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 2
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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
Okay, well, let's now look in a little bit more particular detail at different
nuclei of the hypothalamus, and I want to give you a sense of what is the diversity
of function that is attributable to different nuclei in this collection.
that we call the hypothalamus. Now, I don't intend for you to know all
of this detail, I really don't. I give some of this to you in the
tutorial notes, mainly as a way for you to just spend a few minutes thinking
together with me, about the hypothalamus and the diversity of systems that it
impacts. there is one however that I want to
highlight for you, because we're going to come back to this in a later session.
Okay, I mentioned one can look at the hypothalamus in different axes, from
front to back, from anterior to posterior, from medial to lateral.
What I want to do is just highlight a few nuclei that catch my attention at least,
going from the medial to lateral axis of the hypothalamus.
And let's begin right along the walls of the third ventricle.
There's a very interesting pair of nuclei that we find right along the wall of the
third ventricle and just inferior to it. these nuclei are found in what we might
call the Periventricular zone, right around the ventricle.
There is a nucleus called the periventricular nucleus and there is another
one called the arcuate nucleus and these nuclei are intimately related to the
production of hormones in the anterior part of the pituitary gland.
This is the part that we call the adenohypophysis.
So the anterior pituitary receives hormones that are produced by cells that
sit in this periventricular region of the medial hypothalamus.
And those hormones enter the portal circulation where they are then
Transported via this blood supply to the anterior part of the pituitary.
These hormones, we call them releasing factors, then have an impact on the neuro
secretory cells of the anterior pituitary, and these cells then produce a
hormone that enters the general circulation.
And can impact physiology throughout the entire body, so right along the medial
border of the hypothalamus is where we find those neurons that govern the output
of the anterior part of the pituitary. Well, moving on just a bit more lateral
in the color code here these would be these darker so, solid shaded regions in
here. we have a variety of interesting nuclei
that do all kinds of different functions. Let me just highlight a few of them.
There is a set of nuclei called the paraventricular nucleus and the
supraoptic nucleus. So here's the supraoptic nucleus, it's
called supraoptic because it sits just above the optic chiasm.
And in a slightly more dorsal position is this paraventricular nucleus.
these nuclei are, are two of many that we find in this more medial zone of the
hypothalamus. I mentioned the paraventricular
supraoptic nuclei because these are the nuclei that have the neurons that grow
their axons through the infundibulum, that is, the stalk of the pituitary, and
release hormones directly into the general circulation in the
neurohypophysis or the posterior part of the pituitary gland.
Okay? So the periventricular zone is where we
find our neurons that are engaging the anterior part of the pituitary.
And then in this more medial zone, that's where we find the super optic and
paraventricular nucleus that are releasing hormones into the posterior
pituitary. Well there are other neurons in this
para-ventricular nucleus in particular, that are not releasing hormones in the
pituitary rather they are growing axons and descend into the brain stem, and even
into the spinal cord. And these para-ventricular neurons that
grow these long axons are involved in coordinating the output of pre-ganglionic
neurons in the parasympathetic and in the sympathetic divisions of our visceral
motor outflow. So the paraventricular nucleus is a very
important structure in regulating various dimensions of our behavioral response.
Okay, I'd like to highlight a few more nuclei here in this medial zone.
generally speaking, this medial and lateral preoptic area here.
And I'll, I'll guess I'll highlight the medial preoptic region.
this is a, a really fascinating part of the interior hypothalamus.
This is a part of the hypothalamus that is involved in various aspects of
coordinating reproduction. And sexual behavior.
So this is a part of the hypothalamus that we think is especially involved in
defining our sexuality, and motivating sexual activities, and here there are
circuits that are coordinating various aspects of mating behavior, and in women
various dimensions of pregnancy, and postpartum behavior.
So, this preoptic area has connections with important parts of our limbic
forebrain, that are involved with emotion, as you might expect our emotions
are important sources of input to circuits that are mediating sexual
behavior and sexual activities. This medial pre-optic area is also
involved in governing the release of urine in the process of micturition.
We'll have more to say about that in the final part of this tutorial.
But just keep that in mind. The medial preoptic area is also involved
in governing bladder function. Other structures in this medial zone
worth mentioning include the suprachiasmatic nucleus.
So this is a small nucleus that sits just above the chiasm here, just a little bit.
Medial and anterior to where I highlighted the super optic nucleus.
So this is the suprachiasmatic nucleus. Hopefully, that's easy to remember.
And I do want you to remember this nucleus, because this is a nucleus we'll
come back to when we talk about the regulation of sleep.
The suprachiasmatic nucleus is the master clock of the human body.
This is the place where we have neurons that generate a circadian rhythm, that
is, a rhythm that runs roughly 24 hours, not precisely 24 hours, we'll mention
that in a later tutorial, but it allows us to establish a daily rhythm For
behavior, for the release of hormones that can affect our body's physiology and
our behavior. so very important part of the
hypothalamus, and it's that part that I mentioned when we discussed the visual
pathways that receives input from the special set of photosensitive ganglia
cells in the retina. So by this connection with the retina,
this suprachiasmatic nucleus can be entrained to our natural cycles of light
and, and darkness, of daytime and nighttime.
There's another set of medial zone nuclei that I would mention.
the dorsal medial nucleus. and also the ventral medial nucleus.
These two nuclei seem to be involved in some other dimensions of reproductive
behavior. And even parenting behavior.
At least based on animal studies one might expect that.
these nuclei seem to contain circuits that are involved in the feeding system.
helping to motivate the consumption of food.
As well as mediating signals that are related to satiety.
so very important networks here for motivating the ingestions of foods and
possible also particular appetites for things like salts.
Or particular food substances that we might happen to be in deficit of.
