Neurology | Neuron Anatomy & Function

00:44:33
https://www.youtube.com/watch?v=qOmmqu6_g3s

الملخص

TLDRIn this video, the structure and function of neurons are thoroughly explained, outlining key components such as dendrites, soma, axon, and axon terminals. Each component's role in the transmission of signals and communication between neurons is explored, including the process of action potentials and neurotransmitter release. The video also discusses synaptic functions like graded potentials (EPSP and IPSP) and the importance of reuptake mechanisms. Additionally, neurons are classified into multipolar, bipolar, and pseudo-unipolar types based on structure, and functionally into sensory, motor, and interneurons for effective communication within the nervous system.

الوجبات الجاهزة

  • 🧠 Neurons consist of dendrites, soma, axon, and axon terminals.
  • 🔗 Dendrites receive signals and are involved in graded potentials.
  • ⚡ The axon conducts action potentials away from the soma.
  • 🧪 Neurotransmitter release occurs at the axon terminal during synaptic transmission.
  • 🔄 Reuptake of neurotransmitters is crucial for synaptic function.
  • 📊 Neurons are classified into multipolar, bipolar, and pseudo-unipolar types.
  • 💡 Interneurons connect sensory and motor pathways in the CNS.
  • 📈 Action potentials are rapid signals along the axon.
  • 🔋 EPSP and IPSP are critical for neuron depolarization and hyperpolarization.
  • 🧬 Protein synthesis in the soma is essential for neuronal function.

الجدول الزمني

  • 00:00:00 - 00:05:00

    The video introduces the topic of neurons, emphasizing the importance of structural and functional understanding. Viewers are encouraged to engage with the content through likes, comments, and subscriptions while providing links to social platforms.

  • 00:05:00 - 00:10:00

    The structure of neurons is explained, focusing on key components: dendrites, cell body (soma), axon, axon hillock, and axon terminals. Dendrites are characterized as the receptive zones, while the axon is responsible for conducting action potentials.

  • 00:10:00 - 00:15:00

    Dendrites' functions are explored, highlighting ligand-gated ion channels that facilitate synaptic connections. This leads to the creation of excitatory postsynaptic potentials (EPSPs) or inhibitory postsynaptic potentials (IPSPs), which are fundamental concepts in graded potentials.

  • 00:15:00 - 00:20:00

    The cell body (soma) is discussed not only for its role in receiving graded potentials but also for its critical function in protein synthesis, including neurotransmitters and membrane proteins, through processes involving DNA transcription to mRNA and translation into proteins.

  • 00:20:00 - 00:25:00

    The axon is dissected, detailing its primary role in conducting action potentials. The structure of microtubules and motor proteins (kinesin and dynein) is explained, elaborating on anterograde and retrograde axonal transport for neurotransmitter vesicles and organelles.

  • 00:25:00 - 00:30:00

    The action potential's phases are clarified—depolarization (positive charge flow) followed by repolarization (negative charge flow) with specific voltage-gated sodium and potassium channels detailed. This section reiterates the importance of the axon's conduction functions.

  • 00:30:00 - 00:35:00

    The axon terminal is described as the secretory region where neurotransmitters are released, emphasizing the mechanisms of neurotransmitter reuptake and degradation. The clinical relevance of reuptake inhibitors in managing mood disorders is also addressed.

  • 00:35:00 - 00:44:33

    Lastly, the classification of neurons is presented, distinguishing between multipolar, bipolar, and pseudo-unipolar neurons based on structure, and then transitioning into the functional classification: sensory, motor, and interneurons, explaining their roles and importance in neuronal circuits.

اعرض المزيد

الخريطة الذهنية

فيديو أسئلة وأجوبة

  • What are the main components of a neuron?

    The main components of a neuron include dendrites, cell body or soma, axon (including the axon hillock), and axon terminal.

  • What is the function of dendrites?

    Dendrites receive signals from other neurons and are involved in graded potentials.

  • What is an action potential?

    An action potential is a rapid electrical signal that travels down the axon, initiated at the axon hillock.

  • What role does the axon play in neuronal function?

    The axon conducts action potentials away from the cell body to the axon terminal.

  • What is neurotransmitter release?

    Neurotransmitter release occurs at the axon terminal, allowing communication between neurons.

  • What are the different classifications of neurons?

    Neurons can be classified structurally (multipolar, bipolar, pseudo-unipolar) and functionally (sensory, motor, interneurons).

  • What is the function of interneurons?

    Interneurons connect sensory and motor neurons and process information within the central nervous system.

  • How do neurotransmitter reuptake inhibitors work?

    They block the reuptake of certain neurotransmitters, increasing their availability in the synapse.

  • What are synaptic vesicles?

    Synaptic vesicles store neurotransmitters until they are released into the synaptic cleft.

  • What is an EPSP and IPSP?

    EPSP (excitatory postsynaptic potential) depolarizes the neuron, while IPSP (inhibitory postsynaptic potential) hyperpolarizes it.

