coloring example.