T3 - Neurology
Oct. 24, 2003
Dr. Laura McNeilly
Post ganglionic Neurons
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Cell bodies from the sympathetic ganglia
Sympathetic ganglia found in 2 locations
1. Sympathetic Chain, aka trunk
 C1 -= coccyx
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3 pairs of cervical ganglia
 12 “ “ thoracic “
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5 “ “ lumbar
“
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5 “ “ sacral
“
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1 coccygeal ganglion
 51 Total ganglia
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axons are unmyelinated
axons have 2 options:
a) exit sympathetic ganglia forming the gray ramus, and reconnects with a spinal nerve
proximal to branching of anterior and posterior rami. These neurons will travel with a
spinal nerve and supply sympathetic innervation to structures in skin and body wall.
Both anteriorly and posteriorly.
** all spinal nerves receive gray rami.
b) exit the sympathetic ganglion and travel with blood vessels to innervate other
structures (organs, glands) ABOVE DIAPHRAGM.
2. Prevertebral Ganglia
 A group of 3 ganglia located along the abdominal aorta named for the major unpaired
branches of aorta (Celiac, superior and inferior mesenteric)
Cervical Sympathetic Chain
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3 pairs of cervical sympathetic ganglia
1. Superior ganglion
2. Intermediate ganglion
3. Inferior ganglion
4. [ sometimes a 4th called Cervicothoracic ganglion aka: Stellate ganglion]
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Superior cervical ganglion
 Located anterior to C1, posterior to jaw
 Gives off gray rami to cervical nerves C1 – 4
 Gives off fibers which follow Common Carotid Arteries and their branches to supply anterior
brain and face.
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Intermediate Cervical ganglion
 Gives off gray rami to CN C5 and C6
 Gives off fibres which follow Vertebrobasilar system to supply posterior brain
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Inferior Cervical ganglion
 Gives off gray rami to CN C7 and C8
 Gives off fibers which follow Vertebrobasilar system to supply posterior brain
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Both intermediate and inferior ganglia give off small #’s of fibers which go to thoracic structures.
Thoracic Sympathetic Chain
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Consists of 12 pairs of ganglia
Each ganglion receives preganglionic fibers from associated nerve root via White Ramus.
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Each receives fibers which pass up or down the chain one or more levels.
Each ganglion gives off a gray ramus which connects to its associated spinal nerve.
Additionally:
T1 – T4:
gives off fibres which supply organs and glands of thorax (heart, lungs).
These fibers follow the aorta and its branches.
T5 – T9:
have Preganglionic fibers which pass through w/o synapsing and collectively form the GREATER
SPLANCHNIC NERVE, Which ends in a Prevertebral ganglion. (preganglionic nerve starting from
ant/lat horn of SC)
T10 – T11: have preganglionic fibers which pass through without synapsing forming the LESSOR SPLANCHNIC
NERVE, which ends in a prevertebral ganglion.
T12:
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has preganglionic fibers which pass through without synapsing forming the LEAST SPLANCHNIC
NERVE. Which ends in a prevertebral ganglia.
Splanchnic nerve and their post ganglionic fibers supply the abdominal organs.
** end of 10/24 notes, begin 10/31 notes **
Lumbar Sympathetic Ganglia
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5 ganglia
each ganglia gives off a gray ramus to its associated spinal nerve
Additionally
L1 – L2:
receive preganglionic fibers from associated spinal nerve via White Rami
Have preganglionic fibers which pass through without synapsing and collectively form the LUMBAR
SPLANCHNIC NERVE which will end in a prevertebral ganglion.
L3 – L5:
receive preganglionic fibers from T11 – L2 which pass down the chain.
Sacral Sympathetic Ganglia
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5 ganglia
receive preganglionic fivers from T11 – L2
each ganglion will give off a Gray ramus to its associated spinal nerve
Coccygeal Ganglion
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aka: Ganglion impar
both (R + L) sympathetic chains unite at this point
anterior to coccyx
receives preganglionics from T11 – L2, and gives off a gray ramus to its associated spinal nerve.
Clinical Note:
 due to the location of the ganglion, injury to the coccyx can lead to:
o pushing of filum terminale leading to laxing of spinal cord and potential for nerve root damage.
o Irritation of the ganglion leading to aberrant sympathetic output.
 Some correlation between coccygeal injuries and PMS, endometriosis, constipation, etc.
PREVERTEBRAL GANGLIA
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aka Collateral Ganglia, aka Paravertebral Ganglia
3 ganglia located on anterior surface of abdominal aorta, in association with the 3 major unpaired trunks of
aorta.
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mesentery – conn. tiss. That hold the organs to the body wall.
1. Celiac Ganglion
 Receives preganglionic fibers from T5 – T10 via Greater and Lesser Splanchnic nerve.
 Post ganglionic fibers follow the celiac artery and its branches to supply the liver, gallbladder, stomach,
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pancreas, spleen, kidneys, adrenal glands.
Plexus that follows the artery is called CELIAC PLEXUS, aka SOLAR PLEXUS.
Some preganglionic fibers which passed through the sympathetic chain also passed through the Celiac
ganglion w/o synapsing, these fibers travel to the adrenal medulla and synapse there.
2. Superior Mesenteric Ganglion
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receives preganglionic fibers fromT10- T11 via the LESSOR SPANCHNIC NERVE
post ganglionic fibers follow the superior mesenteric artery to supply the small intestine, proximal large
intestine up to splenic flecture.
3. Inferior Mesenteric Ganglion
 Receives its preganglionic fibers from T12 – L2 via the Least and Lumbar Splanchnic nerves
 Post ganglionic fibers follow the inferior Mesenteric artery to supply distal colon, bladder, genitalia.
ARDRENAL MEDULLA
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Cells are embryologically nervous tissue.
These cells are the “POST GANGLIONIC NEURONS”
BUT they release their NT’s into the bloodstream vs. a synaptic cleft,  cells are considered glandular and NT
is called a HORMONE.
A NT that is secreted into the tissues via a synapse remains active for only a few seconds before it is:
a). broken down
b) recycled
c) diffused away
Hormones are released directly into the blood stream, these remain active much longer (10s – several
minutes) and are broken down in the liver (usu.)
Hormones released from AM = NOREPINEPHRINE AND EPINEPHRINE
Clinical Note:
1.
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stimulation of AM causes release of hormones which have sympathetic effect in the body (like sympathetic
nervous innervation) but effect is greatly prolonged. (lasts longer)
organs/glands redeive dual sympathetic stimulation reflecting importance of sympathetics for survival.
2.
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having the AM involved in sympathetic allows for sympathetic access to every cell in the body.
Substances which stimulate adrenals:
a) caffeine (and related xanthines)
b) perceived stress
NEUROTRANSMITTERS IN ANS
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this applies to para/sympathetic NS in the ANS
A) all parts of the peripheral NS (somatic and autonomic) include:
Preganglionic sympathetics,
Pre/Post ganglionics
Parasympathetics
Somatics
They all release:
ACETYLCHOLINE
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there are 2 kinds of cholinergic receptors (receives Ach)
1. muscarinic: btwn post ganglionics and effector cells
2. nicotinic:
btwn pre/post ganglionic and at neuromuscular junctions (NMJ)
B) Postganglionic sympathetic neurons release: NOREPINEPHRINE
EXCEPT:
1. sympathetics to sweat glands release Ach
2. norepinephrine is converted to EPI in the Adrenal medulla
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adrenergic receptors are further divided into ALPHA AND BETA
Clinical Note: “beta blockers” – drugs that block beta receptors of the heart which blocks sympathetic innervation
of the heart.
** end of 10/31 notes **