عرض المزيد من ملخصات الفيديو

احصل على وصول فوري إلى ملخصات فيديو YouTube المجانية المدعومة بالذكاء الاصطناعي!
الترجمات
en
التمرير التلقائي:
  • 00:00:14
    all right ninja nerds in this video
  • 00:00:15
    today we're going to talk about the
  • 00:00:16
    structure and function of
  • 00:00:18
    neurons all right guys before you guys
  • 00:00:20
    get started in this video please hit
  • 00:00:21
    that like button comment down in the
  • 00:00:23
    comment section and
  • 00:00:24
    please subscribe also down in the
  • 00:00:26
    description box we have links to all our
  • 00:00:27
    social media platforms for you guys to
  • 00:00:29
    interact with us
  • 00:00:30
    all right ninja nerds let's get started
  • 00:00:32
    all right ninja so the first thing that
  • 00:00:33
    we have to talk about when we're talking
  • 00:00:35
    about a neuron is obviously go over the
  • 00:00:36
    different structural components of a
  • 00:00:38
    neuron so what makes up a neuron
  • 00:00:40
    structurally
  • 00:00:41
    then we got to talk about what those
  • 00:00:43
    different components of a neuron
  • 00:00:46
    do all right so first things first when
  • 00:00:48
    you take a look at this neuron you see
  • 00:00:50
    these little
  • 00:00:50
    these little extensions coming off of
  • 00:00:52
    this big circular structure here
  • 00:00:54
    all these little extensions are called
  • 00:00:56
    dendrites that's the first thing i want
  • 00:00:58
    you to know
  • 00:00:59
    so the extensions that are coming off of
  • 00:01:01
    this neuron
  • 00:01:02
    is called your dendrites these are the
  • 00:01:05
    receptive zone we'll talk about what
  • 00:01:07
    that means
  • 00:01:08
    for a neuron next thing you have this
  • 00:01:11
    big circular structure here with a whole
  • 00:01:13
    bunch of stuff inside of it
  • 00:01:15
    this here is called your cell body or
  • 00:01:16
    your soma so this is called the cell
  • 00:01:18
    body
  • 00:01:20
    or also sometimes referred to as the
  • 00:01:22
    soma
  • 00:01:24
    the third part here of the act of the
  • 00:01:26
    actual neuron is this long elongated
  • 00:01:28
    portion here
  • 00:01:29
    that's going to be in between the cell
  • 00:01:32
    body
  • 00:01:33
    and the axon terminal okay this portion
  • 00:01:36
    here is called your
  • 00:01:37
    axon so this third part here is called
  • 00:01:39
    your axon
  • 00:01:41
    now i have to add in one more little sub
  • 00:01:43
    component of the axon it's important
  • 00:01:45
    because it's going to come up when we
  • 00:01:47
    talk about action potentials
  • 00:01:49
    the part where the cell body kind of
  • 00:01:51
    like narrows and goes
  • 00:01:53
    into this kind of like thin axon
  • 00:01:55
    structure
  • 00:01:56
    is called the axon hillock so remember
  • 00:01:59
    whenever you're looking at an axon like
  • 00:02:00
    this if i were to draw another
  • 00:02:02
    small version of it like this there's a
  • 00:02:06
    part where the cell body starts to
  • 00:02:08
    narrow
  • 00:02:09
    that portion where the cell body kind of
  • 00:02:11
    like narrows like a funnel
  • 00:02:12
    this portion here is referred to as the
  • 00:02:15
    axon hillock
  • 00:02:16
    okay so when you're talking about the
  • 00:02:18
    axon a special part to remember
  • 00:02:21
    is called the axon hillock the reason
  • 00:02:24
    why this area is important is because
  • 00:02:26
    there's a high concentration
  • 00:02:28
    of voltage-gated sodium channels there
  • 00:02:30
    so whenever action potentials are
  • 00:02:32
    generated they're generated here
  • 00:02:34
    and move down the axon okay this last
  • 00:02:38
    portion here of the neuron
  • 00:02:39
    is this little kind of bulbous like
  • 00:02:41
    structure here of the neuron coming off
  • 00:02:42
    the axon
  • 00:02:43
    and this is called the axon terminal or
  • 00:02:46
    the synaptic terminal
  • 00:02:47
    i'm just going to write axon terminal
  • 00:02:51
    and sometimes you might even hear it
  • 00:02:52
    written as axon terminal
  • 00:02:54
    bulb or synaptic bulb
  • 00:02:57
    there's a bunch of different synonymous
  • 00:03:00
    terms there okay
  • 00:03:01
    so we got all the different components
  • 00:03:03
    of a neuron let's talk about what their
  • 00:03:05
    functions are
  • 00:03:05
    first all right so now let's go to start
  • 00:03:07
    talking about the functions of these
  • 00:03:09
    different
  • 00:03:10
    areas of the neuron right so we talk
  • 00:03:12
    about the dendrites right
  • 00:03:14
    so what you want to think about here is
  • 00:03:16
    that we're actually looking at one of
  • 00:03:17
    these
  • 00:03:18
    dendrites here coming off right and
  • 00:03:20
    we're kind of going to
  • 00:03:21
    cut into this right and really zoom in
  • 00:03:24
    on it in this view
  • 00:03:25
    so we're taking this dendrite taking a
  • 00:03:27
    section of that cell membrane and
  • 00:03:28
    looking at it here
  • 00:03:30
    now another thing to add on to that is i
  • 00:03:33
    want you to imagine this is what we're
  • 00:03:34
    going to call our postsynaptic neuron
  • 00:03:37
    that means that there's going to be
  • 00:03:38
    other neurons that are synapsing
  • 00:03:40
    on this postsynaptic neuron so let's
  • 00:03:44
    imagine here that you have
  • 00:03:45
    other neurons interacting at that site
  • 00:03:48
    that we're going to zoom in on
  • 00:03:49
    when we zoom in on that we got some
  • 00:03:51
    proteins that you guys need to know
  • 00:03:53
    because they're relevant to the function
  • 00:03:54
    of the dendrite
  • 00:03:56
    in this dendritic cell membrane part
  • 00:04:00
    you have these special types of channels
  • 00:04:02
    what are these special types of channels
  • 00:04:05
    these channels that are present on the
  • 00:04:06
    dendrites are called your ligand
  • 00:04:10
    gated ion channels
  • 00:04:14
    and these are important because they are
  • 00:04:16
    involved in formation of epsps
  • 00:04:20
    and ipsps what the heck is that zach
  • 00:04:23
    i'll explain to you what that means
  • 00:04:26
    these neurons
  • 00:04:27
    right imagine here i have kind of like a
  • 00:04:29
    little neuron here
  • 00:04:30
    like a little axonic extension and it's
  • 00:04:32
    releasing out a neurotransmitter
  • 00:04:35
    okay that neurotransmitter
  • 00:04:38
    what it's going to do is is it's going
  • 00:04:41
    to come here
  • 00:04:42
    and bind into this little pocket okay
  • 00:04:45
    on this ligand-gated ion channel when it
  • 00:04:46
    binds onto the pocket there's normally
  • 00:04:48
    like a little valve if you will that's
  • 00:04:50
    blocking this opening for ions to come
  • 00:04:52
    in
  • 00:04:52
    like this but once this little
  • 00:04:54
    neurotransmitter binds onto that pocket
  • 00:04:56
    it causes that valve fuel to open up and
  • 00:04:59
    then allows for positive ions
  • 00:05:02
    to move into the cell making the cell
  • 00:05:05
    nice and positive that's called
  • 00:05:07
    depolarization when you make the cell
  • 00:05:09
    more positive or less negative if you
  • 00:05:11
    will
  • 00:05:12
    and that is referred to as a
  • 00:05:15
    depolarization right when you make it
  • 00:05:17
    more positive and that's called an epsp
  • 00:05:19
    you're trying to stimulate the neuron to
  • 00:05:22
    fire or generate an action potential and
  • 00:05:25
    the other aspect let's say that you have
  • 00:05:26
    another neuron over here maybe it's this
  • 00:05:28
    one
  • 00:05:29
    and you have the axon here and this axon
  • 00:05:31
    is releasing another neurotransmitter
  • 00:05:33
    but instead of this neurotransmitter
  • 00:05:34
    being stimulatory let's have the
  • 00:05:36
    opposing
  • 00:05:37
    let's have an inhibitory
  • 00:05:38
    neurotransmitter and then that
  • 00:05:40
    neurotransmitter binds into this little
  • 00:05:42
    pocket on that ligand-gated ion channel
  • 00:05:44
    normally that channel has a valve that's
  • 00:05:46
    closing it like this
  • 00:05:47
    when the neurotransmitter binds it opens
  • 00:05:50
    up the valve if you will
  • 00:05:51
    and allows for negative ions to flow
  • 00:05:55
    into the cell these negative ions make
  • 00:05:57
    the inside of the cell
  • 00:05:59
    more negative than it usually is it
  • 00:06:01
    brings it below
  • 00:06:02
    what's called resting membrane potential
  • 00:06:05
    that's called
  • 00:06:06
    hyperpolarization and hyperpolarization
  • 00:06:08
    when you make the cell more negative
