Cranial Nerve Function, part 2

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Из курса от партнера Duke University

Medical Neuroscience

1042 оценки

Duke University

Medical Neuroscience

1042 оценки

Medical Neuroscience explores the functional organization and neurophysiology of the human central nervous system, while providing a neurobiological framework for understanding human behavior. In this course, you will discover the organization of the neural systems in the brain and spinal cord that mediate sensation, motivate bodily action, and integrate sensorimotor signals with memory, emotion and related faculties of cognition. The overall goal of this course is to provide the foundation for understanding the impairments of sensation, action and cognition that accompany injury, disease or dysfunction in the central nervous system. The course will build upon knowledge acquired through prior studies of cell and molecular biology, general physiology and human anatomy, as we focus primarily on the central nervous system. This online course is designed to include all of the core concepts in neurophysiology and clinical neuroanatomy that would be presented in most first-year neuroscience courses in schools of medicine. However, there are some topics (e.g., biological psychiatry) and several learning experiences (e.g., hands-on brain dissection) that we provide in the corresponding course offered in the Duke University School of Medicine on campus that we are not attempting to reproduce in Medical Neuroscience online. Nevertheless, our aim is to faithfully present in scope and rigor a medical school caliber course experience. This course comprises six units of content organized into 12 weeks, with an additional week for a comprehensive final exam: - Unit 1 Neuroanatomy (weeks 1-2). This unit covers the surface anatomy of the human brain, its internal structure, and the overall organization of sensory and motor systems in the brainstem and spinal cord. - Unit 2 Neural signaling (weeks 3-4). This unit addresses the fundamental mechanisms of neuronal excitability, signal generation and propagation, synaptic transmission, post synaptic mechanisms of signal integration, and neural plasticity. - Unit 3 Sensory systems (weeks 5-7). Here, you will learn the overall organization and function of the sensory systems that contribute to our sense of self relative to the world around us: somatic sensory systems, proprioception, vision, audition, and balance senses. - Unit 4 Motor systems (weeks 8-9). In this unit, we will examine the organization and function of the brain and spinal mechanisms that govern bodily movement. - Unit 5 Brain Development (week 10). Next, we turn our attention to the neurobiological mechanisms for building the nervous system in embryonic development and in early postnatal life; we will also consider how the brain changes across the lifespan. - Unit 6 Cognition (weeks 11-12). The course concludes with a survey of the association systems of the cerebral hemispheres, with an emphasis on cortical networks that integrate perception, memory and emotion in organizing behavior and planning for the future; we will also consider brain systems for maintaining homeostasis and regulating brain state.

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Neuroanatomy: Surface Anatomy of the Human CNS

We now begin in earnest our lessons on neuroanatomy with the surface of the human brain, including a brief run through the cranial nerves and the blood supply to the CNS. In this module, you will learn the basic subdivisions of the vertebrate nervous system; however, your focus should be on the cerebral cortex. Along the way, you will be challenged to "build a digital brain" that should help you generate and improve your mental “model” of the cerebral hemispheres of the human brain. Another great way to refine your mental model is through sketching and crafting, so please do the learning objectives that are designed to help you make visible (and tangible) your understanding of the cerebral hemispheres.

Overview of the Cranial Nerves19:39

Overview of the Spinal Nerves8:40

Localizing the Cranial Nerves13:35

Cranial Nerve Function, part 116:43

Cranial Nerve Function, part 211:13

Познакомьтесь с преподавателями

Leonard E. White, Ph.D.
Associate Professor
Department of Neurology, Department of Neurobiology, Duke University School of Medicine; Department of Psychology & Neuroscience, Trinity College of Arts & Sciences; Director of Education, Duke Institute for Brain Sciences; Duke University

Alright, so there are a couple of dimension in which I would hope that you

would use this table in your studies. We've been emphasizing the horizontal

dimension, that is looking, one nerve at a time.

