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Dr. G. Salter
Gross Anatomy
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Abbreviations: CNS = Central Nervous System, ANS = Autonomic Nervous System, PNS= peripheral nervous
system, ICA= Internal Carotid Artery, ECA= External Carotid Artery, GSE= General Somatic Efferent Fibers, GVE=
General Visceral Efferent Fibers, CN= Cranial Nerves, GRC= Grey Rami Communicantes
**these slides are numbered based on the order that was presented in class**
Autonomic Nervous System
I. Introduction [S2]
a. He just reordered the slides right before the lecture
b. ANS is a difficult concept.
II. Spinal Cord In Situ [S3]
a. Spinal nerves- this is a view of all of the spinal nerves.
b. Please realize if you take a cross section (what this is displaying here) through the thoracic portion of the spinal
cord and look at it, it’ll be a typical spinal nerve.
c. Because Ventral rami run in between the two ribs- these two don’t join with contiguous ventral rami.
d. The thoracic portion is a typical spinal nerve region.
e. Ventral rami, in upper cervical region, form the cervical plexus (plexus of nerves) of ventral rami extending to the
upper limbs, brachoplexus.
f. Network of ventral rami join with contiguous ventral rami to form lumbosacral plexus
III. Figure 4.5 [S4]
a. Cross section of a typical spinal nerve.
b. Please review it, there is a dorsal root, ventral root, collection of nerve cell bodies outside of CNS-ganglion
c. All sensory fibers have their nerve cell bodies collected together in dorsal root ganglion (spinal ganglion).
d. Dorsal/ventral root come together to form spinal nerves before it gives rise to a dorsal branch that supplies the
back, skin of the back, intrinsic muscles of the back.
e. All of the rest of the body is supplied by the ventral rami
f. Anterior and posterior abdominal wall- ventral ramus of the typical spinal nerve goes all the way around in a
transverse disposition.
IV. Introduction to ANS [S5]
a. Somatic Nervous System versus ANS
V. Motor Aspect of Nervous System [S6]
a. Motor is divided into Somatic and Autonomic. This is profound, we need to know this!
VI. Functional Component of Spinal Nerves: Efferent [S7]
a. GSE (autonomic part)
b. GVE (ANS)
c. These motor fibers correspond to functional component general somatic efferent
VII. Somatic Nervous System [S8]
a. Target organ is skeletal muscle- muscle that attaches to the skeleton and allow us to move.
i. Ex. biceps
ii. All of the skeletal muscles in the body are supplied by somatic nervous system
b. A single neuron is involved, unlike the ANS (has a double neuron).
c. The origin of the single neuron is CNS, specifically the spinal cord, anterior horn cells
VIII. Somatic Nervous System: 1 neuron chain: Skeletal Muscle [S9]
a. This is a cross section through the spinal cord.
b. White matter fiber tracks surrounded by grey matter full of cell bodies right in here.
c. There is an anterior (ventral horn) and posterior horn.
d. Somatic nervous system single neuron lies in the anterior horn. Then its axons proceeds out to supply skeletal
muscles, notice there is only one axon involved.
IX. CNS, PNS figure [S10]
a. Notice one is sensory and one is motor.
b. Single axon, you can follow this, going out to the skeletal muscle. This is the one we are talking about, the
somatic nervous system.
c. The anterior horn cells single neurons leads out to skeletal muscle.
X. ANS [S11]
a. Functionally divided into two parts: [S12]
i. Sympathetic Fibers- increase heart rate (Tachycardia) – for the head and neck, fibers dilate the pupil, the
smooth muscle
ii. Parasympathetic (around the sympathetic) Fibers- decrease the pulse (Bradycardia)- fibers constrict the
pupil
b. The divisions have opposite effects.
