the cerebral cortex is the surface of the brain and we talked about this a
little bit in the introduction in gross anatomy of the brain we pointed out all
of the different this cell site which are the great big divots in between and the
gyri which are the kind of the bumps this is your neocortex your neocortex means new cortex
okay and it's unique to mammals so reptiles don't have it birds don't have it fish don't
have it it's a mammal thing so be proud that you're a mammal and you have neocortex the
surface area of the cortex we talked about when we talked about gross anatomy we thought
I mentioned that your brain is too big for your head and the fact is that then that's why it's
in all these folds these sulci and gyri so if you could take your cortex and flatten it out
it would be about 2.5 square feet so about the size of a newspaper and so if you think about
that you think about taking a newspaper and kind of turning it into a balloon that's how
big your head would have to be if we didn't have cell science I write the cortex is about 80% the
mass of your brain and it's where you think it is really where you as a person exists in your
nervous system so everything that's unique to you is because of your cortex and is a property
of your cortex it's influenced greatly by all of the sensory information that's coming in from the
outside everything you see and hear and smell and feel and internal stuff the internal workings of
your own body the things that are that your your central nervous system can sense and you can kind
of self generate you think your own thoughts so there are multiple levels of stimulation
that are being integrated within this within the central nervous system and most of it is going to
integrated in the cerebral cortex so as we said Newark neocortex is new cortex and it's six layers
and we can see some of those layers here in this cartoon we can see there's there's layers one
through six there's an outer kind of molecular layer there are layers 3 & 5 which are these
great big pyramidal cell layers and then there's layers 2 & 4 & 6 which are receptive layers we'll
talk a little bit more about those when we talk about cytoarchitecture our key cortex or paleo
cortex think about archeology or the Paleolithic period those are both terms that mean old and so
there is old cortex in your brain leftover from you know evolutionarily speaking and one area
of this is found in the hippocampus old cortex only has 3 layers so again layers 1 through 6
are superficial to deep so layer 1 is out here layer 6 is here and there are basically layers
that send information and layers that receive information the layers that send information are
these layers that have the great big cell bodies because if you think about it if you're sending
information all the way from your cortex think about the motor system all the way down maybe
to the bottom of your spinal cord you've got a really long axon to maintain and if you have a
really long axon to maintain you've got to have a really big cell body to maintain that axon if
you are a layer that receives so you're getting all kinds of information you want to have a whole
bunch of different neurons in there so areas like this like would receive an area for
is big into receiving and you have big dendritic arbors so lots and lots and lots of areas
for synapses take to take place I'm going to erase and turn my drawing tool back on what I also want
you to know is it depends on how you look at the cortex so this image is a Golgi stain is a kind of
an artist rendition of a Golgi stain Golgi stains were discovered kind of accidentally by dumping
a chunk of the brain into some heavy metals we don't know exactly how it works still to this day
we don't know how it works but the bottom line is that the heavy metals will fill up the entire cell
body and its axons and dendrites it doesn't fill up every cell because if it did it would be just
one big black chunk of tissue but it does fill up the odd neuron here and there nobody knows
why some neurons are filled in some aren't but it works really well to see the entire architect
architecture of a single cell the middle panel is a nissl stain nissl substance is big stacks of
rough endoplasmic reticulum which are responsible for making proteins and so neurons make a lot of
proteins they make neurotransmitters they make all kinds of proteins to put into their channels and
their receptors and so those this stain sustains mostly the cell body so you don't see a lot of
processes but you see the shape of the cell body and it stains almost all of them so you have a
different look if you see use a nissl stain versus a Golgi stain in this last panel we've stained for
myelin and myelin is that lipid rich coating that surrounds all of the axons to keep them from from
to keep crosstalk from happening so if you have a signal going down one wire you want it going only
down that wire and not down another one and so you have to keep them insulated it's just like the
insulation on the wires in your house so two axons side by side have to be insulated from one another
and is what myelin does and if you stain for the myelin what you notice are these columns of cells
separated by these bands of fibers that are going along this kind of making these columns within
the cortex well it turns out that these columns are kind of the functional unit of the cortex so
neurons within a column are working together and then they talk to the neurons in the next column
or in the next column this way but these guys are all working together in the next section
we'll talk about more of the sito architectonics and what that means with regard to function