Thinking about what are the various components that we would find in that

nerve, so that's one way to approach using this table.

Another would be the vertical dimension and that is to think about okay, what are

the Somatic motor components in the brain stem.

And just think about the nerves, think about their anatomy.

How they attach to the brain stem, and I would suggest that you do so thinking from

superior to inferior. All right, so, march through each column

that way, the Somatic motor, the Branchial motor, the Visceral motor.

And then on the sensory side, think about taste, how is taste conveyed to the brain

stem. And so on.

And I think you'll find that this table is not quite as daunting as it might first

appear. Well that's good because when we get to

the actual anatomy of the nuclei in the brain stem that connect to these nerves.

It will seem a bit overwhelming so I might ask you to brace yourself for that but we

can get through that together. And hopefully this chart in front of you

will be one way to organize your understanding of these nuclei by name and

by location as well as by function. Okay, well, I'm going to try to simplify

this for you just a little bit. Borrowing a scheme that I've learned from

my colleague here at Duke Doctor[UNKNOWN]. Doctor[unknown] suggest that we can think

of the cranial nerve as being related to 16 cranial nerve nuclei.

And these 16 nuclei can be grouped into 4 groups of 4.

So it's sort of 4x4 equals 16 perspective on the cranial nerve nuclei.

So 16 cranial nerve nuclei that are sub divided into 4 groups of 4.

3 of these groups are motor nuclei. So that accounts for 12 of the 16 nuclei.

There are 4 Somatic motor nuclei, 4 Branchial motor nuclei and 4

Parasympatheic motor nuclei to talk about. Well, that accounts for 12 of the 16 so

that must mean that there is one group that's sensory nuclei and actually that

group can be subdivided further according to the chart we saw on the previous slide.

But to make this 4x4 frameworks stick, I think it might be helpful just to avoid

thinking about that subdivision at the moment.

And consider 4 groups of 4 nuclei. 3 motor and then 1 group of sensory

nuclei. Okay, now let's see how that 4x4 scheme

maps now onto this chart where we've just gone through the cranial nerves that

attach to the brain stem and identify the function associated with each.

So what we're going to do is talk about the nerves, but we're going to deal with

them one column at a time. Okay?

So let's go ahead and, and do so. The 3rd nerve conveys Somatic motor output

to muscles in the orbit that moves the eyes, as I suggested.

And that outport is coming from a nucleus called the ocular motor nucleus.

The next Somatic motor nucleus that we encounter is just a little bit inferior in

the caudal part of the mid-brain, and that's associated with the 4th nerve,

called the trochlear nerve. So, 2 Somatic motor nuclei in the

mid-brain. Oculomotor superior and trochlear just

inferior. Now, the next Somatic motor nucleus we

have in the caudal pons and it's associated with the 6th nerve.

It's the abducens nucleus. And then, the final Somatic motor nucleus,

the 4th of that first group is down in the medulla.

In the upper part of the medulla associated with the roots of the 12th nerve and it

is called the Hypoglossal nucleus. So there is our first group.

There is our first 4 nuclei associated with somatic motor control.

Now for Branchial motor, we have the tri-germinal motor nucleus.

It's the motornucleus that grows out, the motoraxons and the trigeminal nerve and

this supplies to motor output to the muscles of chewing or mastication.

The 7th nerve the nucleus there is called the facial nucleus.

And that nucleus is responsible for governing the muscles of facial

expression. Okay, so far so good.

We've identified six cranial nerve nuclei. And the names of these nuclei all match

the nerve that they contribute. That they contribute to.

Well, that won't always be the case as we're about to see.

The Branchial motor component in nerves 9 and 10 comes from a nucleus appropriately

named called the nucleus ambiguus. It's very difficult to see in our standard

histological preparation of the brain stem which resembles a myelin stain.

Of course if we stained for the presence of cell bodies, especially for motor

neurons, we'd see the nucleus ambiguus quite clearly.

