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.
Hypothalamus, part 1
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来自 Duke University 的课程
Medical Neuroscience
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从本节课中
Movement and Motor Control: Visceral Motor Control
We conclude our survey of movement and motor control by considering the visceral motor system, perhaps better known as the autonomic nervous system. As you study this lesson, consider how the disparate physiology of the viscera has impact not only on the internal state of the body, but also on implicit processing in the forebrain. We will return to this matter when we consider the neurobiology of emotions near the conclusion of Medical Neuroscience
与讲师见面
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
Welcome back to the next part of our tutorial, on the Visceral Motor System.
In this session I want to focus on the hypothalamus.
So again, our discussion relates to the complexity of the brain and some of the
circuitory of the brain that is genetically determined.
And it provides the foundation for the operations of the, of the elements of the
nervous system that are the focus of this session.
And for us it's going to be the circuitry of the hypothalamus.
So my learning objective for you in this session is that I want you to be able to
describe the organization of the hypothalamus.
And identify several functions associated with key hypothalamic nuclei.
Well, we concluded the first part of our visceral motor tutorial by focusing in on
this central autonomic network and we talked about the
Ascending aspects of sensory signals that are derived from the viscera, and how
they are integrated within this central automomic network.
And the outflow back down to our visceral motor end organs is coordinated in a
large measure by this key structure in the ventral part of the diencephalon
called the hypothalamus. So I think it will be well worth your
time to just think we me for a few minutes about the hypothalamus structure.
And then the myriad functions associated with the circuits that are localized to
different structures that are part of the hypothalamus.
Okay, so with that as our context, let's look at the anatomy of the hypothalamus.
So I'll just remind you with this midsagittal view of the human brain that
the hypothalamus is found in the ventral aspect of the diencephalon.
And in a somewhat anterior position. Now I've drawn a triangle here because
this is roughly the region where we find the hypothalamus.
So this triangle is essentially the third ventricle, and the hypothalamus forms the
walls of the third ventricle. And obvisously extends from the
ventricular surface into the depth of the brain.
and this ventral part of the diencephalon.
So this triangle is really formed by three structures that I think you can see
quite plainly here in this image. So one structure is found right here.
And this is a white matter structure that crosses the midline.
Now, it's not the corpus callosum, the corpus callosum is up here.
It is another commissure. So perhaps you can think of what that
structure is. I'll give you just a moment and everyone
shout out together. It's the anterior commisure, right here.
So that anterior commisure is abit of a visual landmark that defines one point of
this triangle that can help bound your recognition of the hypothalamus.
Okay so the low point of the triangle is right here.
And again, does anyone know what this is? this is a structure associated with the
visual pathway, connecting the retina to the diencephalon, and the pretectal
region of the upper part of the brain stem.
This is actually the optic chiasm, okay? So hopefully you can recognize that.
So those are two points of the triangle. The third point is actually a part of the
hypothalamus itself. And that is this medial ball like
structure that sits very close to the mid-line.
There's a pair of them, one on either side.
And again who knows what this is? This is one of the two mamillary bodies.
Okay, so these are the three visual landmarks that form this triangular
region that allows us to recognize the location of the hypothalamus.
Well this is the gross view of the hypothalamus.
A more detailed anatomous view of the hypothalamus would really be quite
different. So, if we were to look now at this
triangular region in some detail, I, here again is our triangle, connecting our
anterior commissure, our optic chiasm, and our mammillary body.
What we find is that the hypothalamus is not just one, uniform structure, but it
really is a region that consists of many different nuclear divisions.
In this respect, the hypothalamus is quite like the thalamus.
Where in the thalamus as hopefully you are now quite comfortable with this idea,
there are a number of discrete Nuclei, discreet clusters of cells, that have
distinct input and output connections. And the information that's conveyed via
those inputs and outputs, helps to define, the functional distinctions of
each of those divisions. Well the very same concept applies to the
hypothalamus. So what we find in this figure, is a
rendering of just a subset of the nuclear divisions of the hypothalamus that might
be recognized. So the color code just organizes these
nuclei in a rostral to caudal, or an anterior to posterior, progression.
But there's also a medial to lateral progression of nuclei that I want to
highlight for you in just a moment. Well, the big picture here is that the
hypothalamus is comprised of a number of discrete nuclei that maintain distinct
patterns of input and output connections. And many of these nuclei are associated
with very particular functions. And I'd like to highlight a few of them
for you in just a little bit. But, before we get there, what I'd like
to be able to do is to give you a bit of a broader picture of what the
hypothalamus and it's many nuclei are involved in.
I'd like to give you a sense of the general mechanism of hypothalamic
function in each of these circuits. And then we'll talk through some
particular examples, that will give you a sense of.
What kinds of functions might be associated with hypothalamic nuclei?
Okay, well thinking very broadly, I would assert that the hypothalamus regulates
five basic functions. It regulates blood pressure and
electrolyte balance. And it does so by modifying a variety of
behaviors and physiological functions that can impact blood pressure and
electrolyte balance, such as, seeking out fluids.
