00:01
Now, just imagine that this butterfly
or this area of gray matter
is travelling all the way up and down the
spinal cord, as is the white matter.
00:15
You are only looking at a single section or two in
this image, a very thin section through the
spinal cord. But as I said imagine this area
of gray matter moving or being present all
the way up and down the spinal cord, so you
can then imagine the enormous numbers of ventral
horn cells there may be and the enormous numbers
of sensory neurons coming into the dorsal
horn, all the way on the spinal cord, very
fascinating concept. Of course you can see
that the gray matter is different in both
these images. And that is because the gray
matter in the image on the left hand side
is probably only housing motor neurons that
might innervate muscles of the torso. So this
is a section probably through the thoracic
region of the spinal cord. Muscles of the torso are
less in number than the muscles that we have
that move our upper limb or our lower limb. And
therefore we have the need for a lot more
these ventral horn cells in the regions of
the spinal cord where these ventral horn cells
are going to exit and form peripheral nerves.
So that is why you see the difference in the
size of the gray matter as you move up and
down the spinal cord. It is also pretty easy
to understand or to identify what is a ventral
horn and what is a dorsal horn because the
ventral horn as you see on the right hand
side is generally a lot larger, a lot more
elongated as well, than the dorsal horn.
02:06
So in summary, you should understand the structure
of the nerve cell. Remember, the cell body
is called the soma. Lots of rough endoplasmic
reticulum inside the cell is referred to as
nissil substance. And the main processes of
the nerve cell is the long axon.
02:29
The dendritic branches that receive information and
the axons can be myelinated or unmyelinated.
02:37
And also between the myelin sheath and the myelin
axon is the node of Ranvier, which enhances
the transmission of the impulse along the
axon. You should also understand the divisions
of the nervous system, both anatomically and
functionally. And finally you should know the
structure of the spinal cord and the different
functional components within that spinal cord,
because that is going to be the subject of
a later lecture. So thank you very much for
listening to this lecture. I hope you have enjoyed
learning about the neuron, the structure of
the spinal cord and the general organization
of the nervous system.