Where is the thalamus
Where is the thalamus?
[Music]
I've been talking about the Alamos this
week does that ring any bells with you
so
nuru Anatomy right let me show them this
kept it more lighting so the thalamus
where is the thalamus and what does the
thalamus do it's difficult well maybe
it's not difficult getting thoose est
bellyful of us but it's difficult to
talk about the thalamus for too long
because too much detail but since I
talked about it this week and it's
something we've been building up to with
our neuroanatomy in the medicine program
here I thought I'd recap it here I think
the important things about the thalamus
are you should be able to find it and
you're going to be looking at brains
I imagine on M R and CT scans of the
head right so we should have a look and
see how you can find the thalamus in
relation to other structures within the
cranial cavity in the brain right so
where is the thalamus how do you find it
if we look at it from different
perspectives improve it what's nearby
and then what does the thalamus do maybe
we should turn it around maybe we should
just do what the thalamus does now and
then go and find it as that same yeah
right the thalamus then so the thalamus
is often considered briefly a sensory
sieve all right so it's it forms in the
embryo in the dying careful on so if the
TN kept healing careful on forms the
cerebrum the diencephalon forms of stuff
in the middle what this means is that
it's between the higher centers of the
brain and the spinal cord which means
it's likely that an awful lot of stuff
goes through the thalamus between the
brain and the spinal cord
right now the stretches and indeed
that's what we see so consider
you are an organism covered in a huge
amount of sensory apparatus just think
about how many sensory nerves you have
on a patch of skin on your body then
think about how much skin you have on
your body right now you're not thinking
about your little finger all the time
but you probably are thinking and you
can probably feel the little finger on
your right hand now that I've mentioned
it right so all that sensory information
is available to you but you're not aware
of it all the time as soon as a fly
lands on your on you're instantly aware
of that fly on your arm and you're
probably brushing it off right
that's the thalamus doing that so the
thalamus is receiving all of this
sensory information from the body and
it's discarding most of it most of it is
so it's not important it's not
interesting but as soon as a fly lands
in your arm it says that that's
interesting and it raises that sensory
information to a higher level so it goes
to your somatosensory cortex to your
cerebrum your consciousness is now aware
of the fly on the skin there but you
know the breeze the changing temperature
all those other things that the sensory
apparatus in our skin is detecting
you're not really aware of your brain is
not the the thalamus chooses not to send
that on right and it's more than that
the thalamus is also receiving sensory
information from vision so it has you've
may have heard of the lateral geniculate
nucleus in the in the visual pathway
right so you've got your optic nerve
goes through the optic chiasm becomes
the optic tracts goes to the lateral
geniculate nucleus goes through the
thalamus that's hanging off the thalamus
and into the visual cortex at the back
that's it's also passing this sensory
information on and it's also linked to
the is in the inferior colliculi of the
midbrain so auditory information that's
coming in is also passing through the
medial geniculate nucleus of the
thalamus then going on to auditory
sensors so it's it's it's receiving all
sorts of sensory information and
filtering and passing and doing magical
things with it it also receives taste
it's receiving all the spinothalamic
tracks were these dorsal columns of our
spinal cords they're all going to the
thalamus and then there's another sign
apps and
the connection with the third neuron
after the cerebrum the one sense that it
doesn't receive as far as I'm aware is
smell the olfactory nerves cranial
nerves wanna direct extensions of the
cerebral cortex it seems so that sensory
information goes straight back into the
brain doesn't go anywhere near the
thalamus but otherwise the thalamus is
it receives all the sensory information
and decides whether it's useful or
relevant or not maybe the cranial nerves
so trigeminal nerve cranial no 5 the
major sensory nerve of the face that
sends its information back into the
thalamus so you can imagine then that a
lesion and injury to the thalamus on one
side is likely to cause a loss of
sensation from the other side of the
body depending upon which part of the
phallus much maybe being injured but
it's a little bit more complicated than
that because as we look at the thalamus
and we look at the wiring we look at the
connections to it we see it's also
connected to the cerebellum it's also
connected to the basal ganglia and those
are involved in movement right in the
initiation of movement in the storage of
sequences of movements your handwriting
is stored in your cerebellum here your
signature is there your dance moves are
all stored in the cerebellum all that
sort of stuff and the basal ganglia is
