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Hello!<br>
The synaptic cleft (the actual 'gap' bit of the gap) is about 10 to 20 nm
across. (The synaptic 'gap' is the space between and the membranes both sides,
so about 20-30nm) A single vesicle full of neurotransmitter is about 50nm
in diameter, and fits at least 10,000 molecules of transmitter inside. It
has to really move its ass and if the gap were any bigger, we'd probably
all have been eaten waiting for the fight flight response to happen : )<br>
Diameter of neurons varies from 4 micron (granule cell) to 100 micron (motor
neuron in cord)<br>
(Diameter of neuron nucleus = 3 to 18 micron).<br>
The plasma membrane itself is about 5nm.<br>
Diameter of microtubule = 20-25 nm<br>
Diameter of neurofilament = 7-10 nm<br>
...But the density of neurons is an individual thing, and will vary from
area to area in each individual, and throughout that individual's lifetime.
An individual who regularly uses all bits of the brain a lot will really
pack 'em in, especially in bits like the hippocampus. Einstein's looked like
someone had tried to shove far too much macaroni into a very small pot.<br>
So if you want more elbow room for your bots, choose an extraordinarily stupid
subject, preferably with dendritic shrinkage already, big ventricles and
a small hippo. <br>
...Like, almost any celebrity? : )<br>
Otherwise, why not consider designs that are long and thin? Things that could
go UP axons ...Nanoworms. (Cue for a bad sci fi movie where nanoworms infest
everyone's brains and the hero invents the first intrathecal anthelmintic,
but cannot tell anybody because you cannot pronounce that over the telephone).<br>
...Please accept my apologies; I have been awake for a very long time. <br>
I'll stop now.<br>
Best,<br>
AR<br>
*********************<br>
Brett Paatsch wrote:<br>
<blockquote type="cite" cite="mid018301c49b2a$8214f600$ec202dcb@homepc">
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<div><font face="Arial" size="2">Hi Alex,</font></div>
<div> </div>
<div><font face="Arial" size="2">Do you know how much space is between
axons, dendrites, synapses on neurons in the most densely packed part of
the brain? ie how tight do neurons pack at</font></div>
<div><font face="Arial" size="2">their tightest and most dense?</font></div>
<div> </div>
<div><font face="Arial" size="2">Reason I ask is that I think that is an
important design scale limit on any servicing/repairing nanobots that might
want to get between them. </font></div>
<div> </div>
<div><font face="Arial" size="2">In actual fact I suspect that to try and
get a nanobot into the extracellular spaces between neurons may be impossible,
because the space may be</font></div>
<div><font face="Arial" size="2">as little as 10s of nanometres in places
(and the space map would be different for every brain - more different than
variations in vasculature) and</font></div>
<div><font face="Arial" size="2">no nanobot with a payload worth a damn
could get much smaller than a half a micron I'd guessimate.</font></div>
<div> </div>
<div><font face="Arial" size="2">Cheers,</font></div>
<div><font face="Arial" size="2">Brett</font></div>
<div> </div>
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