In this video, I
want to introduce the different types
of neural cells. The word "neural" or
the prefix "neuro" just refers to the
nervous system, so that neural cells are
cells of the nervous system. Neural cells work with all the
other cell types of the body to produce the amazing
range of functions of the nervous system,
including consciousness, social interactions,
cognition, emotion, movement, sensory perception, and
regulation of other functions, such as circulation,
respiration, and digestion. Neural cells are divided
into two big categories. The first are neurons,
which were traditionally called nerve cells. And the second are glia. Now, these can also be called
neuroglia or glial cells. That all means the same thing. Neurons are named from
a Greek word for nerve, while glia are named from
a Greek word for glue, because they were once
thought to do little except glue neurons together. The structure of
the nervous system is divided into two main parts. The first part is mainly
made up of the brain in the head and the
spinal cord in the spine. And this part of
the nervous system is called the central
nervous system. The other part of
the nervous system is called the peripheral
nervous system. And that's made up
mostly of nerves, these long, stringy
structures that come out of the brain and
the spinal cord. And they go all over the
body, like down into the arms, and down into the legs, and
into every part of the body. And we'll cover a lot more
in detail about neuroanatomy in other videos. But I just need to bring up the
central and peripheral nervous system because the neural cells
are divided up differently amongst the different systems. Calling neurons nerve cells
is a little problematic because these structures in
the peripheral nervous system called nerves are
made up of neurons. But they also
contain glial cells. And they contain a
number of other cells that aren't neural cells at all. However, you'll
often hear people refer to neurons as
nerve cells because that was the traditional
name for them. Neurons are found both in
the central nervous system, the brain and the spinal cord,
and the peripheral nervous system, in the nerves. But the different
types of glial cells are found only in
one or the other. Most neural cells are
derived from populations of cells called neural stem
cells or neural crest cells. And both of those cell types
arise early in development in the part of the embryo
called the ectoderm. Most neurons and glia found
in the central nervous system are derived from
neural stem cells, while most neurons
and glia found in the peripheral nervous system
are derived from neural crest cells. Now, we'll go into a lot more
detail about what neural stem cells are and neural crest cells
in other videos, when we cover development of the
nervous system. Most types of both
neurons and glia share some structural
features of the way their cell is shaped. Most of them have a main
part to their cell called the soma or the cell body that
contains the nucleus and most of the organelles. Coming out of the soma,
most of these cell types have processes,
long, thin extensions that come out of the soma. And the processes of the
different neural cells vary in number and in length,
in thickness, and degree of branching, because some
of them will be unbranched, and some of them
will have processes that branch, sometimes a
little and sometimes a lot. They will also vary a lot
in the terminal structures at the end of their
processes and the function of these structures
and the processes. The function of neurons
is to process and transmit information. And the function of
glia is to support them in a variety of ways. There are many structural
and functional types of both the neurons
and the glia. And there are large numbers
of these cells making up the nervous system. There are billions
of neurons that form trillions of connections in
the adult human nervous system. And there even more glia
than there are neurons. In subsequent videos, we'll
go over the most common glia, which are astrocytes,
microglia, ependymal cells, oligodendrocytes,
and Schwann cells. There are also less common
glia, such as satellite cells and olfactory and
sheathing cells. But we'll just go over the
most common types here.