GROSS: 8:00-9:00
Scribe: Sally Hamissou
Friday, January 23, 2009
Proof: Sunita Jagani
Dr. G. Salter
Gross Anatomy
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XI. ANS- both parasympathetic and sympathetic fibers [S13]
a. Remember the target organs in the somatic system are skeletal muscle.
b. Target organs (not skeletal muscle) are glands, smooth muscle, and cardiac muscle- either one of these extend
to these particular target organs
c. Two neurons are involved and synapse is involved before the target organs are reached (target organs are
these three)
d. Origin of the first neuron is in the CNS
XII. CNS/PNS figure [S14]
a. Somatic motor system- single neuron, located here. The target neuron is the skeletal muscle.
b. Two neurons that one begins here and another begins out here somewhere
c. 2 neurons, a synapse is involved, and the target organs: gland, smooth muscle, or cardiac muscle
d. Presynaptic fiber, before the synapse, is the axon of the first neuron
e. Postsynaptic fiber, axon on a second neuron
f. First order is here and second neuron is out here (referring to the figure)
XIII. Origin of neuron # 1(cell body) for sympathetic and parasympathetic nervous system [S15]
a. Sympathetic neuron # 1 lies here for all sympathetic fibers (IMP)
i. Lies here for all of the sympathetic fibers that supply the entire body lie from T1- L2 spinal cord segments.
b. On either side of that is parasympathetic.
c. Parasympathetic- origin of the first neuron lies in the brain stem or sacral spinal cord levels S2-S4
i. There are four CN that carry parasympathetic fibers and three spinal nerves that carry parasympathetic
fibers. However, we won’t be concentrating on the latter that deals with the lower limbs of the body.
XIV.
Parasympathetic extend only to internal organs [S16,17]
a. Parasympathetic fibers extend only to internal organs
i. Viscera (thorax, neck, and abdomen)
ii. Eye (smooth muscles of the eye)
iii. Salivary Glands (in the head)
b. Subdivision of the ANS.
c. Head is involved, not periphery or the skin, but the eyes and the glands of the head are supplied by
parasympathetic fibers.
XV. Preganglionic (No. 1) and Postganglionic (No. 2): Craniosacral Outflow [S18]
a. Neuron # 1- Parasympathetic nervous system.
i. It is the cranial sacral outflow. Why? Neuron # 1 either lies within the cranium in the CNS covered by the
cranium or CNS down in the sacral portion of the spinal cord
ii. Synonymously referred to as cranio-sacral outflow. Comes from the brainstem or sacral section of the
spinal cord.
b. Brainstem is the source of neuron # 1 for the cranial part. S2-34 is the source of neuron # 1 for the sacral part.
c. Neuron 2 lies out in the periphery, we will talk about where the cell bodies lie. We will talk about
parasympathetic fibers first.
XVI.
ANS: 2 Neuron Chain [S19]
a. Sympathetic Division
b. Parasympathetic Division
i. First neuron is inside the cranium, brain stem, or sacral. Notice it has a long presynaptic fiber (before the
seconds neuron is reached) because the 2 nd order neuron lies in or near the organ supplied.
ii. 2nd order neuron lies in or near the organ supplied.
iii. Long presynaptic fiber and short post-ganglion fiber. Remember: in or near the organ supplied.
XVII. Sacral Cord Levels [S20]
a. Another view of the parasympathetic outflow from the brainstem.
b. Fibers that perform in the same function, that we mentioned a few minutes ago, arise from S2-S4 and extend to
specific spinal nerves at that point.
c. Other parasympathetic, performing the same function, run only in CN 3,7,9,10 from the brainstem.
XVIII. The Brain Stem [S21]
a. Sacral and brainstem- he is locating the second order neuron in the cranial portion of the parasympathetic
nervous system. It requires a second order neuron for synapses to occur.
b. What are the second order neurons and where are they located? And what are they called? They are collected
in bundles of cell bodies. Bunches of cell bodies outside the CNS are referred to as ganglia.
c. 4 parasympathetic ganglion of the head and neck and four is all we need to learn. Learn how to spell COPS:
i. Ciliary ganglion
ii. Otic ganglion
iii. Ptyergopalantin ganglion
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Dr. G. Salter
Gross Anatomy
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iv. Submandibular ganglion
d. COPS tells you all the parasympathetic ganglion for the CN that have parasympathetic function.
