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Visceral Nervous SystemVisceral Nervous System
Alex Forrest
Senior Lecturer in Forensic OdontologyForensic Science Research & Innovation Centre, Griffith University
Consultant Forensic Odontologist,
Queensland Health Pathology and Scientific Services,
39 Kessels Rd, Coopers Plains, Queensland, Australia 4108
Oral Biology
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COMMONWEALTH OF AUSTRALIA
Copyright Regulations 1968
WARNING
This material has been reproduced and communicated to you by, or onbehalf of, Griffith University, pursuant to Part VB of The Copyright Act 1968
(The Act; a copy of the Act is available at SCALEPlus, the legal
information retrieval system owned by the Australian Attorney Generals
Department, at http://scaleplus.law.gov.au).
The material in this communication may be subject to copyright under the
Act. Any further reproduction or communication of this material by you may
be the subject of Copyright Protection under the Act.
Information or excerpts from this material may be used for the purposes of
private study, research, criticism or review as permitted under the Act, and
may only be reproduced as permitted under the Act.
Do not remove this notice.
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Learning ObjectivesLearning Objectives
1. You should be able to construct a concept map of the
nervous system.2. You should understand and be able to explain the basic
structural organization of the human nervous system.
3. You should understand and be able to explain how thevisceral component of the nervous system relates to the
nervous system as a whole.
4. You should be able to explain the major structural andfunctional characteristics of the somatic and visceral
components of the nervous system.
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The visceral orautonomic nervous system includes part of both
the central and peripheral nervous systems.
Its peripheral part is concerned with the sensory and motor
innervation of viscera, glands, smooth muscle and blood
vessels.
Visceral Nervous SystemVisceral Nervous System
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The visceral systemresponds to changes in
somatic activity of the
body. Therefore the term
autonomic is notappropriate.
We use the term visceral
which describes what thesystem supplies.
Visceral Nervous SystemVisceral Nervous System
http://www.biology.eku.edu/RITCHISO/301notes2b.html
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Afferent (Sensory) Pathways
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Afferent PathwaysAfferent Pathways
Afferent = sensory
The visceral sensory pathways resemble those of somatic
nerves.
The cell bodies of the afferent neurons are located either in thedorsal root ganglia of spinal nerves or the cranial nerve ganglia.
Like the sensory somatic neurons, they do not synapse during
their passage from sensory end-organs to the CNS.
Their axons accompany those of somatic sensory neurons to
the central nervous system.
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Efferent (Motor) Pathways
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Efferent PathwaysEfferent Pathways
Unlike somatic motor pathways, two visceral neurons are
required in the visceral motor pathway, and that means that
there is a synapse in the pathway.
Therefore a ganglion will be found along any nerve carrying
visceral motor fibres to accommodate the nerve cell bodies of
the second neuron in the pathway.
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The nerve cellbodies of the
primary
(preganglionic)
neurons lie in thevisceral motor parts
of various cranial
nerve nuclei, or in
the lateral greycolumns of the
spinal cord.
From Grays Anatomy, Longman, London, 38th Edition, 1989. p 924.
Efferent PathwaysEfferent Pathways
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Their axons, which are
usually myelinated, travel
in cranial or spinal nerves
to enter the visceralganglia.
Here they synapse with
the secondary neurons.
http://www.biology.eku.edu/RITCHISO/301notes2b.html
Efferent PathwaysEfferent Pathways
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The axons of these
secondary neurons
are usually
unmyelinated, and
are distributed to
the effector organ.
http://www.biology.eku.edu/RITCHISO/301notes2b.html
Efferent PathwaysEfferent Pathways
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Efferent PathwaysEfferent Pathways
Therefore, we talk of a preganglionic neuron and a
postganglionic neuron in the motor or efferent pathway.
http://www.ualr.edu/klwennstrom/autonomic.gif
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Efferent PathwaysEfferent Pathways
Note that the sympathetic preganglionic cell is short it only
has to reach to the ganglia of the sympathetic chain.
http://www.ualr.edu/klwennstrom/autonomic.gif
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Efferent PathwaysEfferent Pathways
In contrast, the preganglionic parasympathetic cell is very long.
Parasympathetic ganglia are often located on or close to the
organ that is being supplied.
http://www.ualr.edu/klwennstrom/autonomic.gif
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Efferent PathwaysEfferent Pathways
You should note that there tend to be far more postganglionic
cells than there are preganglionic cells.
Therefore, each preganglionic neuron synapses with many (as
many as 20) postganglionic neurons.
This fact accounts for the wide diffusion of many autonomic
phenomena.
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Copyright Alex Forrest 2013
Now we have looked
at the two divisions of
the visceral system,the sympathetic and
the parasympathetic
divisions, and we have
seen the structuraldifferences between
the two.
