jimmyd at cc.gatech.edu wrote:
> I want to know a few things about Neuron energy use.
> Please email me any ansewrs! Thanks in advance.
>> * Neurons get all their energy from glucose, right? (Kolb & Whishaw 1996, p
>> * The mitochondria turns glucose into ATP. Does the cell body have a storage
> of ATP, or does the mitochondria produce it as needed?
>> * How much glucose (turned into ATP) is needed to fire a neuron? If the firing
> rate of a neuron is 700 per second, what is the rate of glucose use?
>> * If neurons get all their energy from glucose, then what is the purpose of
> oxygen in the brain?
The same purpose it serves in an automobile engine.
> * This is my conception: The dendrites send a message to the soma indicating
> the change of firing rate. The soma takes energy from the bloodstream to
> raise the firing rate. This message is in the form of the chemical state
> inside the dendrites and soma. What is wrong with this conception?
There are other signal-encoding factors, that are as "tools" (the geometry of the
neural pathways (including tiny modifications to the neural geometry that
accumulate in accord with prior experience), neurotransmitters, hormones, and the
energy ambient in the external environment in which a nervous system's host
organism exists. Everything is integrated, and has a single goal of enabling the
host organism to climb the external energy gradient because that's where energy
(the nutrients upon which Life depends) exist most abundantly.
> The following questions assume the above conception is correct.
> * What happens if a neuron is heavily stimulated with messages from its
> dendrites, but there is not enough energy in the local bloodstream to increase
> the firing rate very much?
If this condition occurred, neural activations states would tend to become random
to the degree that it did, and the nervous system's information-processing
capacities would be decreased accordingly. But the evolutionary engineer has
handled this very circumstance nicely, and as any such condition shows itself,
system reconfiguration mechanisms are activated, and the nervous system guides the
effector activations of its host organism so that the organism will "move away
from" what has become a noxious environmental circumstance.
Sadly, this elegant stuff has an inherent flaw, but happily, this can be overcome
through an active guidance of the development of modifications to the neural
geometry (topology)... this's precisely what Science does when it discloses this
or that for folks' understanding... the understanding becomes encoded in
microscopic trophic (growth) modifications to the neural geometry, and,
subsequently, the modified neural geometry enables the nervous system to guide the
behavior of its host organism differently. Sound too-"complicated"? Look at it
this way: It's what we send our Children to school for... to have their neural
geometry altered... hopefully, for their benefit, and all of Society's, too.
> * What happens to the message after the rate changes (or doesn't in the case
> of low energy)?
Look around, and you'll see what happens all over the place... folks manifesting
"moving away from" behavior with respect to anything that's
relatively-unfamiliar... "familiar" stuff is the stuff that's come to be
strongly-encoded within the neural geometry. "Unfamiliar" stuff is just the
opposite. The former allows relatively-ordered neural activation. The latter
allows only relatively-disordered neural activation... activation that would be
correlated with the "out-of-energy" condition that you've brought up. My
discussion, above, pertains.
The "flaw" of which I spoke, above, has to do with the fact that, although what's
"unfamiliar" might very-well be something highly-beneficial to an organism, the
way that our nervous systems process information will, never-the-less, tend
strongly to guide us away from that which is merely "unfamiliar"... and we lose
out on what could have been our good fortune. ken collins