XIX.
Bottom Line [S22]
a. How many cranial nerves carry parasympathetic fibers:
i. Four- 3, 7, 9, 10
b. How many spinal nerves carry parasympathetic fibers?
i. Three- 2, 3, 4
XX. Sympathetic Nervous System [S23]
a. Fibers supply smooth muscle in the skin and they supply blood vessels all over the body.
b. There is smooth muscle in every blood vessel in the body, so sympathetic fibers have to go wherever smooth
muscles are. Therefore, smooth muscles have to supply everything.
c. Glands are found throughout the body so smooth muscles have to go to every part of the body.
XXI.
To Repeat what we said earlier, ANS [S24]
a. Whether its parasympathetic or sympathetic, target organs are the same- glands, smooth muscle, and cardiac
muscle
b. Two neurons are involved (and synapses are involved) before their target organs are reached
c. Origin of the first neuron is the CNS
d. But Sympathetic fibers extend both to the periphery (body wall and limbs) and the viscera [S25]
i. Viscera is dually innervated, parasympathetic and sympathetic fibers
ii. Brings about the various opposing functions.
iii. In periphery of the body, we only have sympathetic fibers.
XXII. CNS: Thoracolumbar outflow figure [S26]
a. 1st order neurons (of the parasympathetic fibers) lie para on either side of the sympathetics.
b. Origin arises for all of the sympathetic fibers arise from T1 to L2 of the spinal cord
c. Spinal nerves (T1-L2) receive immediately their spinal nerves, but how do the spinal nerves that rise above T1
and below L2 receive sympathetic fibers? We will talk about that soon.
d. Origin of all the sympathetic fibers of the cell body lie T1-L2. This is the thoracolumbar outflow, T1-L2.
e. Neuron 2 lies close to the spinal cord in either: the sympathetic chain or what is known as prevertebral ganglion
(we are not going to concentrate on this because those axons of those cell bodies supply the abdominal
viscera).
XXIII. Origin and distribution of sympathetic axons [S27]
a. Some is repetitious but is very important
b. Leave CNS ONLY between T1 & L2 (thoracolumbar outflow). From lateral horn cell bodies, pre-ganglionic
axons pass into the ventral root, collect in spinal nerve, and connect to the sympathetic trunk ganglia via white
rami communicantes.
c. In other words via the communicating branches that are white in appearance because of the myelin sheath
around the nerve fibers. Myelin appears white in a fresh section.
XXIV. Spinal Nerve figure [S28]
a. Origin of the fibers arise in cell bodies located in the lateral horn.
b. Axons from the cell bodies (T1-L2) supply sympathetic fibers to all spinal nerves.
c. How do they do that? This is anywhere from T1-L2- the axon enters the ventral root, passes into the spinal
nerve T1-L2, the axons (presynaptic/preganglionic) comes in and connects to the sympathetic trunk via a
communicating branch (white ramus communicantes)- white having myelin.
d. GRC (fibers) is a communicating branch from the sympathetic trunk to the spinal nerves.
e. GRC (all grey rami) fibers have postsynaptic fibers in them and don’t have any myelin sheath- why we use the
term grey.
i. It only contains postsynaptic fibers.
XXV. Then the fibers, once in sympathetic trunk [S29]
a. Once the fibers reach the sympathetic trunk, the fibers must synapse in either paravertebral ganglion or
prevertebral ganglion.
b. Paravertebral Ganglion- sympathetic trunk ganglion, sympathetic trunk lies on either of the vertebral column
hints the term paravertebral.
XXVI. Thoracoabdominal Nerves [S30]
a. This is a sympathetic trunk on either side
b. Sympathetic fibers come in, arise, and enter the sympathetic trunk, and the fibers can either synapse in
sympathetic trunk or go somewhere else, we are interested in the ones that synapse in the sympathetic trunk
c. Sympathetic trunk with two connections (communicating branches) to spinal nerves is rami communicantes:
White (lateral) & Gray (medial)
d. Presynaptic fibers run in the white because they still have the myelin sheath.
