Structure of the nervous system | Organ Systems | MCAT | Khan Academy

In this video I’m going to introduce the structure of the nervous system and the nervous system is divided into.


In this video I’m going to introduce the structure of the nervous system and the nervous system is divided into two main structural parts. The first is called the
central nervous system. And the second is called the
peripheral nervous system. Central and peripheral, and both of those are themselves divided into two main parts. The central nervous system is
made up mostly of the brain which is in the head. So I’ll just color that
in here in magenta. And the spinal cord which is in the spine. So I’ll just color that in in blue. That’s this long thin tube-like structure that goes down the spine. Now the brain is divided into
a bunch of different parts. And I’ll just mention some of the big ones for this kind of introduction talk. Here we’re looking at the
brain from the left side. All of this part on the top, that has several different colors here, is called the cerebrum. Cerebrum, which is the
biggest part of the brain and the part on top. Now if we look down from the top, like in this drawing here, you can’t see the parts underneath. You can only see the cerebrum and you see that it’s divided into a left and a right half, and we call those halves the cerebral, or cerebral hemispheres. Cerebral hemispheres, like half a sphere. And there’s a left and a
right cerebral hemisphere. Now on this picture over here, we’re actually looking at
the middle part of the brain, so it’s like we’ve cut
down the brain this way, and separated the left and
the right cerebral hemisphere. So here we’re looking at the
left cerebral hemisphere, but we’re looking at
it from this direction. And we see that all of
this stuff on the top, is the cerebrum or one of
the cerebral hemispheres, and then the part on the bottom, which is smaller, we divide into two other parts. So first let me just draw an outline around this part right here, and this is the part that hooks onto the spinal cord down here. And this part is called the brain stem. Let me write that out, brain stem, which is all of this part right here that connects the cerebrum
to the spinal cord that they’ve cut off down
here on this picture. And then the brain stem itself is divided into three smaller parts. The very top part of the brain stem that connects to the cerebrum, is called the mid brain, mid brain. And the middle part that’s
just below the mid brain we call the pons, P-O-N-S, for pons. Under the pons, and the part that actually
connects to the spinal cord, is called the medulla, or medulla, or sometimes people use a longer name of medulla oblongata. And then the last part, but not the least part of the brain, is this big part in the back. It’s behind the brain stem and connected to the brain stem. And this, we call the cerebellum. Cerebellum. Now sometimes brain
structures are referred to by the names of the structure
that they develop from in the embryo. So here’s a picture of the human embryo and it’s developing it’s brain here. And this very front part
is called the fore brain or it has a longer name of prosencephalon. This part behind the fore
brain is called the mid brain and it also has a longer name called the mesencephalon. And then the part behind the mid brain is called the hind brain, hind brain, and it also has a longer name of the rhombencephalon. So the fore brain is going
to become the cerebrum. The mid brain is going
to become the mid brain. Just this part of the brain stem, up top. And then the hind brain will
become the rest of the brain. The pons, the medulla, and the cerebellum. So just in case you
hear people referring to structures in the brain by these names, that’s where those names come from. They’re from the
developing nervous system. Here’s a drawing of the spinal cord. This kind of long tube
that runs down the spine. And there’s a number of structures coming out of the spinal cord that I’ll talk about next. So those are the parts that make up most of the central nervous system, and everything that’s not in
the central nervous system we call the peripheral nervous system. And the central nervous
system is called that because it’s kind of in
the center of the body and then the peripheral
nervous system is called that because it’s going to go out
all over the rest of the body. The peripheral nervous system consists of two types of structures. The first are called nerves. Let me just underline
this nerve right here. And these are the long stringy structures that are going to go all over the body. And nerves carry the axons of neurons. The second main structure of
the peripheral nervous system are called ganglion. Ganglion is singular
and ganglia is plural. And ganglia are these lumps
that are attached to nerves and they contain the somas of neurons. Now let me just draw
that a little differently over on this picture of the spinal cord that have these nerves coming out of it. So here’s one of these lumps, one of these ganglia
that contains the somas of some of the neurons in
the peripheral nervous system and some of these axons
traveling through these nerves are going to be carrying information in to the central nervous system from the periphery. So they’re going to bring
information in this way from out here in the periphery. And when they do that, we call those afferent neurons, afferent neurons carry information in to the central nervous system. Now other neurons are going to have axons that carry information in
the opposite direction. So they’re going to carry information away from the central nervous system out into the periphery. And neurons whose axons carry information away from the central nervous system we call efferent neurons. Efferent neurons. Now there are lots of these nerves that are going all over the body. And you can divide them up
in a few different ways. But we usually start by dividing them into the cranial nerves which are nerves that exit
the skull or the cranium. So these nerves primarily
come out of the brain and they’re passing through
the skull on their way between the central nervous
system and the periphery or the peripheral nerves
can be spinal nerves. And they’re coming out of the spinal cord and passing through the spine on their way between the central nervous
system and the periphery. And I’ll just draw a few of these, but there’s actually lots of these. They’re paired on both sides of the body. And there are 12 pairs of cranial nerves and 31 pairs of the spinal nerves. Now if we go back to our
drawings of the spinal cord here, we can see that the spinal nerves actually form from these two parts which are called spinal nerve roots and there’s a root in the front and there’s a root in the back. And in this drawing we’re
looking from the back. So here’s the root in the
back that have the ganglia and the way these spinal nerve roots work are that the afferent neurons bringing information into
the central nervous system travel through the spinal
nerve roots in the back and the efferent neurons that are carrying information away from the central nervous system travel in the spinal
nerve roots in the front and then they come together
in the spinal nerves, so we call those mixed nerves because they have a mix of afferent and efferent neurons usually. Now as any of these nerves travel from their proximal origin, proximal just meaning close
to the center of the body, toward their distal ends, the word distal just meaning far away from the center of the body, or you can think of the word distant, all the nerves are going
to branch repeatedly, so they’re going to branch, and then they’ll branch, and then they’ll branch again, and they’ll just keep branching into tinier and tinier branches, because they have a long way to go and have to spread all the way out all the way through the body, and these proximal parts of the nerves are big nerves that we can
see with the naked eye. But once you get to these distal nerves, after they’ve branched a bunch of times, actually become microscopic, and they’re little microscopic nerves that go all over the body connecting the entire body back to the central nervous system. And this is true for almost all of the cranial and the spinal nerves. Oh, I almost forgot here, I have this other drawing
to show the cranial nerves. Here’s a drawing of the brain looking up from the bottom, and all of these long
stingy looking things coming out of the brain are cranial nerves. They’re going to pass through the skull on their way from the brain out into the periphery. I won’t draw them all in here, but there are a bunch
of these cranial nerves that are going to pass through the skull. So that’s a brief kind of overview of the structure of the nervous system and there’s a lot more to it of course. But I just want to give
you an introduction here. And we’ll get into some
more of the details in later videos.

