Anatomy of a neuron | Human anatomy and physiology | Health & Medicine | Khan Academy

We could have a debate about
what the most interesting cell in the human body is, but I
think easily the neuron would make the top five, and it’s
not just because the cell itself is interesting. The fact that it essentially
makes up our brain and our nervous system and is
responsible for the thoughts and our feelings and maybe for
all of our sentience, I think, would easily make it the
top one or two cells. So what I want to do is first
to show you what a neuron looks like. And, of course, this is kind
of the perfect example. This isn’t what all
neurons look like. And then we’re going to talk
a little bit about how it performs its function, which is
essentially communication, essentially transmitting signals
across its length, depending on the signals
it receives. So if I were to draw
a neuron– let me pick a better color. So let’s say I have a neuron. It looks something like this. So in the middle you have your
soma and then from the soma– let me draw the nucleus. This is a nucleus, just like
any cell’s nucleus. And then the soma’s considered
the body of the neuron and then the neuron has these little
things sticking out from it that keep
branching off. Maybe they look something
like this. I don’t want to spend too much
time just drawing the neuron, but you’ve probably seen
drawings like this before. And these branches off of the
soma of the neuron, off of its body, these are called
dendrites. They can keep splitting
off like that. I want to do a fairly reasonable
drawing so I’ll spend a little time
doing that. So these right here, these
are dendrites. And these tend to be–
and nothing is always the case in biology. Sometimes different parts of
different cells perform other functions, but these tend to be
where the neuron receives its signal. And we’ll talk more about what
it means to receive and transmit a signal in
this video and probably in the next few. So this is where it receives
the signal. So this is the dendrite. This right here is the soma. Soma means body. This is the body
of the neuron. And then we have kind of a–
you can almost view it as a tail of the neuron. It’s called the axon. A neuron can be a reasonably
normal sized cell, although there is a huge range, but the
axons can be quite long. They could be short. Sometimes in the brain you might
have very small axons, but you might have axons that
go down the spinal column or that go along one of your
limbs– or if you’re talking about one of a dinosaur’s
limbs. So the axon can actually
stretch several feet. Not all neurons’ axons
are several feet, but they could be. And this is really where a lot
of the distance of the signal gets traveled. Let me draw the axon. So the axon will look
something like this. And at the end, it ends at the
axon terminal where it can connect to other dendrites or
maybe to other types of tissue or muscle if the point of this
neuron is to tell a muscle to do something. So at the end of the axon,
you have the axon terminal right there. I’ll do my best to draw
it like that. Let me label it. So this is the axon. This is the axon terminal. And you’ll sometimes hear the
word– the point at which the soma or the body of the neuron
connects to the axon is as often referred to as the axon
hillock– maybe you can kind of view it as kind of a lump. It starts to form the axon. And then we’re going to talk
about how the impulses travel. And a huge part in what allows
them to travel efficiently are these insulating cells
around the axon. We’re going to talk about this
in detail and how they actually work, but it’s good
just to have the anatomical structure first. So these are
called Schwann cells and they’re covering– they make
up the myelin sheath. So this covering, this
insulation, at different intervals around the
axon, this is called the myelin sheath. So Schwann cells make up
the myelin sheath. I’ll do one more
just like that. And then these little spaces
between the myelin sheath– just so we have all of the
terminology from– so we know the entire anatomy of the
neuron– these are called the nodes of Ranvier. I guess they’re named
after Ranvier. Maybe he was the guy who looked
and saw they had these little slots here where you
don’t have myelin sheath. So these are the nodes
of Ranvier. So the general idea, as I
mentioned, is that you get a signal here. We’re going to talk more about
what the signal means– and then that signal gets–
actually, the signals can be summed, so you might have one
little signal right there, another signal right there, and
then you’ll have maybe a larger signal there and there–
and that the combined effects of these signals get
summed up and they travel to the hillock and if they’re a
large enough, they’re going to trigger an action potential on
the axon, which will cause a signal to travel down the
balance of the axon and then over here it might be connected
via synapses to other dendrites or muscles. And we’ll talk more about
synapses and those might help trigger other things. So you’re saying, what’s
triggering these things here? Well, this could be the terminal
end of other neurons’ axons, like in the brain. This could be some type
of sensory neuron. This could be on a taste bud
someplace, so a salt molecule somehow can trigger it or a
sugar molecule– or this might be some type of sensor. It could be a whole bunch of
different things and we’ll talk more about the different
types of neurons.