  • 00:06:10
    than it usually
  • 00:06:11
    is is called an ipsp
  • 00:06:14
    why is this important because these
  • 00:06:16
    terms collectively
  • 00:06:17
    are called are involved in what's called
  • 00:06:19
    your graded
  • 00:06:22
    potentials and these are basically
  • 00:06:24
    little
  • 00:06:25
    changes in the voltage of the cell
  • 00:06:28
    membrane
  • 00:06:28
    to basically try to get the cell to
  • 00:06:32
    develop
  • 00:06:32
    the ability to generate action
  • 00:06:34
    potentials so your dendrites are
  • 00:06:36
    involved in graded potentials that's
  • 00:06:39
    what i want you to know
  • 00:06:40
    how via these ligand-gated ion channels
  • 00:06:42
    there is another way though
  • 00:06:44
    and it's just important for you to
  • 00:06:45
    remember the second way
  • 00:06:47
    the second way that it has other
  • 00:06:49
    proteins here that are involved here
  • 00:06:51
    is via what's called g-protein-coupled
  • 00:06:54
    receptors
  • 00:06:56
    we're not going to go through this
  • 00:06:57
    mechanism because it's long and it's
  • 00:06:59
    unnecessary
  • 00:07:01
    we have other videos that cover that but
  • 00:07:02
    these have g protein couple receptors
  • 00:07:05
    that again imagine you have a neuron
  • 00:07:07
    here releases a neurotransmitter
  • 00:07:09
    that neurotransmitter binds onto this
  • 00:07:11
    little receptive region of this pocket
  • 00:07:13
    this jeep this uh
  • 00:07:15
    receptor here when it binds onto it
  • 00:07:17
    activates what's called a g
  • 00:07:18
    protein and that g protein can activate
  • 00:07:21
    what's called
  • 00:07:22
    second messengers and these can be a
  • 00:07:23
    bunch of different types
  • 00:07:25
    but eventually that activates what's
  • 00:07:26
    called protein kinases
  • 00:07:28
    right and the whole point here is that
  • 00:07:30
    these protein kinases
  • 00:07:32
    can go and phosphorylate particular
  • 00:07:35
    proteins that are present on the cell
  • 00:07:36
    membrane
  • 00:07:38
    and maybe this protein that's present on
  • 00:07:40
    the cell membrane
  • 00:07:41
    that's activated by these protein
  • 00:07:44
    kinases
  • 00:07:45
    right what that will do is that allow
  • 00:07:47
    for either positive ions to flow in
  • 00:07:49
    making a positive change bringing about
  • 00:07:52
    an epsp
  • 00:07:54
    or bringing in negative ions into the
  • 00:07:56
    cell
  • 00:07:57
    and if those negative ions flow into the
  • 00:07:58
    cell that could be causing a
  • 00:08:00
    ipsp so it's the same concept just a
  • 00:08:03
    different way that they get there
  • 00:08:05
    this is what dendrites do now
  • 00:08:08
    not only do dendrites perform this type
  • 00:08:10
    of action which are involved in graded
  • 00:08:12
    potentials whether it be ligand-gated
  • 00:08:14
    mediated
  • 00:08:15
    or g-protein-coupled mediated cell
  • 00:08:18
    bodies also do that
  • 00:08:19
    so that means if you were to take a look
  • 00:08:21
    and zoom in
  • 00:08:22
    on that cell body and really look at it
  • 00:08:25
    everything that's going to be happening
  • 00:08:27
    there
  • 00:08:27
    is happening here it's the same type of
  • 00:08:30
    activity
  • 00:08:30
    so you also will have neurons which are
  • 00:08:33
    going to be interacting here
  • 00:08:35
    presynaptic neurons interacting with the
  • 00:08:37
    cell body okay
  • 00:08:39
    so that's one thing so one thing we
  • 00:08:40
    already know is that this also this cell
  • 00:08:42
    body is involved in
  • 00:08:44
    graded potentials
  • 00:08:47
    but it has an even more significant
  • 00:08:49
    function
  • 00:08:50
    very important function it's involved in
  • 00:08:53
    protein
  • 00:08:56
    synthesis and when i talk about this
  • 00:08:58
    we'll go over
  • 00:08:59
    those literally the most basic
  • 00:09:02
    aspects of what i mean by protein
  • 00:09:05
    synthesis the process
  • 00:09:06
    but what i want you to know is when we
  • 00:09:08
    talk about protein synthesis
  • 00:09:11
    what type of proteins are we making
  • 00:09:13
    there's proteins all across this dang
  • 00:09:15
    cell
  • 00:09:15
    it could be neurotransmitters that
  • 00:09:17
    you're actually synthesizing
  • 00:09:19
    it could be enzymes that are involved in
  • 00:09:21
    particular cellular processes
  • 00:09:23
    it could be membrane proteins maybe
  • 00:09:26
    membrane proteins that are going to be
  • 00:09:28
    voltage-gated
  • 00:09:29
    ligand-gated or g-protein-coupled
  • 00:09:32
    receptors so it could be membrane
  • 00:09:34
    proteins
  • 00:09:36
    so it is important that this cell body
  • 00:09:38
    perform that function
  • 00:09:39
    how does all of that happen we're going
  • 00:09:41
    to briefly go through that
  • 00:09:43
    all right so when we talk about protein
  • 00:09:45
    synthesis how is all of this happening
  • 00:09:47
    we understand the process of how it's
  • 00:09:48
    involved in the graded potentials
  • 00:09:51
    which is basically designed to take
  • 00:09:52
    resting membrane potential to a
  • 00:09:53
    threshold potential to trigger an action
  • 00:09:55
    potential right we talked about that
  • 00:09:57
    but how is it involved in this protein
  • 00:09:58
    synthesis in the basic sense here
  • 00:10:00
    you have the dna inside the nucleus of
  • 00:10:02
    the cell body right
  • 00:10:04
    and that dna may have particular genes
  • 00:10:07
    that are constantly expressed and maybe
  • 00:10:10
    these proteins are for
  • 00:10:12
    voltage-gated proteins for the
  • 00:10:14
    ligand-gated maybe it's for
  • 00:10:16
    neurotransmitters enzymes whatever
  • 00:10:18
    but whenever that gene is transcribed
  • 00:10:22
    we convert that into mrna right that's
  • 00:10:26
    called transcription
  • 00:10:27
    that mrna is then done it does what it's
  • 00:10:30
    then exported out of the nucleus and
  • 00:10:31
    into the cytoplasm
  • 00:10:33
    and then comes to this next structure
  • 00:10:35
    here this next structure encounters is
  • 00:10:38
    called the rough endoplasmic reticulum
  • 00:10:40
    but it's important to remember that the
  • 00:10:42
    rough endoplasmic reticulum inside of
  • 00:10:43
    neurons
  • 00:10:44
    is sometimes referred to as nissl bodies
  • 00:10:47
    okay so sometimes you might hear the
  • 00:10:49
    term nissl
  • 00:10:51
    bodies and this is basically a
  • 00:10:53
    specialized name for the rough er in
  • 00:10:55
    neurons
  • 00:10:56
    now this mrna may go to this rough
  • 00:10:59
    endoplasmic reticulum
  • 00:11:00
    and at the rough endoplasmic reticulum
  • 00:11:03
    it'll use that mrna
  • 00:11:05
    and then translate it in other words
  • 00:11:07
    it's going to turn this
  • 00:11:08
    into a protein okay
  • 00:11:12
    so it's going to turn that into a
  • 00:11:13
    protein that protein will then be
  • 00:11:15
    packaged in the rough endoplasmic
  • 00:11:17
    reticulum and then
  • 00:11:18
    budded off to then be
  • 00:11:22
    modified and further packaged by what
  • 00:11:25
    else
  • 00:11:26
    by the golgi apparatus so then here's
  • 00:11:29
    you're going to be a little vesicle
  • 00:11:30
    coming off of the rough er
  • 00:11:32
    consisting of the proteins it'll then
  • 00:11:34
    move into the golgi apparatus
  • 00:11:36
    and in the golgi apparatus it'll undergo
  • 00:11:38
    modification and then packaging into
  • 00:11:41
    vesicles where we're going to take that
  • 00:11:42
    protein and package it
  • 00:11:45
    inside of this vesicle and then bud that
  • 00:11:48
    vesicle
  • 00:11:48
    off of what is this structure here this
  • 00:11:51
    structure is called your
  • 00:11:52
    golgi apparatus right so this is your
  • 00:11:54
    golgi
  • 00:11:57
    now from here when you bud that gold off
  • 00:12:00
    the golgi you budge that vesicle off
  • 00:12:02
    the bud that vesicle off which contains
  • 00:12:04
    in it proteins let's just pretend
  • 00:12:06
    that this protein that we're
  • 00:12:08
    synthesizing here is actually a
  • 00:12:10
    neurotransmitter
  • 00:12:12
    neurotransmitters that are packaged into
  • 00:12:14
    these vesicles have to be
  • 00:12:16
    transported down the axon to that axon
  • 00:12:19
    terminal
  • 00:12:20
    and we have to next we're going to talk
  • 00:12:22
    about how in the heck
  • 00:12:24
    do those vesicles containing proteins
  • 00:12:27
    and other things like organelles
  • 00:12:28
    get transported down the axon to the
  • 00:12:31
    axon terminal
  • 00:12:32