There are functionaldifferences as well.
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http://www.biology.eku.edu/RITCHISO/301notes2b.html
The sympathetic system is
generally concerned with
the expenditure of energyand defence in
emergencies.
These are widespreadactivities which require a
diffuse distribution.
Its functions, if dischargeden masse, would be useful
to an individual in an
attitude of fight or flight.
Sympathetic DivisionSympathetic Division
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Its functions include the
elevation of the heart
rate, elevation of blood
pressure, stimulation ofbreakdown of liver
glycogen, and dilatation
of the bronchioles.
Sympathetic DivisionSympathetic Division
http://www.biology.eku.edu/RITCHISO/301notes2b.html
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Parasympathetic DivisionParasympathetic Division
The parasympathetic
system is primarily
concerned withconservative and
restorative processes such
as slowing the heart rate,
contracting the pupils toprotect the eyes from light,
and inhibiting the utilisation
of liver glycogen.
It has a restricted
distribution with more-or-
less local functions.http://www.biology.eku.edu/RITCHISO/301notes2b.html
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In general, organs
innervated by motor fibresfrom both divisions
respond to them in
opposite ways.
Through such balanced
opposition, the two
divisions coordinate
responses to widelyvarying internal and
external conditions. http://www.biology.eku.edu/RITCHISO/301notes2b.html
Parasympathetic DivisionParasympathetic Division
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Accordingly, the visceral nervous system is essential for the
preservation of internal constancy, or homeostasis.
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Sympathetic System
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The cell bodies of
sympathetic primaryefferent neurons are
located in the grey matter
of the spinal cord in the
thoracolumbar region, andsome anatomists give the
system an alternative
name for that reason:
thoracolumbar system.
Sympathetic SystemSympathetic System
http://soma.npa.uiuc.edu/courses/bio303/Image56.jpg
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Chusid, JG, Correlative
Neuroanatomy &
Functional Neurology,
Lange Medical
Publications, NY, 17th Ed,
1979, p. 140.
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Sympathetic SystemSympathetic System
http://soma.npa.uiuc.edu/courses/bio303/Image56.jpg
Sympathetic fibresare found leaving
the spinal cord only
in spinal nerves T1-
L2 and not in any
other cranial or
spinal nerves
anywhere in thebody.
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Sympathetic SystemSympathetic System
http://inside.salve.edu/walsh/autonomic_system.jpg
However, they
require to bedistributed widely in
the body, and so they
tend to travel to other
more superior andinferior spinal nerves
by spreading
themselves out along
the length of thesympathetic chain.
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The sympathetic chain is a
chain of connected gangliarunning along the side of
the vertebral column.
They contain ganglia andsynapses to connect
preganglionic and
postganglionic sympathetic
motor cells.
McMinn RMH & Hutchings RT, A Colour Atlas of
Human Anatomy, Wolfe Medical Publications,
2nd Edition, p. 196.
Sympathetic SystemSympathetic System
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Sympathetic SystemSympathetic System
Preganglionic fibres
leave the spinal cord
in the ventral root of
the spinal nerve, andpass into the
common spinal part,
and then into the
ventral ramus.
Grays Anatomy, Longman, London, 38th Edition, 1989. p 924.
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From the ventral ramus, a branch carrying myelinated
preganglionic fibres, called the white ramus communicans,
branches out to connect with the sympathetic chain.
http://publish.uwo.ca/~jkiernan/segm.gif
Sympathetic SystemSympathetic System
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When it gets to the
sympathetic chain, thepreganglionic fibres in it
can either synapse in the
sympathetic ganglion, or
they may ascend ordescend before doing
so.
This is how they pass tolevels other than T1-L2.
Grays Anatomy, Longman, London, 38th
Edition,1989. p. 1125.
Sympathetic SystemSympathetic System
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Sympathetic SystemSympathetic System
http://soma.npa.uiuc.edu/courses/bio303/Image56.jpg
Therefore, while only
spinal nerves T1-L2have these white
communicating rami,
they are able to spreadpreganglionic fibres to
every level along the
sympathetic chain
before they synapsewith secondary
neurons.
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http://publish.uwo.ca/~jkiernan/segm.gif
Ganglia in the sympathetic chain now need a method of getting
their postganglionic fibres back out of the chain and into spinal
nerves or other pathways for wide distribution in the body.
Sympathetic SystemSympathetic System
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http://publish.uwo.ca/~jkiernan/segm.gif
They do this by sending a second communicating ramus, this
time containing unmyelinated postganglionic fibres, out to each
spinal nerve.
