+ Why doesn’t C2 supply the superior cervical ganglion? – November 05
Hello John,
I am having a lot of trouble getting a visual, 3-D
sense, of the sympathetic chain. Particularly
nerve supply. For example, why isn’t the superior
cervical ganglion supplied by C1 or 2?
Any help would be appreciated.
M.L.
Sydney.
>>>MY COMMENTS:
The most helpful thing you can do if you are
having trouble getting, as you say, a 3-D, sense
of some part of anatomy is to make a 3-D model of
it. Make your model out of anything you like.
You don’t have to be good at crafts and it doesn’t
have to look pretty. You will learn a lot from
putting the pieces together.
So while you go off to collect egg boxes and
pipe cleaners, here’s something I prepared
earlier.
Think of the sympathetic division of the
autonomic nervous system like two highways, one on
either side of a long suburb called ‘Spinal cord
T1 – L2’.
Nerves impulses leave the suburb and go onto
the highway via ‘On’ ramps and exit the highway
via ‘Off’ ramps.
‘On’ ramps are called White communicantes.
‘Off’ ramps are called Gray communicantes. The
white ones are white because they have a myelin
sheath.
So just like any highway, you enter at one
point, travel along for a while and then exit at
another point. Nerve impulses in the sympathetic
chain are no different. They enter the
sympathetic chain at one vertebral level and exit
at another.
Now along these twin highways are service
stations. Places where you can get out and
stretch your legs, change cars if you like or
split yourself in four and drive off in four
different cars going in different directions.
No hang on, that was a dream I had last night.
It may be stretching the analogy but it is what
nerve impulses do. The service stations are the
paravertebral ganglia that make up the beads in
the chain. At these service stations (ganglia)
nerve impulses may change cars (synapse) and
continue on their way in a new car (nerve).
or they might drive off in four different cars
in four different directions along axon
collaterals (branches).
Now here’s the bit I think you’re getting stuck
on. Remember the suburb all the nerve impulses
live in?
Humour me.
It’s called ‘Spinal cord T1 – L2’
The sympathetic division may supply all parts
of the body but it only emerges from the spinal
cord and so only penetrates the dura between T1-
L2.
So it makes sense that there are more ‘Off’
ramps (gray communicantes) than ‘On’ ramps (white
communicantes).
14 ‘On’ ramps and 31 ‘Off’ ramps to be exact.
Each highway usually has 22 service stations
(paravertebral ganglion) but instead of them being
called, ‘the servo that has a McDonalds’ or ‘the
one that has KFC’, they’re called cervical,
thoracic, lumbar and sacral ganglia.
and not a big Mac in sight.
You want a coke with those fries or are you
still with me?
Good.
Now that you have a new found understanding of
the structure of the sympathetic chain . . .
just nod . . . it’s time for some audience participation.
The superior cervical ganglion is located
posterior to carotid artery and anterior to
transverse process of C2, right? Keep nodding.
At what level of the spinal cord do the
sympathetic nerves emerge that supply the superior
cervical ganglion?
That’s correct! T1 or below.
and the middle cervical ganglion?
Correct again! T1 or below.
Now, you’ve got it. Well look, we could chat
about this all day but you’ve got a model to make.
The significance of all this tomfoolery is that
if the sympathetic chain is compressed anywhere it
can have the effect of switching on the whole
sympathetic chain. Not good.
This can put you in constant ‘fight or flight’
mode. Making you fearful and agitated with poor
digestion and lousy sleep. You’ll be sensitive
to bright lights because your pupils are locked
open and you’ll have excess adrenalin in your body
which has a long term corrosive effect on your
nervous system.
Whadaya mean reading my response has had the
same effect?