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Dr. G. Salter
Gross Anatomy
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e. [S31] (look at the green line in the figure) The origin is in the lateral horn, axons enter the ventral root, enters the
spinal nerve, passes through the white ramus communicantes, into the sympathetic trunk, and then a synapse
occurs, as is depicted in the figure.
i. This is one example of where the second order neurons lie. Once they get into the sympathetic trunk they
can either synapse at that level or pass through.
ii. This is a paravertebral sympathetic trunk ganglion, a sympathetic fiber reaches a sympathetic trunk and a
synapse occurs.
f. [S32] Second option is that presynaptic fiber can take the same origin, same ventral route. The white rami
communicantes pass through the ganglion to connect as presynaptic fibers over here. Fibers don’t synapse,
they pass through the ganglion and synapse on the fibers called prevertebral ganglion. These axons supply the
abdomen but we aren’t concerned about those particularly.
XXVII. Prevertebral or Preaortic Ganglion of Abdomen [S33]
a. Prevertebral- abdomen, posterior abdominal wall, prevertebral ganglion or preaortic ganglion.
b. Presynaptic fibers pierce the diaphragm and synapse on the lower (more inferior) prevertebral (before you get to
the vertebrae if you approach the vertebrae anteriorly) or because the aorta lies against the vertebra they are
preaortic.
c. We aren’t concerned about those particularly.
XXVIII. Sympathetic fibers extend both to the periphery and viscera [S34]
a. Sympathetic fibers extend both to the periphery (body wall and limbs) and to the viscera. The viscera is dually
innervate
XXIX. Fundamentals [S35]
a. 31 percent of spinal nerves supply the entire surface of the body we call the dermatome patterns.
b. Smooth muscles exist in every blood vessel inferior to the cranial fossae and at the base of every hair follicle in
the body. There are certain glands all over the body.
c. Glands exist everywhere on the body surface
d. Therefore sympathetic fibers reach every square inch of the body surface in the periphery- including the face
i. Accomplish this by communicating with every spinal nerve. Every spinal nerve goes to a specific region of
the body
ii. Every spinal nerve has to have sympathetic fibers in it.
XXX. Big Picture Sympathetics [S36]
a. Sympathetic distributions everywhere both to the periphery (body wall and limbs) and to the viscera
b. All sympathetic fibers must enter the sympathetic chain
c. Sympathetic fibers use paravertebral chain ganglion to synapse in and to distribute both to the periphery or
viscera by using the paravertebral they can stay there or synapse in the viscera
i. Peripheral- fibers must extend into the sympathetic trunk into each of the spinal nerves by one or two
means:
1. Synapse in chain at same level and follow GRC to spinal nerve at that level. Applies to T1-L2
nerves. But how do you reach spinal nerves superior to T1 or inferior to L2?
2. Enter chain, then extend up/down, synapse, and then follow GRC to spinal nerves at that level
(which is a different level from that of the entry point—T1-L2)
ii. Viscera
d. (Therefore), the only function of GRC (postganglionic no myelin) is to carry postsynaptic fibers to every spinal
nerve and therefore to the periphery (body wall and limbs).
e. Question: clarification on # 2 inter chain- sympathetic chain paravertebral ganglion are located in the
sympathetic trunk or sympathetic chain.
f. Question- clarification on grey rami- is it only in the vertebral section in t1-l2? Answer: Every spinal nerve
receives sympathetic fibers and that’s the way they get there, they proceed through the GRC.
XXXI. Sympathetic fiber to the periphery [S37]
a. Anywhere superior to T2
i. First option, here is the origin of all sympathetic fibers. Arise at the lateral horn, that’s where the cell bodies
lie. Axons proceed into the ventral root into the spinal nerve, and via a white rami communicantes, into a
sympathetic trunk/chain or paravertebral ganglion
b. T1 to L2
i. Synapse post ganglion fibers will follow the GRC into the spinal nerves, T1-L2.
c. Inferior to L2- superior to T1
i. Fibers will descend and follow the same pathway and instead of synapse at the same level, they would
descend presynapticly and synapse at levels inferior to L2 and then connect to every spinal nerve inferior
to L2 by way of GRC.
d. What if they are trying to reach spinal nerve superior to T1.
