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.