65 thoughts on “Structure of the nervous system | Organ Systems | MCAT | Khan Academy”

  1. Khan is literally the best person in education! He really should win a nobel prize of education or something! he ris revolutionizing educationย 

  2. It bothers me that you like to say "CA-ra-bal" instead of "ce-RE-bral"…I've never heard anyone say that before

  3. Will you make a video going more into detail regarding the hemispheres and the different layers that surround/protect the brain. ie, meningeal, epidymal, and all the sub layers? Thanks!

  4. Thanks, we have an eog coming up and the teachers didnt have time to teach us a ton about certain systems, and i want them to get paid, especially my teacher since she has a baby on the way, really good.

  5. Well done and thank you! Man…this is a complex piece of our anatomy andย  something I need to understand better. This was a great place to start…you speak slowly with passion in your voice and deliberately as well.ย  I enjoyed it…

  6. I found it very helpful with the beginning of my psychology course knowing the how the workings of the brain and where to find where out thought come from biologically

  7. Absolutely loooove Khan Academy's videos, they help me understand everything. Just wanted to say that this guy sounds like Cleveland from Cleveland Show, which keeps it interesting for me ๐Ÿ˜€ Keep it up!

  8. Whoever is the person speaking, I honestly can not concentrate on the subject. The voice is so annoying,… sorry for saying that. I love all the khan academy videos though, incredibly useful.

  9. Why don't you explain how the government's are killing us via electro magnetic fields thru attacking humans with microwaves being beamed at the brains of individuals from satellite from all over the world by the demonic forces at NASA, CERN, DARPA, etc.

  10. If you find his voice slightly monotone and hard to listen to, change the speed to 1.25. He sounds more upbeat but it's still at a pace that you can follow.

  11. ill pray for you Khan. I just dont think thank you is enough. I think we should pay you instead of those teacher we have.

  12. No need for teachers in the US or anywhere in the world. Education should be offered online, and these videos from Khan Academy will make the student successful. Love the videos.

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