Sympathetic SystemSympathetic System
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http://publish.uwo.ca/~jkiernan/segm.gif
This is called the grey ramus communicans, and every spinal
nerve possesses one.
Sympathetic SystemSympathetic System
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Grays Anatomy, Longman, London, 38th Edition,
1989. p. 1125.
So that sympathetic
fibres can be distributed
to all parts of the body,
the grey communicating
ramus enters the spinalnerve in the short
common spinal nerve,
and then is distributed
along both dorsal andventral rami.
Sympathetic SystemSympathetic System
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Recall that not all postganglionic fibres pass out in the grey
ramus communicans at the spinal level at which they synapsed.
Sometimes they ascend or descend several levels beforeexiting the sympathetic chain.
And sometimes, they simply pass directly to blood vessels in
the vicinity of the ganglion, rather than travelling in a grey
ramus communicans at all.
Sympathetic SystemSympathetic System
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Sympathetic SystemSympathetic System
Why do you think sympathetic fibres often travel with arteries?
Could there be a reason for this apparently eccentricbehaviour? After all, it is not the pattern followed by other
nerves
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Sympathetic System: Cranial PartSympathetic System: Cranial Part
The cranial part of the sympathetic is the bit with which we asdental and dentally-related practitioners need to be familiar.
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In the neck, the ganglia of the eight spinal nerves have been
consolidated into only three ganglia:
Sympathetic System: Cranial PartSympathetic System: Cranial Part
Represents the fused ganglia of C1C4
Represents the fused ganglia of C5 and C6
Formed by the fusion of C7 and T1.
Superior Cervical Ganglion
Middle Cervical Gangl ion
Stellate Ganglion
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Sympathetic System: Cranial PartSympathetic System: Cranial Part
Origin Unknown
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As we said before, some sympathetic fibres run in the walls of
arteries.
Sympathetic fibres run from the superior end of thesympathetic chain to form a plexus in the wall of the internal
carotid artery, called the internal carotid plexus. The
connection between this and the superior cervical ganglion is
called the internal carotid nerve.
Sympathetic System: Cranial PartSympathetic System: Cranial Part
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The internal carotid nerve begins at the cranial pole of the
superior cervical ganglion. It is therefore an ascending
continuation of the sympathetic trunk. It accompanies the
internal carotid artery through its canal into the cranial cavity
where it forms the internal carotid plexus in the wall of the artery.
Sympathetic System: Cranial PartSympathetic System: Cranial Part
Modified from:
Netter, F. 1989,
Atlas of HumanAnatomy,
Summit, New
Jersey, Ciba-
Geigy Medical,
Plate 125.
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Sympathetic System: Cranial PartSympathetic System: Cranial Part
Modified from: Netter, F. 1989, Atlas of Human Anatomy, Summit, New Jersey, Ciba-Geigy Medical, Plate 125.
It contains many sympathetic vasoconstrictor fibres, and
communicates with the trigeminal and pterygopalatine ganglia,
with II, III, IV and VI, and with the ciliary ganglion.
Sympathetic System: Cranial PartSympathetic System: Cranial Part
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The branch to the
pterygopalatine
ganglion, called the
deep petrosal
nerve,joins thegreater petrosal
nerve to form the
nerve of the
pterygoid canal.
Sympathetic System: Cranial PartSympathetic System: Cranial Part
Netter, F. 1989, Atlas of Human Anatomy, Summit, New Jersey, Ciba-Geigy Medical, Plate 127.
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Netter, F. 1989, Atlas
of Human Anatomy,
Summit, New Jersey,
Ciba-Geigy Medical,
Plate 127.
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Parasympathetic System
Parasympathetic SystemParasympathetic System
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http://www.ualr.edu/klwennstrom/autonomic.gif
Parasympathetic SystemParasympathetic System
In this system, the preganglionic fibres are usually long, with
the parasympathetic ganglion being located on, or even in, the
organ supplied. Postganglionic fibres are usually very short.
Parasympathetic SystemParasympathetic System
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Parasympathetic SystemParasympathetic System
http://soma.npa.uiuc.edu/courses/bio303/Image58.jpg
Preganglionic fibres
are limited to the
cranial and sacral
regions, a fact that
leads to thealternative name: the
craniosacral system
for the
parasympatheticsystem.
Parasympathetic SystemParasympathetic System
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Parasympathetic SystemParasympathetic System
They occur in
cranial nerves
III, VII, IX and X,
and in spinal
nerves S2-S4.
http://soma.npa.uiuc.edu/courses/bio303/Image58.jpg
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Chusid, JG, Correlative
Neuroanatomy &
Functional Neurology,
Lange Medical
Publications, NY, 17th Ed,1979, p. 141.