But usually, histologists look at myelin stain sections of the brain stem, and it's

quite obscure. So that's the nucleus ambiguus supplying

Branchial motor outflow through nerves 9 and 10.

The Branchial motor outflow through nerve 11 comes from the accessory nucleus in the

upper cervical segments of the spinal cord.

Alright, what about the four parasympathetic nuclei?

Well, beginning with nerve 3, there is a contribution that is responsible for the

constriction of the iris. That comes from a nucleus called the

Edinger Westphal which sits just superior and a little bit lateral to the ocular.

The motor nuclei up in the mid-brain at the level of the 3rd cranial nerve.

The next place where we have parasympathetic outflow is associated with

nerves 7 and 9. And that outflow comes from a set of

nuclei that we call the salivatory nuclei. Now we could subdivide them into a

superior excuse me a superior and an inferior group.

But to keep this 4x4 scheme going, we'll just collectively consider them the cell

of a toy nuclei. Okay, well, the next major parasympathetic

outflow to consider comes from 2 nuclei. A division of the nucleus ambiguous, which

is separate from the one that provides Branchial motor outflow.

This division is responsible for the cardio inhibitory output that goes to the

heart from the vagus nerve. Well, the other major parasympathetic

outflow to consider in the vagus nerve comes from a nucleus called the dorsal

motor nucleus of the vagus nerve. Alright, well that accounts for our, three

groups of motor nuclei. So lets just make sure we've got more

here, so that's 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12.

Okay. So, we got three groups of four motor

nuclei. Alright.

Now on the sensory side. Okay.

We have 3 nerves in the brain stem that convey a sense of taste back in to the

central nervous system. The all supply the same nucleus, actually,

they supply the rostral division of the nucleus.

The caudal division of the nucleus is the recipient of the general visceral

sensations that are involved in regulating our cardiac rhythms, our blood pressure,

and our respiratory rhythms. And that nucleus is called the nucleus of

the solitary tract. Solitary tract is a very visually striking

tract. And the dorsal part of the tegmentum of

the medulla and there's a gray matter of nucleus surrounding it.

We call that the nucleus of the solitary tract.

So, notice there are two divisions of it and as I mentioned the rostral division is

concerned with taste. The caudal division is concerned with

visceral sensation. Our general somatic sensory system is

again conveyed via multiple nerves, but to, to one nuclear complex.

And that nuclear complex is the trigeminal nuclear complex.

Now when we get into our discussions of somatic sensation including

mechano-sensation and pain and temperature sensitivity.

We'll see that we can subdivide this trigeminal nuclear complex into 3 major

parts, but we won't get into that now. We'll just recognize this as one nuclear

complex. And then lastly, our Special sensory

nuclei in the brain stem include our cochlear nucleus and our vestibular

nuclear complex. Okay, let's see how we've done here with

our numbering scheme now. So we counted 12 motor nuclei here's 1

sensory nucleus, here's the 2nd sensory nucleus and then a 3rd and a 4th.

Okay, so we've accounted for our 4 sensory nuclei to add to our 12 motor nuclei,

giving us a total of 16. Alright, well I hope that scheme has

helped you. We have lots of different ways to assist

you in learning these nuclei and how to organize them.

One additional method is shown in a slide that comes from the textbook that you may

choose to read along with these tutorials. And this scheme is just a little bit

different from the one that I've showed you but it, it still basically lays out

subcategories for motor control and for sensation and shows you how the motor

nuclei can be arranged accordingly. Well I hope this has been helpful.

It's been sort of a whirlwind tour through the cranial nerves emphasizing their

functions. And then just giving you some handle on

how those functions can be related to the nuclei of the brain stem.

In a different tutorial, we'll actually see those nuclei.

And find them in histological sections. So, that will be forthcoming.

But before we get there see if you can't rehearse a little bit, in your own mind,

this 4x4 scheme for mapping the functions of the cranial nerves to the nuclei of the

brain stem. I'll see you next time.

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