so important in the initiation
initiation of movement and and the
coordination of movements these things
are linked up to the cerebellum as well
which maybe isn't too surprising if you
think about how we need all that
proprioceptive information all that
sensory information to work with the
motor information so that we can make
these seemingly simple movements which
are in fact incredibly complicated as
I'm moving my arms around I'm shifting
my balance as some muscles are
contracting other muscles got to relax
all that sort of stuff but then when we
look further at the thalamus we see that
is also connected to the limbic system
the limbic system is involved in memory
emotion things like that the hippocampus
is part of the limbic system and
famously that gets a large or in black
cab drivers so taxi drivers in London if
you look at their hippocampus once
they've done the knowledge was they've
learned all the streets of London their
hippocampus is get bigger it's a memory
and spatial awareness and emotional that
sort of thing is also linked to the
thalamus
maybe the triggering of memories through
vision or the the storage of visual
information
so obviously memories are what we
perceive so we make sense that the
sensory information that goes in to us
may well pass through the thalamus and
be linked to the limbic system in terms
of memory storage of course pain is a
sense that goes through the thalamus and
pain has an emotional context to it so
maybe there's that linking there between
the limbic system and emotion and pain
coming in through the thalamus anyway
there's a lot going on with the thalamus
also it seems that there are loops
between the thalamus and the cortex and
the cortex doesn't act in isolation it
includes the thalamus in some of these
other processing functions so the
thalamus is very central there's a lot
going on there it's very important so in
fact if somebody has a lesion to their
plan emotional injury it may well not be
as simple as a change in in sensory
information a change in sensation they
may will also experience other other
problems motor function problems and
general behavior changes so the phallus
hopefully the point I've got across is
really important and really useful so
where is it that's what you want to know
right there all right you didn't see
that okay it's it's here so here's a
midsagittal section of the head here is
the do you just like to see this you can
see the cerebral cortex here this is the
middle cerebral artery coming around
here here's the nasal cavity frontal
sinus sphenoid sinus there's the
pituitary gland up here here comes the
spinal cord into the medulla oblongata
the pons the midbrain across here
here's the corpus callosum up here so
this is the thumbless
that's where you find it I don't know if
you can see but it's a little space it's
an ovoid shape and there's a thalamus on
either side so where they meet they have
this into thalamic adhesion it's
doubtful whether there are any neurons
crossing from side to side that ever
there might be okay this is the
hypothalamus down here and there's a
space here then between the left and
right sides and that space is the third
ventricle of the ventricular system so
the third ventricle and we have the
cerebral aqueduct down here
and there's the fourth ventricle in
there and this is the cerebellum so
that's where the thalamus is it's very
central and there are two one on either
side the information from the spinal
cord comes up and from other parts of
the body goes into the thalamus then
there are a number of connections with a
number of other structures so the
thalamus is just lateral to the midline
if we get another view so then here are
the lateral ventricles here and here if
we slice again we see the lateral
ventricles but they're being cut and now
here we see the thalamus on either side
so you can see how it's an ovoid shape
slice again and here we go so now you
can see most of the thalamus you can see
that ovoid structure in the midline here
we have the third ventricle that little
slit space and here we have the basal
ganglia of the Globus pallidus and the
putin the lenticular or the lenta form
nucleus that this is the thalamus here
which was very much in the middle
and as we slice again then we're through
to the midbrain that's good okay so now
you know where the thalamus is and you
know what it does pretty much okay so
the thalamus is important and you know
how to find it
let's have a look on some radiographs
now let's have a look on some of em our
images and see where the thalamus is
from different perspectives okay so the
feminists from a transverse section the
thalamus in a sagittal section mid
sagittal section
well ich and the thalamus from a coronal
section so can you see the the space is
there of the lateral ventricles they're
always good landmarks aren't they
looking at em our images okay a little
bit of neuroanatomy hopefully that
wasn't too painful I'm just a little
focused on a particular structure within
the brain hopefully you know a little
bit more about it I don't know if we'll
be doing any more neuroanatomy next time
how do you feel about neural Anatomy
it's very difficult to do with models
for one thing a lot of is very easy so
tarik but there you go
anyway okay see you next time
