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Virgil:Basic Neuroanatomy

I'm going through some neuroscience books, and I thought the world might be interested in the parts of their brains that are operating right now even as they're reading the texts. Generally, these sort of introductions come in two varieties. One for middle school students and the other for entry medical students. However, for most people neither of these approaches helps them much. So, I will attempt to describe things somewhere between these two levels of complexity and hope it makes some sense.

Questions/Feedback greatly appreciated.

The Cortex


The brain is divided into two primary sections. The cortex and the subcortex. The cortex is the outer surface of the brain (the cerebrum anyway) and is only 1.5-5mm deep. The cortex is has significantly denser neural connectivity than any other part of the brain. The cortex is especially associated with non-life-sustaining cognitive functions. Things like feeling, sensory perception, higher cognition, etc. are all primarily in the cortex. What is especially interesting about the neurons in the cortex itself is that they are look about the same, they are simply networked differently. This is very nice because it means that we can likely establish some general principles of the neural basis for intelligent behavior simply by using networks of identical individual neurons.

Facts about Individual Neurons

  • A Neuron is a single cell
  • Thus, they have a cellbody, nucleus, phoso-lipid membrane, has fluid, mitochondria, organelles, and all of the other things we've come to expect in traditional cells.
  • Has DNA, and performs protein synthesis
  • There are about 100 billion of these things in the human brain. However, they differ from traditional cells in a few small ways.
  • They have these odd long things called axons and dendrites coming from their core.
  • These axons and dendrites

  • The cortex and neocortex are the same thing. The term 'neocortex ' merely makes note of the fact that the cortex is relatively recent in evolutionary theory.

    here's a nice picture of the neocortex for your viewing pleasure.

    On Feb 17, 2006, at 8:34 AM, Chris Waggoner wrote:

    This is just what I am looking for. Comments as I go:

    -some grammar mistakes and typoes in first two paragraphs

    -what does " feeling, sensory perception, higher cognition, etc. are all primarily in the cortex" mean?

    -"simply by using networks of identical individual neurons" -- do you mean theoretical neural networks or synthetic neurons?

    -what is phoso-lipid membrane and its significance?

    -"There are about 100 billion of these things in the human brain." That's 10^8? Is 10^8 big or small?

    -I guess you're not finished -- what is the significance of axons and dendrites? As I understand it dendrites spread roots wide to receive electrochemical juices and axons shoot electrochemical juices - thus propagating a signal. (How does this lead to a neural net?)

    -why do I care about neocortex in the first place?


  • Neocortex/cortex (the outer layer of the brain) is basically where everything interesting (anything thinking) happens.
  • Basically all of cortex is made up on the same types of neuron (pyrimidal neurons), but their connectivity is vastly different. But individually, every neuron is basically the same and has the same basic properties.
  • the phoso-lipid membrane is the conduit by which neurons transmit signals to another neuron.
  • 10^8 just is. I dont know if it's supposed to be big or small. I guess that for a brain it's pretty big since humans have the largest brains around.
  • (last modified 2006-02-17)       [Login]
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