    so again we understand that this protein
  • 00:12:34
    synthesis process is what is occurring
  • 00:12:36
    in the nucleus and this may not just be
  • 00:12:38
    neurotransmitters
  • 00:12:40
    this could also be enzymes
  • 00:12:43
    or membrane proteins
  • 00:12:48
    okay that is what i want you to know
  • 00:12:52
    about the cell body okay now that we've
  • 00:12:54
    talked about that let's move on to the
  • 00:12:55
    next part which is the axon
  • 00:12:56
    so the axon this long tube between the
  • 00:12:59
    cell body and the axon terminal
  • 00:13:01
    what is its function obviously pretty
  • 00:13:03
    much anybody who's learning about this
  • 00:13:05
    knows that the primary function of the
  • 00:13:08
    axon
  • 00:13:08
    is to conduct action potentials and what
  • 00:13:12
    is an action potential
  • 00:13:14
    it's a voltage usually a positive
  • 00:13:18
    charge a flow of positive charge down
  • 00:13:21
    the axon from the cell body down the
  • 00:13:23
    axon to the axon terminal
  • 00:13:25
    right where there's a flow of positive
  • 00:13:28
    charge that's called the depolarization
  • 00:13:30
    but then following that is usually a
  • 00:13:33
    repolarizing wave
  • 00:13:35
    so when we talk about an action
  • 00:13:36
    potential there's the depolarization
  • 00:13:39
    wave and then there's the
  • 00:13:43
    re-polarization
  • 00:13:44
    wave and we'll go over that a little bit
  • 00:13:46
    later
  • 00:13:48
    and talk about what the heck that means
  • 00:13:50
    but that's the big thing we know about
  • 00:13:51
    the axon is it conducts
  • 00:13:52
    action potentials right depolarizing
  • 00:13:55
    wave down a positive charge followed by
  • 00:13:57
    a repolarizing wave of negative charge
  • 00:13:59
    the next part is the one that i actually
  • 00:14:01
    really want to talk about because it's
  • 00:14:02
    not often talked about but it's
  • 00:14:03
    clinically relevant
  • 00:14:06
    is you have this big old blue structure
  • 00:14:07
    in the middle that we're going to talk
  • 00:14:08
    about called microtubules
  • 00:14:10
    and on those microtubules are special
  • 00:14:12
    types of proteins called
  • 00:14:13
    motor proteins and these motor proteins
  • 00:14:16
    are involved in
  • 00:14:17
    transporting things up and down the axon
  • 00:14:20
    axonal transport so this purple
  • 00:14:24
    protein is actually referred to as
  • 00:14:26
    kinesin
  • 00:14:28
    and this kinesin is a what's called a
  • 00:14:30
    positive and directed motor protein
  • 00:14:32
    i don't really care about that what i
  • 00:14:33
    want you to know is that
  • 00:14:35
    it moves things we'll talk about what
  • 00:14:37
    those things those are
  • 00:14:38
    from the cell body down to the axon
  • 00:14:41
    terminal
  • 00:14:42
    so when you go cell body
  • 00:14:46
    to the axon terminal
  • 00:14:49
    that is referred to as
  • 00:14:53
    anterograde
  • 00:14:56
    axonal transport
  • 00:14:59
    to give you an idea of what kind of
  • 00:15:01
    things this would be transporting we
  • 00:15:02
    already talked about it
  • 00:15:04
    this vesicle containing
  • 00:15:05
    neurotransmitters membrane proteins
  • 00:15:07
    enzymes
  • 00:15:07
    i might have to transport that down to
  • 00:15:09
    the axon terminal so i can release it
  • 00:15:11
    or i can plug it into the membrane down
  • 00:15:13
    here or maybe i've got to take a
  • 00:15:14
    mitochondria down here because i need a
  • 00:15:16
    lot of atp to be produced down here
  • 00:15:18
    to drive some of these processes so it's
  • 00:15:20
    moving
  • 00:15:21
    organelles neurotransmitters and
  • 00:15:22
    vesicles down
  • 00:15:24
    in the the opposite situation you need
  • 00:15:27
    this little dude
  • 00:15:28
    or dudette to be taking things in the
  • 00:15:30
    opposite direction
  • 00:15:31
    so this orange protein is called
  • 00:15:34
    dynein and dynein is a minus indirected
  • 00:15:39
    motor protein
  • 00:15:40
    and this is taking things from the axon
  • 00:15:42
    terminal
  • 00:15:44
    and again it could be an axon i'm just
  • 00:15:46
    giving you the direction going from axon
  • 00:15:48
    terminal towards the
  • 00:15:50
    cell body and this when you're going in
  • 00:15:54
    that direction
  • 00:15:55
    is called retrograde
  • 00:15:59
    axonal transport
  • 00:16:02
    what kind of things would you want to be
  • 00:16:04
    transporting then
  • 00:16:06
    maybe the mitochondria has lived its
  • 00:16:08
    fine life and it's time for it to go
  • 00:16:10
    okay and it needs to be taken up and
  • 00:16:12
    either recycled or
  • 00:16:13
    or degraded maybe you want to bring up
  • 00:16:16
    some growth factors
  • 00:16:17
    up to the cell body to where the nucleus
  • 00:16:19
    is to stimulate
  • 00:16:21
    proteins that are involved there we
  • 00:16:23
    might need that
  • 00:16:24
    so that's what i want to now talk about
  • 00:16:26
    is some of those things that it carries
  • 00:16:28
    to and from and how it's clinically
  • 00:16:30
    relevant
  • 00:16:31
    all right so what do we say the axon
  • 00:16:33
    does it conducts action potentials
  • 00:16:35
    which we said if we're going down there
  • 00:16:36
    could be a positive flow of charge down
  • 00:16:38
    the axon
  • 00:16:39
    followed by a negative charge or a
  • 00:16:41
    depolarizing wave followed by a
  • 00:16:42
    repolarizing wave i want to briefly talk
  • 00:16:44
    about that
  • 00:16:45
    we're going to talk about it more in the
  • 00:16:46
    video on resting graded and action
  • 00:16:48
    potentials but
  • 00:16:50
    here on this cell membrane of these
  • 00:16:52
    purple channels and let's refer to these
  • 00:16:53
    channels that are on here as these
  • 00:16:55
    voltage
  • 00:16:56
    gated sodium channels
  • 00:17:00
    and these guys will open once you hit a
  • 00:17:03
    particular
  • 00:17:04
    voltage a threshold voltage if you will
  • 00:17:07
    once you hit that threshold voltage the
  • 00:17:09
    sodium ions will then rush
  • 00:17:11
    into this axon and when these positive
  • 00:17:14
    ions rush
  • 00:17:15
    into the axon the cell the actual
  • 00:17:18
    cytoplasm here
  • 00:17:19
    it really makes the inside of the cell
  • 00:17:21
    super positive
  • 00:17:23
    and you want to think about this is that
  • 00:17:24
    you have a flow of positive charges
  • 00:17:27
    that are moving down this axon
  • 00:17:31
    and that is where that depolarizing or
  • 00:17:33
    flow of positive charges are coming from
  • 00:17:35
    that's involved in the depolarizing
  • 00:17:37
    phase of the action potential
  • 00:17:40
    on the other hand you want the action
  • 00:17:43
    potential after you've stimulated the
  • 00:17:45
    axon in the terminal
  • 00:17:46
    you need to now relax or cause this
  • 00:17:49
    cell to go into a resting state after
  • 00:17:52
    it's been depolarized so you need a
  • 00:17:54
    negative charge to flow across
  • 00:17:55
    so that the cell can rest in order to do
  • 00:17:58
    that you need these maroon
  • 00:18:00
    channels which are called your voltage
  • 00:18:04
    gated potassium channels and these are
  • 00:18:07
    only going to be open when you hit a
  • 00:18:09
    particular threshold
  • 00:18:11
    usually after depolarization once they
  • 00:18:13
    open potassium floods out of the cell
  • 00:18:16
    when potassium floods out of the cell
  • 00:18:18
    what does that do
  • 00:18:20
    it causes the inside of the cell to
  • 00:18:22
    become extra negative
  • 00:18:24
    and now that negative charge if you're
  • 00:18:27
    kind of skipping along here step by step
  • 00:18:29
    by step
  • 00:18:29
    that negative charge is flowing down the
  • 00:18:32
    axon to the axon terminal
  • 00:18:34
    and this is called the repolarizing wave
  • 00:18:36
    so that's the involvement of the axon
  • 00:18:39
    the next thing is this transport process
  • 00:18:41
    here is your kinesin protein right so
  • 00:18:43
    here's the kinesis we'll put a k right
  • 00:18:44
    here in his body
  • 00:18:46
    what is he transporting down here well
  • 00:18:48
    imagine he's transporting what that
  • 00:18:50
    vesicle
  • 00:18:51
    and what kind of vesicle that vesicle
  • 00:18:53
    that's containing
  • 00:18:55
    multiple things proteins in general
  • 00:18:57
    right and maybe inside of this it's
  • 00:18:58
    containing neurotransmitters
  • 00:19:00
    membrane proteins enzymes that we need
  • 00:19:03
    down here
  • 00:19:04
    maybe it's also transporting