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Dr. G. Salter
Gross Anatomy
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i. Fibers will pass through (T1-L2’s only origin) the sympathetic trunk, fibers destined for spinal nerves
superior to T1 will enter sympathetic trunk and ascend to synapse in sympathetic ganglion superior to T1.
In order to connect to all cervical spinal nerves, they would do so by way of GRC.
e. Every sympathetic fiber in the periphery reaches all spinal nerves at the level, above the level, or below the level
of entry
XXXII. To Periphery Below Head Fig. 4.12 [S38]
a. Sympathetic fibers arise from T1-L2- this shows the supply of sympathetic fibers to the periphery.
b. First order neurons lie between T1-L2.
c. Axons proceed out to enter the sympathetic trunk. They can either synapse at the level of entry and enter the
spinal nerve, or they can descend and enter spinal nerves inferior to L2 or ascend and enter spinal nerves
superior to T1.
d. This is how sympathetic fibers reach all the spinal nerves and supply peripheral below the head. We are
interested in the head and neck.
XXXIII. Overview of Sympathetics to Head [S39, 40]
a. Superior trunk is shown, on either side paravertebral located.
b. These upper fibers that proceed from the upper portion of the thoracic spinal cord segment , for ex. T1-T5 or T4,
enter the sympathetic trunk and in order to get to the smooth muscles of the head and the skin of the face, these
fibers would ascend and synapse on these ganglion, perhaps only superior cervical ganglion, 1 2 3, this is the
most superior one.
c. Postsynaptic fibers proceed from that out to the skin of the face, the smooth muscles of the eye, submandibular
and sublingual gland, and the parotid gland.
XXXIV. [S41]
a. Originally, there were 8 cervical sympathetic ganglia, one associated with each cervical spinal nerve.
b. 12 thoracic sympathetic ganglia associated with every thoracic spinal nerve. So it makes sense, that they were
8 cervical ganglia when we were developing.
c. But these ganglia coalesced into 3 (4) ganglia. Therefore, these remaining cervical sympathetic ganglia were
left to send postsynaptic fibers (via GRC) to several spinal nerves each.
XXXV. Sympathetic Trunk Figure [S42]
a. What happens here, the sympathetic trunk is located posterior to carotid sheath on the prevertebral fascia. –
b. In the carotid sheath is the carotid artery
i. We will be doing this dissection later on because it’s deeper in the neck. This is where the sympathetic
trunk is located.
c. Thoracic ganglion- here is the sympathetic trunk in the thoracic region, 12 of them.
d. In the cervical ganglion, its 1,2, 3 (usually 3)
i. The fibers that reach the cervical ganglion come from this region, enter the sympathetic trunk, ascend in
the trunk and synapse. The postganglionic fibers (post synaptic) reach every spinal nerve by way of GRC.
ii. Even though there are fewer sympathetic trunks than sympathetic ganglion, each ganglion sub-serves
several spinal nerves.
e. Right common carotid artery
i. Internal and external carotid artery, we are going through this fast because this will be shown to us many
other times.
ii. Hyoid bone is shown.
f. Inferior cervical ganglion- ganglion sub-serves CN 7 and 8, by sending GRC to them.
g. Middle cervical ganglion- GRC going out to 5 & 6 spinal nerves, and in the cervical region the ventral rami join
together.
h. Superior cervical ganglion- superiorly located, it supplies the upper 4 spinal nerves with GRC.
i. If a surgeon goes in and cuts the GRC to the ventral rami (spinal nerves) what affect would that have? (remember
target organs are glands and smooth muscles)
i. Glands would secrete less
ii. Blood vessels (surrounded by smooth muscle)- if you cut out the sympathetic input, they dilate. For older
people that would need to improve circulation, surgeons would cut the GRC to dilate the vessels and
provide more heat. Old people always complain about being cold.
j. A dental student, that came into his office, couldn’t hold onto the instruments (had hyperhydrosis in the hands).
i. The surgeons cut the GRC to the 7th and 8th nerve, it cut the innervations of the sweat glands and the
sweat dried up-functional significance.