Parasympathetic SystemParasympathetic System
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In the cranial part of the parasympathetic system there are four
parasympathetic motor ganglia:
The Ciliary Ganglion
The Pterygopalatine Ganglion
The Otic Ganglion
The Submandibular Ganglion
Parasympathetic SystemParasympathetic System
Parasympathetic SystemParasympathetic System
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The ciliary ganglion lies in the orbit, the pterygopalatine
ganglion lies in the pterygopalatine fossa, the otic ganglion inthe infratemporal fossa, and the submandibular ganglion is
associated with the capsule of the submandibular salivary
gland.
Parasympathetic SystemParasympathetic System
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Facial Nerve (VII)
The Facial Nerve (VII)The Facial Nerve (VII)
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From Grays Anatomy, Longman, London, 38th Edition, 1989. p 1107.
Parasympathetic
fibres originate in the
Superior Salivatory
Nucleus of the
midbrain.
They emerge fromthe midbrain in the
sensory root of VII,
the nervus
intermedius, and
travel in the facial
nerve.
The Facial Nerve (VII)The Facial Nerve (VII)
The Facial Nerve (VII)The Facial Nerve (VII)
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The Facial Nerve (VII)The Facial Nerve (VII)
They continue until just before the nerve exits the stylomastoid
foramen and then leave the main nerve trunk to contribute to
the chorda tympani.
http://info.med.yale.edu/caim/cnerves/cn7/cn7_graphics/fig7_18a.gif
The Facial Nerve (VII)The Facial Nerve (VII)
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The Facial Nerve (VII)The Facial Nerve (VII)
http://info.med.yale.edu/caim/cnerves/cn7/cn7_graphics/fig7_18a.gif
This exits the skull via the anterior canaliculus for the chorda
tympani which is found at the medial end of the petrotympanic
fissure, and passes to join the lingual nerve.
The Facial Nerve (VII)The Facial Nerve (VII)
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The Facial Nerve (VII)The Facial Nerve (VII)
http://info.med.yale.edu/caim/cnerves/cn7/cn7_graphics/fig7_18a.gif
From the lingual nerve, they pass to the submandibular ganglion
where they synapse with the postganglionic fibres which are
known as the secretomotor fibres for the submandibular and
sublingual salivary glands.
The Facial Nerve (VII)The Facial Nerve (VII)
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From Grays Anatomy, Longman, London, 38th
Edition, 1989. p 1105.
( )( )
Other fibres pass tothe pterygopalatine
ganglion via the
tympanic plexus,
the greatersuperficial petrosal
nerve and the
nerve of the
pterygoid canal.
The Facial Nerve (VII)The Facial Nerve (VII)
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Here they synapse with the postganglionic fibres which are
relayed via the zygomatic branch of the maxillary division of Vto the lacrimal gland, and by branches from the ganglion to the
minor salivary glands of the nose and palate.
( )( )
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Glossopharyngeal Nerve (IX)
The Glossopharyngeal Nerve (IX)The Glossopharyngeal Nerve (IX)
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From Grays Anatomy, Longman, London, 38th Edition, 1989. p 1107.
The efferent
fibres in this
nerve pass tothe parotid
salivary
gland.
y g ( )y g ( )
The Glossopharyngeal Nerve (IX)The Glossopharyngeal Nerve (IX)
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They originate in the inferior salivatory nucleus and travel first
in IX, then in its tympanic branch which passes up through the
tympanic canaliculus in the roof of the jugular fossa.
These fibres traverse the tympanic plexus which also contains
sympathetic fibres from the caroticotympanic nerve from the
carotid plexus.
The Glossopharyngeal Nerve (IX)The Glossopharyngeal Nerve (IX)
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From Grays Anatomy, Longman, London, 38th Edition, 1989. p 1107.
They enter the
lessersuperficial
petrosal nerve
at this point, and
this nerve exitsthe temporal
bone and exits
the cranium via
foramen ovaleto reach the otic
ganglion.
The Glossopharyngeal Nerve (IX)The Glossopharyngeal Nerve (IX)
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Grays Anatomy, Longmans, London, 38th Ed 1989 p. 1105
They synapse withthe postganglionic
secretomotor fibres
in the otic ganglion
which then run inthe auriculotemporal
nerve to reach the
parotid salivary
gland.
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Vagus Nerve (X)
The Vagus Nerve (X)The Vagus Nerve (X)
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Fibres arise in the dorsal
nucleus of vagus and travelin the nerve trunk and in its
pulmonary, cardiac,
oesophageal, gastric and
intestinal branches.
These fibres are relayed in
minute ganglia which lie in
the walls of the individualviscera.
Grays Anatomy,
Longmans,
London, 38th Ed
1989 p. 1117
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The End