  • 00:19:06
    mitochondria because you need
  • 00:19:07
    mitochondria down there as well so maybe
  • 00:19:10
    it's also
  • 00:19:11
    transporting a mitochondria down to the
  • 00:19:14
    axon terminal
  • 00:19:16
    in the opposite situation think about
  • 00:19:18
    this this guy
  • 00:19:19
    right this is your dynein this is going
  • 00:19:21
    to be transporting
  • 00:19:23
    certain types of things back up here
  • 00:19:25
    what kind of things is it going to be
  • 00:19:26
    transporting
  • 00:19:28
    back up here maybe it's transporting any
  • 00:19:30
    vesicles
  • 00:19:32
    or mitochondria that have lived their
  • 00:19:35
    best
  • 00:19:36
    life but it's time for them to go
  • 00:19:39
    and in that situation we could be
  • 00:19:41
    transporting up
  • 00:19:43
    vesicles that contain that need to be
  • 00:19:45
    degraded or organelles that need to be
  • 00:19:47
    degraded
  • 00:19:48
    or recycled the last situation is it
  • 00:19:51
    could be carrying up something very very
  • 00:19:53
    important that i need you guys to
  • 00:19:54
    remember
  • 00:19:56
    we're going to do this in orange so you
  • 00:19:58
    don't forget it
  • 00:20:00
    it could be carrying upwards let's say
  • 00:20:02
    that for some reason there was some
  • 00:20:04
    nerve injury
  • 00:20:05
    or there's some damage to the nerve
  • 00:20:06
    terminal or the axon itself
  • 00:20:10
    and you want to tell the cell body that
  • 00:20:13
    maybe there was some damage to the
  • 00:20:14
    membrane some damage to some of the
  • 00:20:16
    proteins or something like that down
  • 00:20:17
    here
  • 00:20:18
    so what this axon terminal will do is
  • 00:20:20
    it'll send up
  • 00:20:21
    through these dynein proteins nerve
  • 00:20:24
    growth factors and this nerve growth
  • 00:20:27
    factor as it's transported by the
  • 00:20:29
    dyneins up here what can it do
  • 00:20:31
    it can then go up to the
  • 00:20:34
    cell body in the nucleus and this nerve
  • 00:20:37
    growth factor
  • 00:20:38
    may stimulate particular genes to
  • 00:20:41
    increase the expression of mrna increase
  • 00:20:44
    the translation of the mrna
  • 00:20:46
    and increase the packaging and
  • 00:20:48
    production of proteins
  • 00:20:49
    in vesicles so that we can transport
  • 00:20:52
    down here
  • 00:20:53
    more vesicles containing more proteins
  • 00:20:55
    or other different organelles
  • 00:20:57
    to help to repair or grow whatever's
  • 00:21:00
    going on down here at the axon terminal
  • 00:21:02
    or distal axon
  • 00:21:03
    isn't that cool i think it is
  • 00:21:07
    the last thing that i need you guys to
  • 00:21:09
    know here
  • 00:21:10
    is that pathogens love to plague these
  • 00:21:12
    axonal transports
  • 00:21:14
    you know there's a virus called the
  • 00:21:16
    polio virus
  • 00:21:19
    or your rabies virus
  • 00:21:22
    or your herpes simplex virus or your
  • 00:21:25
    varicella zoster virus all of these
  • 00:21:27
    viruses
  • 00:21:28
    they can basically infect your nerve
  • 00:21:30
    terminals
  • 00:21:32
    from the nerve terminals they're going
  • 00:21:35
    to try to migrate up to the cell body
  • 00:21:36
    because these are viruses they need our
  • 00:21:38
    nuclear machinery
  • 00:21:39
    to generate more viral proteins and
  • 00:21:41
    replicate they can't do that down here
  • 00:21:43
    when they infect the nerve terminal
  • 00:21:45
    so what they do is is they hitch a ride
  • 00:21:48
    with these motor proteins
  • 00:21:49
    these dyneins and then they travel
  • 00:21:52
    upwards towards the cell body
  • 00:21:56
    and then this virus if you will can then
  • 00:21:59
    use
  • 00:22:01
    our nuclear machinery to make more
  • 00:22:03
    viruses
  • 00:22:05
    destroying this neuron you know in a
  • 00:22:07
    perfect example of it going the opposite
  • 00:22:09
    direction
  • 00:22:10
    you know when someone ever gets um
  • 00:22:12
    shingles
  • 00:22:13
    right if they get like the virus the
  • 00:22:14
    varicella zoster virus
  • 00:22:16
    they get infected that virus travels up
  • 00:22:18
    here
  • 00:22:19
    uses the nuclear machinery but maybe it
  • 00:22:21
    lays dormant for a couple years
  • 00:22:24
    then from some stress immunosuppressive
  • 00:22:26
    issue
  • 00:22:27
    that virus gets activated and then it
  • 00:22:30
    starts producing tons of viral particles
  • 00:22:32
    and then it uses the kinesin protein
  • 00:22:36
    to bring that virus back down to the
  • 00:22:38
    axon terminal
  • 00:22:40
    and then from the axon terminal it gets
  • 00:22:42
    released out to the skin
  • 00:22:43
    tissue and what happens it starts
  • 00:22:45
    damaging the skin tissue
  • 00:22:46
    and you can end up with shingles so do
  • 00:22:49
    you see how pathogens can really
  • 00:22:51
    kind of use this axonal transport
  • 00:22:53
    mechanism to their advantage in a way
  • 00:22:55
    all right so that's why i wanted us to
  • 00:22:57
    know that all right let's talk about the
  • 00:22:58
    axon terminal
  • 00:23:00
    all right so the next thing that we have
  • 00:23:01
    to talk about is the axon terminal the
  • 00:23:03
    axon terminal i just want you to
  • 00:23:05
    remember that this is the secretory
  • 00:23:07
    region
  • 00:23:08
    what in the heck does that mean that
  • 00:23:11
    this is where
  • 00:23:12
    neurotransmitters are released
  • 00:23:16
    also not only is it the area where
  • 00:23:18
    neurotransmitters are released
  • 00:23:20
    it is also very very important where
  • 00:23:23
    there is the
  • 00:23:24
    re-uptake of
  • 00:23:27
    neurotransmitters that are involved here
  • 00:23:29
    i can't stress that enough
  • 00:23:31
    the re-uptake of particular
  • 00:23:32
    neurotransmitters will apply a very
  • 00:23:34
    quick clinical
  • 00:23:35
    relevance to that but now let's talk
  • 00:23:37
    about how it's involved in the secretory
  • 00:23:39
    region how it's involved in this
  • 00:23:40
    neurotransmitter release
  • 00:23:41
    and then how it's involved in reuptake
  • 00:23:42
    and talk about a quick clinical
  • 00:23:44
    relevance to that so this depolarizing
  • 00:23:47
    wave of action potentials because of
  • 00:23:48
    this
  • 00:23:50
    voltage-gated sodium channels that are
  • 00:23:51
    allowing for sodium to rush in and move
  • 00:23:53
    down the axon
  • 00:23:54
    to the axon terminal that voltage
  • 00:23:57
    stimulates these voltage-gated calcium
  • 00:23:59
    channels
  • 00:24:00
    so this is going to be your
  • 00:24:00
    voltage-gated calcium channels
  • 00:24:04
    now what happens
  • 00:24:07
    is once this is stimulated calcium will
  • 00:24:10
    rush
  • 00:24:10
    into this axon terminal when calcium
  • 00:24:14
    rushes into the axon terminal there's a
  • 00:24:15
    very significant reason
  • 00:24:17
    you know what's on these vesicles that
  • 00:24:18
    we talked about which were consisting of
  • 00:24:20
    what
  • 00:24:21
    neurotransmitters in there right
  • 00:24:24
    consisting within the vesicle they have
  • 00:24:26
    particular proteins that are
  • 00:24:28
    embedded on their vesicular membrane and
  • 00:24:31
    on the plasma membrane of this axon
  • 00:24:33
    terminal
  • 00:24:34
    these are called snare proteins the
  • 00:24:36
    snare protein that's present here
  • 00:24:38
    on the vesicle are called v snares
  • 00:24:42
    and if you truly want to know it they're
  • 00:24:44
    called synaptobrevin
  • 00:24:46
    and synaptotagmin the other one here on
  • 00:24:49
    the actual cell
  • 00:24:50
    membrane of the axon terminal is called
  • 00:24:51
    your t snares
  • 00:24:54
    and this is consisting of syntaxin and
  • 00:24:56
    snap25 if you truly want to know that
  • 00:24:59
    but what happens is is that calcium is
  • 00:25:02
    the bridge between the v
  • 00:25:04
    snares and the t snare so once it comes
  • 00:25:06
    in it binds to these little
  • 00:25:08
    v snares and t snares and acts as a
  • 00:25:10
    liquid linkage
  • 00:25:12
    and pulls the vesicle to the cell
  • 00:25:14
    membrane
  • 00:25:15
    and fuses the vesicular membrane with
  • 00:25:17
    the plasma membrane of the terminal
  • 00:25:19
    and what does that look like afterwards
  • 00:25:21
    look at this look at how cool this is
  • 00:25:23
    fuses with it and it looks like this
  • 00:25:27
    once that happens now all of these
  • 00:25:29
    neurotransmitters which are located in
  • 00:25:31
    the vesicle are now
  • 00:25:32
    open to be released out in the synapse