XXXVI. Sympathetic fiber to the head would ascend as.. [S43]
a. Sympathetic fibers to the head would ascend as presynaptic fibers to reach the most superior cervical
sympathetic ganglion. This is how sympathetic fibers reach the head and not the neck. Synapse would then
occur in superior cervical ganglion, and postsynaptic fibers would follow the arterial branches (ECA & ICA) to
GROSS: 8:00-9:00
Scribe: Sally Hamissou
Friday, January 23, 2009
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Dr. G. Salter
Gross Anatomy
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reach the smooth muscle and glands of the head. Two large branches (at least one) off the superior cervical
ganglion are referred to as the ECA and ICA nerves
XXXVII. Figure of head and neck [S44]
a. Ascending fibers in order to reach the head, synapse in superior cervical ganglion, synapse occurs and
postganglionic fibers follow blood vessels that go everywhere. This is the pathway that the postsynaptic fibers
take to reach the every organ.
b. Common carotid, ECA, ICA, and here’s the superior cervical ganglion.
c. Presynaptic fibers ascend in the sympathetic trunk and in order to go to the periphery, they follow the spinal
nerves to the periphery. In order to go the head, they synapse here and postganglionic fibers follow the ICA
nerve, and the nerve forms a plexus around the artery and goes everywhere the artery goes, again these are
postsynaptic sympathetic fibers.
d. Or these postsynaptic fibers can run with the ECA nerve and follow the ECA and it’s eight branches to supply
the smooth muscles and glands in the head.
XXXVIII.
Overview of sympathetic to head [S45]
a. Lateral horns of cord levels T1-2- that’s the origin of all of them
b. Preganglionic fibers enter the sympathetic trunk
c. Preganglionic axons ascend in the sympathetic trunk
d. Fibers pass through the inferior/middle cervical ganglion to the superior cervical ganglion, synapse occurs, and
postganglionic fibers distribute via the ICA and ECA nerve to the specific arteries. The carotid nerves form
plexus around the arteries. These fibers pass to their target organs via the smooth muscle in blood vessels
walls, or dilator pupillae muscle in the eye or sweat glands. These are the target organs of the sympathetic
fibers.
e. Functions
i. Vasoconstriction, dilate pupils, stimulate sweat glands
ii. No sympathetic fibers, the blood vessels would dilate. No sympathetic fibers (pupils will constrict)
XXXIX. Sympathetic fibers to the head [S46]
a. Fibers arise T1-L2, cell bodies enter the spinal nerve at the upper thoracic portions, pass through the white
communicating branch into the sympathetic trunk. The fibers do not synapse but ascends to the superior
cervical ganglion and then synapses.
b. Sympathetic fibers to the head ascend in the sympathetic trunk and synapse in the superior cervical ganglion &
then postganglionic fibers follow the ECA & ICA to reach the target organs
XL. Now lets consider the Cervical Viscera [S47]
a. Cervical viscera: Pharynx, trachea, parathyroid, thyroid gland. All are viscera in the neck.
XLI.
Sympathetic fibers to the neck viscera.. [S48]
a. Sympathetic fibers to the neck viscera (as in pharynx) would ascend as presynaptic fibers (stop in the cervical
region) to reach the cervical sympathetic ganglia. Synapse would then occur, and postsynaptic fibers would
pass to the viscera via direct branches or via the blood vessels. The fibers don’t run with the spinal nerves to
serve the periphery.
b. We may find superior thyroid artery today in lab, it has sympathetic fibers around it to reach thyroid gland
XLII.
Cervical Viscera [S49]
a. Instead of going to the head, the fibers ascend to the cervical sympathetic ganglion (any of the three), synapse
occurs, and the fibers follow a direct path to the viscera of the blood vessels.
XLIII. Questions? [S50]
[End 43:09]