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Brain & Computer--How
Biological Neurons Work
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 he neuron
is a functional unit of the body's nervous system that transmits electro-chemical impulses through the system.
These electrochemical impulses are the way information is exchanged in our bodies.
Think of the neurons as phone or network lines that make up the Internet and
the electrochemical impulses as e-mail, and you get idea. Just as e-mail is
used to send messages between people, electrochemical impulses are used to send message
between different body parts. In the body these messages can be things like:
 | Move the third finger on the left hand down. |
| Ouch! That hurts! Get that hand off the stove now! |
| Hey, that feels great! Keep it up! |
| I'm hungry, feed me! |
| This stuff tastes terrible! |
| It says that Christopher Columbus sailed the ocean blue in 1492. |
| That smells like roses. |
| Let's get that heart pumping, we're exercising! |
| Let's move those hips! |
| We have a wound at the right elbow! Send reinforcements! |
| It looks like a computer. |
| I'm tired of reading long, pointless, bulleted lists.
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A Simplified, Generic Neuron
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A single neuron is composed of a large cell body, the soma, and two cell parts: the
dendrites and an axon. The dendrites sends impulses to the soma while the axon sends
impulses away from the soma. Functionally, there are three different types of
neurons:
| Sensory neurons - They carry information from sense receptors (nerves
that help us see, smell, hear, taste, and feel) to the central nervous system which
includes the brain and the spinal cord. |
| Motor neurons - They carry information from the CNS to effectors
(muscles or glands that release all kinds of stuff, from water to hormones to ear wax) |
| Interneurons - They connect sensory neurons and motor neurons.(Heller,
156) |
Now, how do these things work? Inside and just outside of the neurons are sodium
ions(Na+) and potassium ions(K+). Normally, when the neuron is just sitting not
sending any messages, K+ accumulate inside the neuron while Na+ is kicked out to the area
just outside the neuron. Thus, there is a lot of K+ in the neuron and a lot of Na+
just outside of it. This is called the resting potential. Keeping the K+ in
and the Na+ is not easy, it requires energy from the body to work. An impulse coming in
from the dendrites, reverses this balance, causing K+ to leave the neuron and Na+ to come
in. This is known as depolarization. As K+ leave Na+ enter the neuron, energy
is released, as the neuron no longer is doing any work to keep K+ in and Na+ out.
This energy creates an electrical impulse or action potential that is
transmitted from the soma to axon. As the impulse leaves the axon, the neuron repolarizes,
that is it takes K+ back in and kicks Na+ out and restores itself to resting potential,
ready to send another impulse. This process occurs extremely quickly. A neuron
theoretically can send roughly 266 messages in one second.(Heller 157) The
electrical impulse may stimulate other neurons from its synaptic knobs to proprogate the
message. The entire neuron system can be described as neural networks.
In AI, researchers try to simulate a neuron with computer and connect that computer
with other computers in an artificial neural network.
The task at hand in these kinds of networks is to effectively break up information so that
it can evenly distributed to the individual computer neurons to be processed
simultaneously just as a biological brain does. More on this process can be found in
"The Future--Faster Computing." |
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