  • 00:25:35
    and maybe out in the synapse
  • 00:25:36
    is another neuron right maybe there's
  • 00:25:39
    another neuron out here and it has
  • 00:25:41
    particular receptors present on that
  • 00:25:43
    cell membrane
  • 00:25:45
    that that neurotransmitter will go and
  • 00:25:47
    bind to
  • 00:25:49
    and carry out maybe the same process
  • 00:25:50
    we've talked about to this point
  • 00:25:52
    here's the important point once that
  • 00:25:54
    neurotransmitter has exerted
  • 00:25:56
    its effect on this other cell whether
  • 00:25:58
    that be another neuron
  • 00:25:59
    another muscle whatever that
  • 00:26:01
    neurotransmitter has to be degraded
  • 00:26:04
    or taken out of that synapse and there's
  • 00:26:08
    two main ways that you remove
  • 00:26:10
    neurotransmitters from a synapse
  • 00:26:12
    so neurotransmitter termination if you
  • 00:26:15
    will
  • 00:26:17
    is done by two ways i consider here
  • 00:26:20
    one is by re-uptake
  • 00:26:24
    and the other one is by degradation so
  • 00:26:26
    you have an enzyme
  • 00:26:27
    sitting in the synapse that degrades
  • 00:26:30
    that neurotransmitter
  • 00:26:31
    the one that's really pertinent here
  • 00:26:33
    that you guys need to know
  • 00:26:36
    is this reuptake because that's where
  • 00:26:38
    the axon terminal comes in
  • 00:26:40
    let's say that neurotransmitter after it
  • 00:26:41
    binds with this receptor it does its
  • 00:26:43
    function
  • 00:26:44
    then what happens is we have to get that
  • 00:26:47
    neurotransmitter back into this
  • 00:26:49
    axon terminal to incorporate it back
  • 00:26:52
    into this vesicle
  • 00:26:53
    how do we do that we use this reuptake
  • 00:26:56
    protein
  • 00:26:56
    so you use a re-uptake protein present
  • 00:26:59
    here
  • 00:27:00
    to move that neurotransmitter
  • 00:27:03
    back in to the axon terminal
  • 00:27:07
    and then maybe from there maybe it has
  • 00:27:08
    to go undergo a couple enzymatic steps
  • 00:27:11
    but either way it'll get put back into
  • 00:27:13
    the vesicle
  • 00:27:14
    and recycled that's important why is
  • 00:27:17
    that important
  • 00:27:19
    let's say this neurotransmitter is
  • 00:27:21
    serotonin sometimes it's
  • 00:27:22
    written as 5-hydroxytryptamine 5-ht
  • 00:27:27
    the reuptake protein would be called a
  • 00:27:29
    serotonin
  • 00:27:30
    reuptake protein if you give a drug
  • 00:27:34
    called s s r eyes
  • 00:27:38
    selective serotonin reuptake inhibitors
  • 00:27:41
    like
  • 00:27:41
    zoloft lexapro all of those things uh
  • 00:27:46
    prozac those are going to inhibit
  • 00:27:49
    these reuptake proteins why is that
  • 00:27:51
    important
  • 00:27:52
    now that neurotransmitter can't be
  • 00:27:54
    brought back into this actual axon
  • 00:27:56
    terminal
  • 00:27:56
    and it sits out in this synapse
  • 00:27:58
    continuously stimulating this cell
  • 00:28:00
    that could be important whenever that
  • 00:28:03
    excess 5-hydroxytryptamine is needed to
  • 00:28:05
    improve
  • 00:28:06
    mood in people with depression anxiety
  • 00:28:08
    obsessive-compulsive disorders
  • 00:28:10
    so that's why this is so important that
  • 00:28:12
    you know sometimes the basic
  • 00:28:13
    functions of these components of the
  • 00:28:15
    neuron all right that covers axon
  • 00:28:16
    terminal
  • 00:28:17
    all right so we talked about the basic
  • 00:28:19
    structure and functions of the different
  • 00:28:20
    parts of the neuron now what we have to
  • 00:28:22
    remember is that when we talk about
  • 00:28:23
    neurons
  • 00:28:24
    and we might use a lot of this
  • 00:28:25
    terminology throughout the process of
  • 00:28:27
    all the neurology
  • 00:28:28
    videos in our playlist is that you have
  • 00:28:31
    to know how the neurons are classified
  • 00:28:33
    less commonly they're used in a
  • 00:28:35
    structural classification more commonly
  • 00:28:37
    especially throughout the process of all
  • 00:28:38
    the videos that
  • 00:28:39
    you guys are going to watch it's going
  • 00:28:40
    to be more functional classification
  • 00:28:42
    that we're going to talk about
  • 00:28:44
    so to get this part out of the way
  • 00:28:46
    because it is a little boring i'm not
  • 00:28:47
    going to lie to you
  • 00:28:48
    let's just talk about what these things
  • 00:28:49
    are and where you can find them so the
  • 00:28:51
    first one here is this multipolar neuron
  • 00:28:54
    so let's just write these out this is
  • 00:28:55
    your multi-polar neuron
  • 00:28:58
    and i'll explain why in a second this
  • 00:28:59
    one here is called your bipolar neuron
  • 00:29:03
    okay this is called your bipolar knot
  • 00:29:04
    and this last one over here
  • 00:29:06
    is called your pseudo unipolar neuron
  • 00:29:12
    and i'll explain why all of this and
  • 00:29:13
    then we'll talk about where you can find
  • 00:29:14
    them and why that
  • 00:29:15
    why you'd be finding them there so the
  • 00:29:17
    multipolar neurons the reason they're
  • 00:29:19
    called that it's very simple
  • 00:29:21
    look at how many dendritic extensions i
  • 00:29:22
    have coming off if i have three
  • 00:29:25
    plus dendritic extensions coming off
  • 00:29:26
    that's enough for me to call this a
  • 00:29:28
    multipolar neuron
  • 00:29:29
    multiple dendritic extensions with a
  • 00:29:31
    cell body and an axon extension that's a
  • 00:29:33
    multipolar
  • 00:29:34
    if i only see one dendritic extension
  • 00:29:38
    so one dendritic extension we'll put de
  • 00:29:41
    and one axon coming from the cell body
  • 00:29:43
    that's a bipolar neuron
  • 00:29:45
    it's not hard right pseudo-unipolar is
  • 00:29:48
    really
  • 00:29:48
    weird it doesn't really have a dendrite
  • 00:29:51
    and it doesn't really have like a
  • 00:29:52
    distinguishable
  • 00:29:54
    axon with a terminal kind of thing it
  • 00:29:56
    has here
  • 00:29:57
    your peripheral process so here's the
  • 00:29:59
    cell body
  • 00:30:01
    okay here's the cell body of it then you
  • 00:30:04
    have this process coming from the cell
  • 00:30:06
    body
  • 00:30:06
    usually out to your periphery so we call
  • 00:30:09
    this the peripheral
  • 00:30:12
    process and then this
  • 00:30:16
    part from the cell body going towards
  • 00:30:18
    the central nervous system
  • 00:30:20
    we call this part the central
  • 00:30:23
    process so pretty straightforward
  • 00:30:27
    okay now the important thing is to know
  • 00:30:29
    where you can find these things and
  • 00:30:31
    why you would generally find them there
  • 00:30:33
    for the most part
  • 00:30:34
    multipolar neurons think about it they
  • 00:30:36
    have tons of dendrites what does that
  • 00:30:37
    mean what does dendrites do
  • 00:30:39
    they're the receptive region so they
  • 00:30:41
    have to receive signals from multiple
  • 00:30:42
    neurons all over the
  • 00:30:44
    place think about the primary motor
  • 00:30:46
    cortex who does he have to receive
  • 00:30:48
    information from because that's an
  • 00:30:49
    example of a multipolar neuron
  • 00:30:51
    he would have to receive information
  • 00:30:53
    from your basal ganglia your basal
  • 00:30:56
    ganglia
  • 00:30:56
    they have to send information to your
  • 00:30:58
    motor cortex you know your sensory
  • 00:31:00
    cortex
  • 00:31:01
    it has to send information to the motor
  • 00:31:02
    cortex you know your cerebellum
  • 00:31:05
    it has to send information to your motor
  • 00:31:07
    cortex what else would send information
  • 00:31:10
    there
  • 00:31:10
    you also have other motor areas which
  • 00:31:12
    called your pre-motor cortex and your
  • 00:31:14
    supplementary motor cortex would have to
  • 00:31:15
    send information there
  • 00:31:16
    so it has to have all these receptive
  • 00:31:18
    regions and then
  • 00:31:20
    have a axon that goes down to your
  • 00:31:23
    spinal cord
  • 00:31:24
    that's an example of a multipolar neuron
  • 00:31:26
    multiple receptive regions with an axon
  • 00:31:28
    going down
  • 00:31:30
    same thing this is literally the same
  • 00:31:31
    concept your cerebellum
  • 00:31:33
    so obviously if we were to give an
  • 00:31:34
    example here just pick motor cortex
  • 00:31:38
    as one example the second example
  • 00:31:42
    pick your cerebellum and if we're really
  • 00:31:45
    being specific about what type of
  • 00:31:47
    neurons they actually give these neurons
  • 00:31:48
    in the motor cortex they call them
