the distribution of the sympathetic nervous system we talk about it as being thoracic
because the cell bodies of origin are in the intermediolateral cell column between T 1 and
L 2 and that's pictured here so this is about T 1 and this is about L 2 the sympathetic nervous
system is distributed in every part of your body head neck thorax abdomen pelvis and your limbs
because you have blood vessels in your limbs that are going to be regulated by your sympathetics
you will also notice that we have even though the cell bodies of origin are restricted our ganglia
are not so we have ganglia that go all the way down here almost into the pail actually into the
pelvis and we have ganglia that go all the way up into our neck the superior cervical ganglia
is all the way up right next to the bifurcation of your carotid artery from common carotid to
internal and external so what happens is these pre ganglionic neurons send their axons out
sometimes they synapse at the same level and for example a pre ganglionic neuron down here around
l2 could come into the cord and then its axon could go all the way down to the last ganglia
before it synapses and that so it could synapse here and then distribute or again from somewhere
like t1 this neuron could go all the way into the chain and go all the way up and synapse in
the ganglia that is the superior cervical so the distribution of the sympathetic chain goes beyond
the distribution of the intermediolateral cell column and that's because these axons can travel
within the chain up or down a level or two or maybe even many levels to get to a ganglion
that's eventually going to get to a more distal target we even have a special classification for
the abdominal viscera these nerves are called splanchnic nerves and kind of like pelvics
you'll see this term again when we talk about the parasympathetics and you think about pelvic
splanchnic nerves the sympathetic splanchnic nerves are nerves that come from areas they're
their pre ganglionic neurons are in the intermedia lateral cell column just like all the others and
instead of synapsing in the chain they bypass it and synapse in what we call a pre vertebral pre
vertebral ganglion these are unpaired
you'll note that the sympathetics are paired all the way down the pre vertebral are unpaired and
they're the reason they're called pre vertebrals they're they're more anterior so if you draw
in the vertebral bodies kind of along here these would be in front of the spinal cord
and we can see that our sympathetic chain lies beside the bodies and so that's para vertebra
vertebral para beside pre vertebral ganglia are in front and they're down here along the aorta
and they're right next to the origins of the great vessels the celiac trunk the superior mesenteric
artery the inferior mesenteric artery so those ganglia this one's bad I'm gonna redraw this
so if I redraw my vertebral bodies and then in front of it kind of go stood in front here
would be my aorta these neurons come out bypass the ganglia and synapse and what is called a pre
vertebral ganglion those axons so those come together and form the splanchnic nerves these
ganglionic neurons follow the blood vessels to get to their targets so it's really easy to see
how things in the thorax get to where they're going because there are ribs here and these
sympathetic neurons just come out and distribute and rejoin they rejoin the spinal nerves that are
going around the edges ribs the splanchnics come out synapse in ganglia that lie along the
aorta and then instead of rejoining nerves they actually just follow the blood vessels
to all of their targets and again those targets are going to be abdominal targets so everything
below the diaphragm below the ribs so the entire digestive system and everything also in the pelvis
all of the reproductive organs are going to be innervated by these splanchnic nerves and here
is what the sympathetic look like in the chain so here we have a chain ganglion they kind of look
like beads on a string here's the entire chain here here are the spinal nerves coming out and
going up or down synapsing and then rejoining the spinal nerve here right here we can see the
examples of some of these splanchnic nerves so axons have come out they've bypassed and their
axons are still going and they're going to head down here this is the dome of the liver they're
gonna head down behind this dome of the liver they're gonna go through the diaphragm they're
gonna synapse in great big ganglia that lie along the aorta at the origins of the great
vessels we can also see in this image this is the phrenic nerve which has been pulled
aside and remember that's part of your cervical plexus and it's going right down to the diaphragm
here which is domed over the top of the liver here's our esophagus and here's the aorta so
in summary what do I want you to know about the sympathetic nervous system with regard to the
preganglionic sympathetic neurons where they found what's their neurotransmitter and are
their axons long or short where will you find the sympathetic chain ganglia and then with regard to
the ganglionic neurons where are they found what's their neurotransmitter and are their
axons long or short if you understand all of these concepts you're ready for the assessment