100 comments

  1. This was a very helpful video, thank-you. Does anyone know if there is a video that explains the transmission of a nerve signal using a ion gradient? Preferably Khan because the video's are clear but I am open to anything 🙂

  2. Schwann cells myelinate axons only in the Peripheral Nervous system. In the Central Nervous system, Oligodendrocytes are the myelinators.

  3. But the schwann's cells and the myelin sheath aren't the same thing ! the schwann's cell lyes over the myelin sheath which sourrounds the axon .

  4. I love your videos! You have helped me I understand complex subjects. Please make more videos on anatomy & physiology of the human body & the pathophysiology of diseases!! I am a RN student in need to clarification. Thanks again for all your great video!!

  5. Wow. Superb vid.

    My dad was formerly a flabby. He improved his body from 290 lbs of fat to 203lbs of full-strength lean muscle mass. His pals were shocked. I just joined personally because I would like to greatly improve my entire physique. He made use of the Muscle Building Bible (Look in Google)…

  6. Is this video continued somewhere, and is so can someone link it please. I cant find any myself. I missed some explanation of the difference between unipolar, pseudounipolar, bipolar and multipolar neurons. Great video though!

  7. I can't find the end of this video. I looked in the biology playlist and I couldn't find a continuation anywhere, though there is a private video there, could that be it? Is there anyone who has a link to the rest of the video?

  8. Thank you for you amazing videos. I am also a teacher. What format/program are you using for these videos? Connie
    Does anyone else know?

  9. Wow! Amazing! Beautifully done–watching the illustration happen helps me visualize it more than just seeing the finished product. Great video!

  10. I believe my Biology book is trying to make everything complicated, so the author can be seen as an intellectual. Students in introductory courses would learn much better with straight-forward teaching, like here. Thank you Salman!

  11. "Anatomy of a neuron" imo is a too broad term to deal with. There is a variety of neurons in the different parts of the CNS and PNS with differing morphological characteristics. Nevertheless, a very good basic explanation.

  12. Lovely drawings and captivating voice
    i loved and understood the video 
    Thank you sooooo much
    long live khan academy<3

  13. A perfect story about neuron, I wish there is more videos with this subject. Another resource I also found useful for human anatomy body is Moorack Simple Anatomy Miracle – it will be on google if you need it.

  14. So if you were to take the nucleus of a neuron, and replace the nucleus in a nuke with the nucleus of a neuron, and the bomb was detonated… Does that mean your mind was blown?

  15. Gandalf-
    Quickly Hobbits, we must now cross the Sheaths of Myelin and down into the Nodes of Ranvier. For therein resides the Lady of the Neurofilimantes, whose control of the Schwann we require.

  16. It should be noted that upon talking about the anatomy, one should distinguish between the CNS (Central Nervous System) and the PNS (Peripheral Nervous System), since the CNS has the oligodendrocytes as an insulator wrapped around the axon, whereas the PNS has the Schwann cells. They both do more or less the same job, yet the structure is different. Of utmost importance is the fact that the Schwann cells are the only ones capable of axonal regeneration after damage in mammals, which explains why such process is only feasible on the PNS.

  17. salman khan i have a doubt
    what is the difference between neuron and a nerve cell
    are they same or different

  18. Wow, my bio teacher compares nothing to this channel. Oh my goodness. The videos are extremely helpful.

  19. So thankful for your professional clear cut videos. Its 2am and i just wanna learn and you help me and im stoned so thanks.

  20. i like your video, thankyou so much.
    but my english is poor,
    can you put Indonesian,
    thanks before

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