  • 00:31:50
    pyramidal cells and those cerebellum we
  • 00:31:52
    call them
  • 00:31:53
    purkinje cells if you truly want to know
  • 00:31:55
    that
  • 00:31:56
    i want you to get the basic concept
  • 00:31:57
    though where is the information multiple
  • 00:31:59
    receptive regions
  • 00:32:01
    your spinal cord picking up sensations
  • 00:32:03
    proprioceptive sensation
  • 00:32:05
    picking up information about your
  • 00:32:07
    equilibrium from your inner ear
  • 00:32:10
    picking up information from your motor
  • 00:32:12
    cortex about the particular
  • 00:32:14
    motor plan that you have to move all of
  • 00:32:16
    that has to go to the cerebellum
  • 00:32:18
    and then the cerebellum from there can
  • 00:32:19
    send its information to tons of
  • 00:32:21
    different areas
  • 00:32:22
    but you see how there's multiple
  • 00:32:23
    receptive regions and then an axon
  • 00:32:25
    extension
  • 00:32:26
    that's an example of multipolar neurons
  • 00:32:29
    bipolar neurons are really weird and you
  • 00:32:31
    find these mainly in your special
  • 00:32:33
    sensory organs which ones the retina
  • 00:32:37
    has bipolar neurons we talk about
  • 00:32:40
    really where like what they do because
  • 00:32:42
    these don't really generate action
  • 00:32:43
    potentials they generate what's called
  • 00:32:44
    graded potentials
  • 00:32:45
    we talk about that in our special
  • 00:32:46
    sensors special senses playlist
  • 00:32:49
    the other one is your olfactory
  • 00:32:51
    epithelium which are present in the the
  • 00:32:53
    roof
  • 00:32:54
    of the nasal cavity so the uh also the
  • 00:32:57
    ol
  • 00:32:58
    factory nerves
  • 00:33:02
    they're also examples of bipolar neurons
  • 00:33:04
    and then one more
  • 00:33:06
    is your inner ear particularly
  • 00:33:09
    like the vestibule and the semicircular
  • 00:33:11
    canals
  • 00:33:12
    are also example of bipolar neurons
  • 00:33:16
    so best way to remember this is mainly
  • 00:33:17
    your special sensory organs is really
  • 00:33:20
    where you'll find
  • 00:33:21
    bipolar neurons the last one is your
  • 00:33:24
    pseudo unipolar your pseudo unipolar is
  • 00:33:26
    actually very important i really want
  • 00:33:27
    you to remember this one
  • 00:33:30
    the main area where you're going to hear
  • 00:33:32
    them tons and tons and tons of times
  • 00:33:33
    throughout the neurology playlist
  • 00:33:35
    is your dorsal root ganglion your dorsal
  • 00:33:38
    root ganglion which is located
  • 00:33:41
    outside of your spinal cord so here is
  • 00:33:44
    going to be what's called the cell body
  • 00:33:45
    that part there
  • 00:33:47
    it has a peripheral process we said
  • 00:33:50
    right
  • 00:33:51
    that peripheral process may be going to
  • 00:33:54
    the skin let's just put here skin we're
  • 00:33:56
    just going to write skin
  • 00:33:57
    picking up sensations from the skin
  • 00:33:59
    taking it down this peripheral process
  • 00:34:02
    to where the cell body is then into the
  • 00:34:04
    central process and from here it may
  • 00:34:06
    synapse somewhere in your
  • 00:34:08
    spinal cord or go up to your brain okay
  • 00:34:12
    so this is an example of the
  • 00:34:15
    pseudo-unipolar neuron but it's located
  • 00:34:17
    outside of the peripheral nerve outside
  • 00:34:19
    of the central nervous system
  • 00:34:21
    and a bunch of cell bodies located
  • 00:34:24
    outside of the peripheral nervous system
  • 00:34:26
    are called a ganglia and since it's near
  • 00:34:28
    the dorsal
  • 00:34:30
    root that's why we call it a dorsal root
  • 00:34:32
    ganglia
  • 00:34:33
    all right beautiful last but not least
  • 00:34:37
    is certain cranial nerves have
  • 00:34:39
    pseudo-unipolar neurons
  • 00:34:41
    classical example classical is cranial
  • 00:34:44
    nerve
  • 00:34:45
    five the cranial nerve five tried
  • 00:34:48
    which is your trigeminal nerve your
  • 00:34:50
    trigeminal
  • 00:34:52
    ganglion this is a
  • 00:34:56
    perfect example you know there's a
  • 00:34:58
    ganglia that sits here inside kind of
  • 00:35:00
    like outside within the skull base here
  • 00:35:02
    and it has three divisions one is called
  • 00:35:04
    a ophthalmic division
  • 00:35:06
    a maxillary division and a mandibular
  • 00:35:08
    division right
  • 00:35:09
    but they're picking up sensations all
  • 00:35:11
    from the face
  • 00:35:12
    those sensations travel down their
  • 00:35:14
    peripheral processes
  • 00:35:16
    to the cell body from the cell body you
  • 00:35:19
    have a central process that goes into
  • 00:35:20
    the central nervous system
  • 00:35:22
    to the nucleus inside of your brainstem
  • 00:35:24
    which is your trigeminal nucleus
  • 00:35:26
    that's another example of a
  • 00:35:28
    pseudo-unipolar neuron all right
  • 00:35:29
    beautiful
  • 00:35:30
    that's the structural classification
  • 00:35:32
    let's hit the functional more important
  • 00:35:33
    one
  • 00:35:34
    all right so we talked about the
  • 00:35:35
    structural classification of neurons now
  • 00:35:36
    let's talk about the one that you're
  • 00:35:38
    probably going to hear a lot of
  • 00:35:39
    throughout the process of our neurology
  • 00:35:41
    lectures which is the functional
  • 00:35:42
    classification
  • 00:35:43
    so when we talk about neurons they can
  • 00:35:44
    be sensory neurons
  • 00:35:46
    motor neurons or interneurons now what
  • 00:35:48
    the heck does that mean
  • 00:35:49
    i want to establish some terminology
  • 00:35:51
    here so
  • 00:35:53
    sensations it can pick up sensations
  • 00:35:55
    from your viscera
  • 00:35:56
    maybe sensations from the lungs from the
  • 00:35:59
    heart from the git from the urogenital
  • 00:36:01
    tract
  • 00:36:02
    those visceral sensations are going from
  • 00:36:05
    these organs
  • 00:36:06
    to your actual central nervous system in
  • 00:36:08
    this case the
  • 00:36:09
    brain or the spinal cord so that's
  • 00:36:11
    called afferent information so sensory
  • 00:36:14
    information is also referred to as
  • 00:36:16
    afferent
  • 00:36:18
    information so you can have neurons that
  • 00:36:19
    are taking sensory information or
  • 00:36:20
    afferent information
  • 00:36:22
    to your cns but since this is coming
  • 00:36:24
    from the viscera
  • 00:36:26
    we give this a special term which is
  • 00:36:28
    called general
  • 00:36:29
    visceral afferent neurons this is terms
  • 00:36:33
    that will come up later in the lectures
  • 00:36:34
    okay
  • 00:36:35
    it's important to know that one the next
  • 00:36:38
    one is you could be picking up
  • 00:36:39
    sensations
  • 00:36:40
    from your skin or from your skeletal
  • 00:36:43
    muscles
  • 00:36:44
    or from your joints your ligaments all
  • 00:36:47
    of those
  • 00:36:47
    areas this is somatic sensation so when
  • 00:36:50
    it's somatic meaning it's coming from
  • 00:36:52
    skin
  • 00:36:52
    muscle joints when i mean muscle i mean
  • 00:36:55
    skeletal muscle
  • 00:36:56
    okay joints ligaments that sensory
  • 00:36:59
    information can be taken to your brain
  • 00:37:01
    or spinal cord
  • 00:37:02
    but that is called general somatic
  • 00:37:06
    afferent fibers okay
  • 00:37:09
    next one you could be having sensory
  • 00:37:11
    information being conducted from your
  • 00:37:14
    special sensory organs which are going
  • 00:37:16
    to be responsible for
  • 00:37:17
    vision and hearing if this
  • 00:37:21
    is traveling towards your actual central
  • 00:37:23
    nervous system and it's coming from a
  • 00:37:24
    special sensory organ
  • 00:37:26
    very particular here from the eyes or
  • 00:37:29
    ears
  • 00:37:29
    this is called special sensory afferent
  • 00:37:32
    fibers
  • 00:37:33
    ssa fibers okay
  • 00:37:37
    last but not least if the sensations
  • 00:37:39
    that are being
  • 00:37:40
    taken to your central nervous system
  • 00:37:42
    affair and information through these
  • 00:37:44
    sensory neurons
  • 00:37:45
    are coming from your smell or from taste
  • 00:37:49
    and going to your central nervous system
  • 00:37:51
    that is a special sense
  • 00:37:52
    but it's more visceral so it's called
  • 00:37:55
    special
  • 00:37:56
    visceral afferent neurons
  • 00:37:59
    so these are terms that i want you to
  • 00:38:01
    understand whenever they come up in
  • 00:38:03
    future lectures
  • 00:38:05
    all right the next one is the motor
  • 00:38:08
    neurons
  • 00:38:09
