So let's have a look at the anatomy
rather than just the definitions.
Now you may have come across a
diagram like this in the past.
But here we can see we have the
brain and then descending down from the
brain we have the central nervous system.
We can see that we have
the cranial region of the
brainstem and the brain really
indicating where para-sympathetic
part of the autonomic
nervous system will arise.
We then have the cervical
aspect of the cord
We have the thoraco and
lumbar aspect of the cord.
and then we have the
sacral aspect of the cord.
And you can see that in
this thoracolumbar region in green
we have a whole series
of sympathetic nerve fibers.
We can follow these. We can
see a cell body is located
within the spinal cord.
In the actual intermedial lateral
part of the grey horn within
the thoracic lumbar parts
of the spinal cord.
And we can see its cell body
is located there and it ascends
fiber heading towards
the autonomic ganglia. Now if
we are talking about the thorax
we'd see that these would synapse in
the sympathetic chain. But for the abdomen
they pass through the sympathetic chain
they pass through the sympathetic chain
and they go directly
to the coeliac ganglia,
superior mesenteric ganglia, or
the inferior mesenteric ganglia.
And these ganglia are going to
be associated with three unpaired
blood vessels coming away from the
aorta and that's what we can see here.
In this diagram we
can see the coeliac trunk
and next to it we
have our coeliac ganglion.
We can see the superior
mesenteric artery and next to it
we can make out the
superior mesenteric ganglion.
We have the inferior mesenteric
artery and next to it we have the
inferior mesenteric ganglia.
And we can see these ganglia
coeliac, superior mesenteric,
inferior mesenteric are receiving these
These pre-ganglionic fibers.
And what happen in these
ganglia as they synapse
with a post-ganglionic fiber
and these will piggyback on
the arteries, coeliac trunk
piggyback on the arteries,
the superior mesenteric artery
and piggyback on the inferior
mesenteric artery to go to their organ.
Now again, we know
that the coeliac trunk is
going to supply the foregut
We know that the superior mesenteric
artery is going to supply the
midgut and we know that the
inferior mesenteric artery
is going to supply the hindgut.
So the autonomic ganglia
and the coeliac trunk
supplies the foregut; around the superior
mesenteric artery supplies the midgut.
The autonomic ganglia around the inferior
mesenteric artery supplies the hindgut.
So what we need to know is how
do these ganglia receive
their pre-ganglionic fibers. From what
levels of the spinal cord do these
pre-aortic ganglia receive
fibers. Because if we know that
then that will help us when we go on
to referred the pain, towards the end.
You can also see and we will explore this
later on when we get towards the pelvis,
we have the superior hypogastric plexus
down here and we will come
back to that later on.
What we can see if we go up towards the
more cranial region is that we have the
vagus nerve. We have a whole series of
other cranial nerves: oculomotor nerve
glossopharyngeal nerve, facial nerve and
these carry para-sympathetic fibers
to the head and neck structures.
We are not much worried about that.
We are concerned with the vagus nerve
passing down, you see, gives
to the heart, into the
lungs. But what you'll notice
is that this para-sympathetic,
that's passing within the vagus
nerve is incredibly long.
See it running all the way
down here and it doesn't...
it doesn't synapse with
it's post-ganglionic fiber
at the autonomic ganglia associated
with the blood vessels,
the three unpaired blood vessels.
It can pass to the coeliac plexus
superior mesenteric plexus,
inferior mesenteric plexus
but it doesn't synapse.
It passes straight through
and it only synapses when
it gets to the target organ.
Meaning the post-ganglionic fibers
of the para-sympathetic system
are very short.
They synapses within the
walls of the target organ
and we can see that here. We have the
very short post-ganglionic fibers.