There are other circuits here that are also involved with water balance and
thermo-regulation. Well lastly I would highlight this more
lateral part of the hypothalamus indicated by this stippled region here.
So there are nuclei out here more laterally that are involved in really a
variety of functions that pertain to attention and arousal.
Now these aren't the only neurons in the brain that are important for those kinds
of functions. But these parts of the hypothalamus seem
to have broad connections, especially with the cerebral cortex.
And they seem to be in a position to modulate the way the cortex responds to
other kinds of inputs. So in that sense, the lateral
hypothalamus seems to have role to play in modulating levels of vigilance in the
brain. in a manner might be similar to signals
that are motivated by the amygdala, as well as some of the biogenic amine
systems in the brain stem. Well, as I said when we got into this
slide there are way too many details that are beyond the scope of this course to
expect you to take in, in this brief tutorial.
rather what I want you to do is at least remember this important suprachiasmatic
nucleus, cause we're going to come back to that.
But even more so, I hope you get just an impression that there are a variety of
physiological functions that can be absolutely central to motivated human
behavior that are coordinated at the level of the hypothalamus.
Well, now that you've had a bit of a sense of some of the functions associated
with nuclei of the hypothalamus. I want to conclude this session by
talking about a particular clinical condition called Horner syndrome.
Now Horner syndrome is relatively common, we might see it in a variety of patients
for different reasons, and it is a presentation of signs and symptoms that
are typically associated with the face. Now Horner's syndrome could be bilateral
but it more commonly is unilateral and its characterized by a set of signs that
can be best appreciated clinically by focusing on the region of the eyes.
So what we find most significantly is miosis, which is a constriction of the
pupil. Now what you're looking for when you
examine the diameters of the pupils is not so much an absolute size but an
asymmetry. In the case of Horner's Syndrome what we
see is the effected iris has a smaller pupil than the normal iris.
Well it might be somewhat difficult to appreciate what is normal, but I think
you can see that the dimension of the pupil is smaller in this patient's right
eye compared to the left eye. So this is miosis.
It's evidence of an abnormal constriction of the pupillary muscle.
Well, in addition to the constriction of the pupil, we also see a drooping of the
eyelid associated with Horner's syndrome. So this might be a subtle sign But, it's
one that you should look for nevertheless.
And, one might also get the impression that the eyeball itself, the globe, is
somewhat sunken into the orbit. There are some other signs and symptoms
associated with Horner's syndrome that may be a little more difficult to
appreciate clinically. But perhaps to suit patient interview you
can Confirm their presence or absence.
one sign you may be able to detect if you were to put your fingertips on the, on
the cheeks of your patient. You may discover that the side with the
constricted pupil actually feels a little bit warmer to the touch than the opposite
side. Now, if you were to ask the patient about
their sweat response to hot environments or to exercise you may discover that the
side with the smaller pupil doesn't actually seem to sweat as much as the
opposite side of the face. Well, can you think of what all of these
signs might have in common? Do you remember what's responsible for
the dilation of the pupil? What about the ability to keep our
eyelids open throughout the day? And what system supplies innervation to
the sweat glands? Or what do you think an increase in the
temperature of the skin might tell you. About the tone of the vasculature that's
supplying these cutaneous structures of the face.
Well, hopefully, I'm leading you along the path that allows you to understand
that what all of these systems have in common, is sympathetic control.
Well, Horner's Syndrome can result from an interruption in the pathway that links
the hypothalamus up here in the ventral and anterior part of the diencephalon
with our ganglionic neurons. Which, with respect to the governance of
these structures in the face Are localized to the superior part of that
sympathetic trunk. Specifically, the pupillary dilator
muscle is supplied by ganglionic neurons that sit in the superior cervical
ganglion and grow an axon through the carotid plexus to reach the orbit where
there's innervation of this dilator muscle of the iris.
So, just given the broad distribution of this system from hypothalamus to face or
to iris, you could imagine that, one could have a legion or some other kind of
disease process that would affect this pathway, either within the nervous system
or outside of the nervous system, and produce Horner's Syndrome.
And indeed, one might have, damage to the neck, that's outside of the nervous
system that potentially could impact, the, superior aspect of the sympathetic
trunk and produce a Horner's syndrome. Or one might have damage within the
nervous system itself. So for example, if there were a stroke in
the lateral tegmentum of the brain stem. Here is a representation of the medulla.
we potentially could have a Horner syndrome in conjunction with signs and
symptoms that would help you localize the lesion to this particular level.
In addition, one might have an injury to the cervical spinal cord, or perhaps even
to the thoracic spinal cord, that might impact the ability of the hypothalamus
and the brain stem to interact with the intermediolateral cell column, or one
might have damage to that cell column itself and produce Horner's syndrome.
So, of course, one can have an injury to the neck and have some kind of a, of a
isolated Horner's syndrome, at least isolated with respect to other
neurological signs and symptoms. But whenever we have the image within the
CNS itself, we're likely to have a Horner's syndrome together with other
neurological signs and symptoms. That, you'll piece together as a means of
localizing the injury. Well, I would suggest that we conclude
this, segment of our tutorial, focusing on the hypothalamus, with a couple of
study questions. So I'll invite you to think through those
study questions, and then we'll, finish up on the visceral motor system and
indeed all of unit 4. By using one physiological system as a
way of demonstrating how visceral motor control is integrated with sensory
signals, and coordinated with somatic motor control, to govern behavior.
And the example I'm going to choose is called micturition, or otherwise the
voiding of our bladder, urination. Well, I know I've had just a little bit
just too much coffee this morning. So, before I talk to about voiding the
bladder. Well, I think I need to do it myself.
Let's take a short bathroom break and when we come back Let's talk about how
the nervous system governs maturation.
