Alright Ninja Nerds! What we're going to
do in this video is, we're going to talk
about the pineal gland. Alright, so the
pineal gland is really cool a little gland.
It's located in what's called the diencephalon.
So what's the diencephalon? A little bit
nothing crazy, a little bit into a neuro
anatomy here. The diencephalon is
actually consisting of a couple
different structures, it consists of the
thalamus, the hypothalamus, and what's
called the epithalamus, which consists
of the pineal gland and that's also
called the habenula or
habenular commissure. But it's kind of deep to
what's called, this your cerebrum right
here, all of this is your cerebrum, it's
deep to the cerebral cortex which a
bunch of grey matter inside deep to the
cerebral cortex. Okay, now here I'm
zooming in on the pineal gland. Okay, so
this right here is our pineal gland. So
again this right here is the pineal
gland, just to kind of give us anatomical
position here, this is the thalamus and
this right here is a nuclei present
within the hypothalamus and extremely
important nucleus, extremely important.
It's called the suprachiasmatic nucleus.
This is your midbrain, pons, medulla and then
the part of the spinal cord down here and
cerebellum. This is an important ganglion
we're not going to talk too much about
it, I'm just going to mention it we'll
get to it in a second though and this is
the optic nerve and then this is going
to be the eyeball right with on the back
part of it, the important part which
consists of all the photoreceptors like
the rods and the cones, this is going to
be the retina right there.
Here's the eyeball, this green structure
is going to be the retina and then we
have a lot of these ganglion cells that
are actually bringing this information
to the suprachiasmatic nucleus. Alright.
Pineal gland,
what is it function? It's function is to
be able to regulate our sleep and wake
cycles, our diurnal cycles. Alright and
it also plays other roles that we
by discussing a tiny bit of detail.
Alright, so here we go.
Did you know the also call the pineal gland
the third eye? Why? So you know that the
retina of the eye has a direct
connection to the pineal gland or kind
of indirectly, we can actually say.
Let's say here we actually have in red,
let's show this as specifically light.
So this is denoted to say light.
And then we will have over here in
black we'll describe this as darkness.
Right, so darkness okay.
Whenever there's light, what it does is
it stimulates the action potentials down
this axon right? And then triggers
different types of reactions in the
suprachiasmatic nucleus, which sends
signals down to this structure and then
up to the pineal gland. Let's take a
look at what's happening then. So let's
say that we actually have light, light is
going to stimulate these action
potentials, so let's draw that in red. Here it's going to stimulate, let's draw,
stimulate these action potentials down
this actual axon here and then it's
going to release specific type of
chemicals onto the suprachiasmatic
nucleus that of glutamate usually. And
what it's going to do is, it's going to
trigger different types of mechanisms
inside of the suprachiasmatic nucleus.
Now, the suprachiasmatic nucleus is also
referred to as our biological clock. So
he can regulate a bunch of different
activities within our body, to regulate
our biological clock, our sleeping or
waking, you know different things like
that. Right so, what happens is he's going to
get this stimulus right and what he's
going to do is, he's going to secrete
different chemicals which can affect
multiple different nuclei. We're going to
briefly talk about these they're not
important, but the paraventricular
nucleus, will get stimulus
here, he'll come out here, down to your
lateral grey column, come out here to
what's called your superior cervical
ganglion. And then what happens is your
superior cervical ganglion, this is where
it's important. The superior cervical
ganglion has direct connections to the
pineal gland. So now I'm going to show
this in blue here, watch what happens here.
This guy's going to release specific
type of chemicals, so what do we say here.
What was the most important thing?
Light stimulates these action potentials,
stimulates the suprachiasmatic nucleus
to do different types of changes within
our biological rhythm, which stimulates
the paraventricular nucleus. The
paraventricular nucleus does what? He
sends these signals down, right? He'll
send these signals all the way down
through the lateral grey column
of our spinal cord. And from the lateral
gray column of our spinal cord, the axons
will go out to the superior cervical
ganglion. And then from the superior
cervical ganglion, these post ganglionic
motor neurons will come directly to the
pineal gland. Now, what happens here? This
superior cervical ganglion is going to
secrete some really important
chemicals. And this important chemical is
called neroepinephrine. Okay that's
interesting, right? On the actual pineal
gland, are these pinealocytes.
Because the pineal gland is made
up of pinealocytes. It has receptors
for the norepinephrine. What the
norepinephrine does, is it binds on to
this adrenergic receptor right here. So
it binds on to this adrenergic receptor.
What does it do? It triggers a bunch of
mechanisms inside of this pineal gland.