    motor neurons are taking efferent
  • 00:38:12
    information that means they're going
  • 00:38:13
    away from the central nervous system
  • 00:38:16
    and going to the effector organ here
  • 00:38:19
    in this case it could be going to
  • 00:38:22
    your visceral organs maybe it's going to
  • 00:38:26
    the smooth muscle within the respiratory
  • 00:38:27
    bronchi
  • 00:38:28
    maybe it's going to the cardiac muscle
  • 00:38:30
    within the heart maybe it's going to
  • 00:38:32
    glance
  • 00:38:33
    which are going to be present all in
  • 00:38:35
    different places
  • 00:38:37
    that type of information is autonomic
  • 00:38:39
    information
  • 00:38:40
    but it's visceral and it's motor and
  • 00:38:43
    it's going away from the central nervous
  • 00:38:46
    system
  • 00:38:46
    so these fibers that are going to be
  • 00:38:48
    motor fibers from central nervous system
  • 00:38:50
    to viscera
  • 00:38:51
    for smooth muscle cardiac muscle and
  • 00:38:53
    gland activity is called
  • 00:38:55
    general visceral efferent neurons
  • 00:39:00
    the motor neurons that are going from
  • 00:39:01
    the central nervous system
  • 00:39:03
    away towards the effector organ in this
  • 00:39:05
    case
  • 00:39:06
    skeletal muscle right skeletal muscle
  • 00:39:10
    this is somatic function so this is
  • 00:39:12
    called
  • 00:39:13
    general somatic efferent
  • 00:39:16
    neurons which are taking motor
  • 00:39:18
    information from the central nervous
  • 00:39:19
    system to skeletal muscles
  • 00:39:22
    last but not least the ridiculous ones
  • 00:39:24
    here they love to give extra names to
  • 00:39:26
    make everything complicated for us
  • 00:39:28
    but there's going to be nerves that go
  • 00:39:31
    to special muscles
  • 00:39:32
    around the head and neck area that are
  • 00:39:35
    carried
  • 00:39:35
    by a couple different nerves cranial
  • 00:39:37
    nerve 5 which is your trigeminal nerve
  • 00:39:40
    cranial nerve seven which is your facial
  • 00:39:43
    nerve
  • 00:39:44
    cranial nerve nine which is your
  • 00:39:46
    glossopharyngeal nerve
  • 00:39:48
    and cranial nerve 10 which is your vagus
  • 00:39:50
    nerve
  • 00:39:51
    these will supply muscles
  • 00:39:54
    of the head and neck region from a
  • 00:39:57
    particular
  • 00:39:58
    embryological uh thing called your
  • 00:40:01
    pharyngeal arches
  • 00:40:03
    and really the best way to remember them
  • 00:40:05
    is correlating with the nerve
  • 00:40:07
    so cranial nerve five supplies the first
  • 00:40:09
    pharyngeal arch
  • 00:40:10
    cranial nerve seven plus supplies the
  • 00:40:12
    second pharyngeal arch
  • 00:40:13
    glossopharyngeal supplies the third
  • 00:40:15
    pharyngeal arch
  • 00:40:17
    and then the vagus supplies the fourth
  • 00:40:20
    and the sixth sixth
  • 00:40:23
    pharyngeal arch and again these are
  • 00:40:25
    skeletal muscles
  • 00:40:27
    but they're muscles that are basically a
  • 00:40:29
    part of the head and neck that are
  • 00:40:30
    derived from these embryological origin
  • 00:40:33
    and so we don't call them general
  • 00:40:34
    somatic efferents we got to be
  • 00:40:36
    complicated and call them special
  • 00:40:38
    visceral efferent neurons all right
  • 00:40:41
    beautiful
  • 00:40:42
    let's move on to the last part all right
  • 00:40:44
    so the last functional classification of
  • 00:40:46
    neurons is interneurons
  • 00:40:47
    it's literally what it sounds like it's
  • 00:40:50
    the neurons between
  • 00:40:52
    the sensory neurons and the motor
  • 00:40:54
    neurons that's it
  • 00:40:55
    so i want you to think think about this
  • 00:40:56
    we have that motor cortex right
  • 00:40:59
    up in the uh the cerebral cortex in your
  • 00:41:01
    frontal lobe
  • 00:41:02
    this motor cortex is going to send its
  • 00:41:04
    motor fibers down and it technically
  • 00:41:06
    goes to
  • 00:41:07
    neurons in your spinal cord right lower
  • 00:41:09
    motor neurons and that goes out to your
  • 00:41:11
    skeletal muscles
  • 00:41:12
    right but this is the motor pathway this
  • 00:41:14
    entire red line is your motor pathway
  • 00:41:18
    coming from maybe the skin or maybe even
  • 00:41:20
    from the actual muscle itself because
  • 00:41:22
    you have receptors there as well
  • 00:41:24
    you can have these particular sensory
  • 00:41:28
    receptors that are taking information
  • 00:41:30
    in and when they go in this is your
  • 00:41:33
    sensory fiber here
  • 00:41:34
    it may stop off on a particular neuron
  • 00:41:38
    in between the motor and the sensory now
  • 00:41:41
    what is this one
  • 00:41:42
    this is a particular nucleus we'll talk
  • 00:41:43
    about later in another video
  • 00:41:45
    for right now i just want you to think
  • 00:41:46
    about it as just kind of a relay neuron
  • 00:41:49
    so if this is a relay neuron let's
  • 00:41:51
    actually switch the color here let's
  • 00:41:52
    make this green so we know the
  • 00:41:53
    difference here
  • 00:41:55
    this relay neuron may fire some action
  • 00:41:58
    potentials
  • 00:42:00
    to another relay neuron and then that
  • 00:42:03
    relay neuron may fire some action
  • 00:42:05
    potentials
  • 00:42:06
    to this motor to the actual motor cortex
  • 00:42:08
    right
  • 00:42:09
    so think about this you have your
  • 00:42:11
    sensory fibers which are taking
  • 00:42:12
    sensations into your central nervous
  • 00:42:14
    system
  • 00:42:15
    they may be going up and then dropping
  • 00:42:17
    off on some relay neurons
  • 00:42:19
    which will then go back and stimulate
  • 00:42:20
    your motor neurons you see how that's in
  • 00:42:22
    between here
  • 00:42:23
    that's called your interneurons to give
  • 00:42:25
    you kind of an idea so that you
  • 00:42:27
    can see that i'm not making these things
  • 00:42:29
    up this later we'll talk about is in the
  • 00:42:31
    medulla a part of your dorsal column
  • 00:42:33
    medial meniscus pathway this is called
  • 00:42:36
    your nucleus
  • 00:42:38
    like gracilis and nucleus cunaitus
  • 00:42:42
    right so these are going to be two that
  • 00:42:43
    you'll talk about that's an example of
  • 00:42:45
    an interneuron
  • 00:42:46
    your thalamus you know your thalamus has
  • 00:42:49
    tons of different nuclei
  • 00:42:52
    and it also has the ability to send its
  • 00:42:54
    action potentials to the motor cortex as
  • 00:42:56
    well
  • 00:42:57
    so it's important to realize that we're
  • 00:42:59
    talking about interneurons
  • 00:43:01
    these interneurons make up most of your
  • 00:43:03
    central nervous system
  • 00:43:04
    and commonly we only refer to them into
  • 00:43:06
    the spinal cord but they're all
  • 00:43:08
    throughout that brain and brain stem
  • 00:43:09
    baby
  • 00:43:10
    so to give you the classic example of an
  • 00:43:13
    interneuron
  • 00:43:13
    with the spinal reflex it's pretty
  • 00:43:15
    straightforward think about this
  • 00:43:17
    you have a sensation coming from the
  • 00:43:20
    skin
  • 00:43:21
    someone touches your skin that sensation
  • 00:43:23
    then does what it moves via the sensory
  • 00:43:26
    neuron
  • 00:43:27
    into the spinal cord from that it acts
  • 00:43:30
    on a
  • 00:43:31
    interneuron that
  • 00:43:34
    intern neuron then sends information to
  • 00:43:37
    what
  • 00:43:38
    to your motor neuron and that motor
  • 00:43:40
    neuron will send that information
  • 00:43:42
    out to the skeletal muscle to maybe
  • 00:43:44
    cause you move because maybe you
  • 00:43:46
    pricked your finger off of something it
  • 00:43:48
    hurt and you had to move it away
  • 00:43:49
    so you see how the interneuron is
  • 00:43:51
    involved in between that pathway this is
  • 00:43:53
    the classic situation
  • 00:43:54
    but also remember that it's present up
  • 00:43:56
    here in that brain and brainstem baby
  • 00:43:57
    all right so that's the intern neurons
  • 00:43:59
    and that covers neurons in general
  • 00:44:01
    all right all right nizhner so in this
  • 00:44:02
    video we talk about the structure and
  • 00:44:04
    function of neurons i hope it made sense
  • 00:44:06
    i hope that you guys
  • 00:44:07
    liked it guys we thank you appreciate
  • 00:44:09
    you for being awesome ninja nerds as
  • 00:44:11
    always until next time
  • 00:44:22
    [Music]
  • 00:44:32
    you
الوسوم
  • neurons
  • dendrites
  • axon
  • synaptic transmission
  • neurotransmitters
  • action potential
  • graded potential
  • neuron structure
  • interneuron
  • axon terminal