Drinking generating an appetite for salts.
Adjusting the osmolarity of our blood. And adjusting our vasomotor tone, which,
as you know, has an impact on our blood pressure.
The hypothalamus can regulate body temperature, and it can do so, again,
through various physiological and behavioral means.
the hypothalamus has governance over thermogenesis in the physiological
systems of our body. The hypothalamus can also motivate
behaviors that result in seeking, warmer clothing or warmer environments, or the
removal of clothing and the seeking of cooler environments.
The hypothalamus can regulate energy metabolism by coordinating our feeding
behavior. This is a huge topic.
I wish we had more time in medical neuroscience to really impact the role of
the hypothalamus in the feeding system. but perhaps in future editions of the
course we'll try to create some additional time for that.
Well, the hypothalamus helps to regulate the intake of food and its digestion.
And it also helps to establish a sense of satiety when our intake of food should
cease. And as you might imagine, there are a
variety of systems, that can become disregulated, and can result perhaps in a
variety of eating disorders. including obesity which is a huge problem
in many parts of the world and including here the United States.
So we definitely need to direct additional attention in understanding the
governance of our feeding system and the various disfunction or dis regulations of
this part of the brain. Well the hypothalamus is also involved in
adjusting metabolic rate. Which also obviously has a major impact
on energy metabolism in the body. The hypothalamus has really a fascinating
role to play in governing reproduction. And this involves a variety of different
aspects of reproductive activity. It involves the physical behaviors that
are associated with sex and mating activities.
It involves a sense of sexual identity and sexual orientation can be influenced
by hypothalamic circuits. There are hypothalamic circuits that
operate in females to coordinate the various physiological changes that are
necessary to support pregnancy. And then in the postpartum period,
lactation and the neurishment of the infant.
And then lastly. the hypothalamus is very important for
coordinating the responses that support what we call allostasis.
That is changing the internal environment to the body in order to respond to
emergency conditions. So, the hypothalamus is involved in
coordinating the distribution of blood flow.
To where it's needed most given the contingency that we're faced with.
It is involved with coordinating the release of hormones, governing the neuro
endricine relation. And, in this case of emergency response,
is increasing the release of stress hormones that help to mobilize the body
for action. And the hypothalamus even has
interactions with our immune system that likewise are important for mediating how
we respond to emergency conditions. Well this list could be longer than five
items as I'm sure you can imagine. And perhaps we could kick the, to a
discussion forum. a richer discussion of the various
dimensions of hypothalamic coordination of homeostasis and allostasis but I think
I'll leave it here for now. And now let's talk about the general
mechanisms by which the hypothalamus can control these five basic functions.
Well I see the hypothalamus as sitting in a key position in the nervous system
anatomically and physiologically. It's getting sensory inputs from visceral
and somatic sensory pathways. It is sensitive to chemosensory signals.
in some parts of the hypothalamus directly sensitive to the chemistry of
the blood and the extracellular fluids. in other parts receiving ascending
sensory information from the nucleus of the solitary tract and it's relays into
the hypothalamus regarding the chemical environment of the body.
The hypothalamus is also sensitive to the signaling derived from humoral factors
that are circulating in the blood. While all of this sensory information is
integrated with contextual information that's derived from the telencephalon.
Largely the orbital and medial parts of the prefrontal cortex.
Other parts of the cerebral cortex project to the hypothalamus as well, as
does the amygdala and the hippocampal formation in the medial parts of the
temporal lobe. So the hypothalamus is integrating
context, it's integrating sensory signals.
And it's giving rise to output signals that are coordinating our visceral motor,
our somatic motor, and our neuroendocrine systems.
And the result is the production of appropriate behavioral responses, that
reflect the coordinated activity of all these different dimensions of movement to
produce behavior. One important concept in hypothalamic
control that we're still trying to understand is this notion of biological
set points. So this integration of context and
sensory signal is referenced to some measure of homeostatic set point.
Now we don't really understand this concept that as it's played out in neuro
biological terms for very many of the systems that are coordinated in the
hypothalamus. But we suspect it's a common mechanism
and the implementation of this mechanism undoubtably gets us deep into moleculer
biology of this circuitry. And how molecular mechanisms are
mediating these set points. And how signaling within the neuron and
perhaps even within the nucleus is producing patterns of gene expression in
space. In particular, in circuits and in time in
different conditions that demand different sorts of responses.
Well, we'll learn a little bit more about this when we talk about the regulation of
sleep and wakefulness. there are circuits in the hypothalamus
for which the molecular set points are reasonably well understood.
So I'm going to unpack a little bit of that in a later session.
But for now I'll just broadly emphasize this general mechanism of hypothalamic
function of integrating context and sensory signals and referencing against a
set point. And, with deviation from that set point
we have implementation of some kind of behavioral change.