What is the overall purpose? What it does
is, you know there's what's called
tryptophan? So you have tryptophan here,
and then tryptophan can
eventually get converted into what's
called another molecule which we call
5-hydroxytryptamine. And then
5-hydroxytryptamine can get converted
into what's called serotonin. And then
serotonin can eventually get converted
into what's called melatonin. What is
norepinephrine doing? It's stimulating
these intracellular pathways to
stimulate this conversion here,
to stimulate this conversion here,
to stimulate this conversion here and
what's the overall process then?
We're stimulating the synthesis of melatonin.
Now here's where we need to get
something extremely straight here. When
this is occurring in light, this
mechanism isn't completely known to the detailed point.
But when it's in light this
pathway that we just talked about here
right? So coming from the superior
cervical ganglion here, let's follows up
these impulses coming from the superior
cervical ganglion and releasing
norepinephrine pineal gland they're
lower, so this release here is lower
during light. Okay, then in darkness, what happens?
DARKNESS everybody, darkness. It
inhibits this actual impulses right guys,
from going to the suprachiasmatic
nucleus. So then it changes different
types of rhythms and different types of
biological processes that are occurring
in the suprachiasmatic nucleus, right?
That then sends signals to the
paraventricular nucleus, to the superior
cervical ganglion. And from the superior
cervical ganglion, it goes to the pineal
gland. What's the difference here? When it
releases the norepinephrine, so it's
lower during the night, guess what? You
make higher norepinephrine during
darkness. Now here's what's important, you
have to regulate a balance because
obviously if you don't make enough of
what? If you don't make enough of this
norepinephrine, you're not going to make
enough melatonin. And if you make too
much of this this can cause problems too
right, because you have to find a happy
balance, a happy medium with this
norepinephrine right? And that's the
whole purpose here. That's what this
superc asthmatic nucleus is doing.
What is this melatonin go and do? Because
whenever this is stimulating this
pathway is actually going to be this
light pathway going  to suprachiasmatic
nucleus, paraventricular nucleus, lateral
grey column, superior cervical ganglion
to the pineal gland.  When it's
occurring in light, watch this I'm going
to show this in red. There's very little
melatonin. So very, very little melatonin
being secreted during the daytime right,
during the light. But when it's in this
darkness, all right and it
goes to suprachiasmatic nucleus, the
suprachiasmatic nucleus receives these
signals, sends it down through the
paraventricular nucleus to the superior
cervical ganglion, to the pineal gland.
and it releases more norepinephrine and
then therefore releases more melatonin.
So in darkness, look what happens to the
melatonin levels. You have higher
melatonin levels. When there's higher
melatonin levels, what does it do to the
suprachiasmatic nucleus? It acts through
different types of receptors and
stimulates the suprachiasmatic nucleus
to reset the biological clock. So what is
it going to do, it's going to reset the
biological clock. So in summation, what
can we say is the function of the pineal
gland? We can say the function of the
pineal gland is to do what? To secrete
melatonin. And what does that melatonin
do? It regulates our sleep and wake cycle
via the..? So it regulates what's called our
diurnal cycle, our sleep and wake cycle
via who, the suprachiasmatic nucleus,
which is located in the hypothalamus.
That's the whole purpose here and what's
stimulating this process of the pineal
gland to make melatonin. This is
stimulated by darkness.
So darkness is one of the primary
stimuli of the pineal gland right, via
all these actual
other signals right? But again biggest
overall concept, overall concept together
is that darkness works through
different mechanisms to stimulate the
pineal gland to release melatonin. And
that melatonin regulates your sleep and
wake cycles by acting on the
suprachiasmatic nucleus and what is the
suprachiasmatic nucleus do? It resets our
biological clock through various complex
mechanisms to help induce the actual
drowsiness and trying to get you're
getting sleepy right to be able to
induce the sleeping process, right? So
that's the purpose of the pineal gland.
Whereas in light, it inhibits the pineal
gland it releases.. So again in light,
what does it do? It inhibits the pineal
gland releases less melatonin, less
melatonin is actually not going, it's
going to affect the regulation of the
diurnal cycle via the suprachiasmatic
nucleus by how? It's going to make you
awake. So with this you would actually be
awake, versus with the darkness you would
actually have sleep, your sleepiness.
Right so sleepiness. So this is how it
does that. The pineal gland has indirect
input from the actual visual pathway and
from that input it can help to regulate
our actual sleep and wake cycles via
activating or inhibiting the
suprachiasmatic nucleus, who will then
control that by controlling our
wakefulness or our sleep fullness. Alright,
Ninja Nerds, I hope this made sense alright.
Take it easy Ninja Nerds!
