- Parasympathetic fibers.
The anatomy of the
parasympathetic nervous system
is more straightforward.
There's a little bit of review.
Do you remember--okay.
Parasympathetic, what do you
notice about my green fibers?
Green fibers are coming
from where, my friends?
They are coming from the brain
and they are coming
from the sacrum.
So, S2 to S4 and cranial nerves.
What?
Cranial nerves who?
What cranial nerves carry
parasympathetic fibers?
Three to make
your pupils constrict.
Seven--
oops, seven goes like that.
That's a seven.
Sure, it does.
To make you salivate and cry.
Nine to make you salivate
some more, and 10,
holy-to-do-everything-else.
What cranial nerve was 10?
That was the vagus nerve
and it comes down
like this and goes everywhere.
The vagus nerve does 75
to 80 percent of all of your
parasympathetic innervation.
It's actually carried
in the vagus nerve,
which is wildly fantastic.
The rest of your cranial
nerves carry some of it,
and then you've got
some sacral nerves that are
carrying some of it.
And what is the anatomy?
What is the spinal cord anatomy?
It's not this.
And it's not this.
In fact, it'll be this, except
what am I going to cross off?
Who needs this?
Hum, that's going to be in
the sympathetic nervous system.
We're not even-- it--
just pretend like that doesn't
exist for parasympathetic.
So if we were going to map this,
map our dark green pathway,
where is our
pre-ganglionic cell body?
The same place as all of our
other visceral motor.
It's in either the lateral
grey horn,
or, like, the lateral arena.
I think, technically,
in the sacral spinal cord,
they don't call it
a lateral grey horn,
but they do
have a lateral grey area.
And then, of course,
in the cranial nerves
the visceral motor fibers are
coming out of the brain.
So, they're not going to have--
I mean, we're not mapping it
onto the spinal cord at all,
because it's
coming out of brain.
But in the sacral region,
for the areas that do map, we've
got this parasympathetic fiber
that comes through just
like everybody else.
It comes through the ventral--
I mean, the anterior root
through the spinal nerve,
out the anterior ramus,
and then, remember,
this guy is so long,
and this is my
pre-ganglionic neuron.
And it's still--
let's just depend.
It actually doesn't
go to the heart.
It's the vagus nerve
that goes to the heart.
But we're just going to pretend,
because, you know,
pretending is fun.
And I'll change my color
just slightly.
We'll make it
a little bit darker.
This is my ganglionic neuron
with parasympathetic fibers,
the ganglia,
the ganglionic
neurons are really short.
They're often embedded in
the wall of the effector itself.
Again, the heart is innervated
by the vagus nerve.
So, we're not going to see this
coming out of the spinal cord,
but we would see a pre-ganglion
neuron that's really long
coming out of the brainstem,
where cranial nerve 11 exits
the brain--
I mean, 10, because that's
the vagus nerve.
Oh, what's true
about my pre-ganglion neuron?
Okay.
I love you guys a lot,
and I really want to put
the yellow ruffly pants
on this pre-ganglion neuron,
but it's really long.
Really, long.
Look at me.
I'm doing it, anyway.
Go. Okay.
We have a little bit
of wonkiness in my--
oh, look.
I did it.
It's totally myelinated.
Is my ganglionic
neuron myelinated? No.
And that's a characteristic
of my visceral motor pathways.
What else do you need to know?
It's going to calm us down.
We're going to chill out.
We're going to be able
to make babies,
unless we're sea urchins,
but sea urchin don't have
spinal cords, so we're cool.
That's it.
Are you happy?
Okay.
Now we're going to review
all of it together,
and I will be right
back to do that.
