The autonomic nervous system
• Introduction: visceral, or vegetative, apart of N.S.
distributed in the viscera, cardiovascular system &
secretory glands.
• Compositions:
1. Visceral sensory nerve
2. Visceral motor nerve
3. Centers of visceral nerves
• The visceral motor nerves:
2 parts: sympathetic and parasympathetic nerves
Marong Fang, PhD.
Institute of Anatomy & Cell Biology
Somatic
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vs.
Autonomic
Voluntary
Skeletal muscle
Single efferent neuron
Axon terminals release
acetylcholine
Always excitatory
Controlled by the
cerebrum
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Involuntary
Smooth, cardiac muscle;
glands
Multiple efferent neurons
Axon terminals release
acetylcholine or
norepinephrine
Excitatory or inhibitory
Controlled by the homeostatic
centers in the brain – pons,
hypothalamus, medulla
oblongata
Marong Fang, PhD.
Institute of Anatomy & Cell Biology
Marong Fang, PhD.
Institute of Anatomy & Cell Biology
Main differences between somatic motor and visceral motor n.
Somatic
Visceral
Effectors
Skeletal
muscles
Cardiac, smooth muscles and
glands
Kind of fibers
One
Two: sympathetic and
parasympathetic
From lower
center to
effect require
Single
neuron
Two neurons: preganglionic
neuron (fiber) and
postganglionic neuron (fiber)
Fibers
Thick
myelinated
Distributive
form
Nerve trunk
Nerve plexuses
Control
Voluntary
Involuntary (unconsciousness )
(consciousness)
Preganglionic: thin myelinated
postganglionic: unmyelinated
Autonomic Nervous System
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2 divisions:
 Sympathetic
 “Fight or flight”
 “E” division
 Exercise, excitement,
emergency, and
embarrassment
 Parasympathetic
 “Rest and digest”
 “D” division
 Digestion, defecation,
and diuresis
Marong Fang, PhD.
Institute of Anatomy & Cell Biology
 The sympathetic nervous system:
1. lower center: in lateral horn of T1(or C8) ~ L3
segments of spinal cord
(intermediolateral nucleus)
2. peripheral part: sympathetic trunks
sympathetic ganglia(pre/para-vertebral)
sympathetic plexuses
sympathetic nerves
communicating branches
Marong Fang, PhD.
Institute of Anatomy & Cell Biology
 The sympathetic trunk:
--- paravertebral ganglia and interganglionic branches
--- extends from the base of skull to the coccyx
--- on the both sides of vertebral column
--- 5 parts: cervical part (superior, middle and inferior cervical
ganglia)
thoracic part (10~12 pairs of thoracic sympathetic
ganglia)
lumbar part (3~4 pairs of lumbar sympathetic ganglia)
sacral part (4~5 pairs of sacral sympathetic ganglia)
coccygeal part (1 unpair of coccygeal ganglion)
Marong Fang, PhD.
Institute of Anatomy & Cell Biology
 The sympathetic ganglia: 2 types
---- paravertebral ganglia:inf./sup./imf. Cervical
ganglia;12 thoraci,3-4lumbar,4-5sacral,coccygeal
ganglion
---- prevertebral ganglia: celiac ganglia,
aorticorenal ganglia
superior mesenteric ganglia
inferior mesenteric ganglia
Marong Fang, PhD.
Institute of Anatomy & Cell Biology
The communicating branches:
--link the sympathetic ganglion with the corresponding spinal nerve.
-- 2 types: white and gray communicating branches
white communicating branches
sympathetic preganglionic fiberse
arise from the neurons of lateral horn from T1~L3
segments of spinal nerves.
about 15 pairs
via the anterior roots of corresponding spinal nerves to
communicate with the paravertebral ganglia.
gray communicating branches: peripheral blood vessels, sweat glands
& arrectores pilorum
sympathetic postganglionic fiberse
arise from the neurons of the paravertebral ganglia and
communicate with the 31 pairs of spinal nerves.
Marong Fang, PhD.
Institute of Anatomy & Cell Biology
Marong Fang, PhD.
Institute of Anatomy & Cell Biology
Once a preganglionic axon reaches the chain ganglion, it may:
…synapse with a
ganglionic neuron …
the same chain ganglion.
…ascend or
descend in the trunk
to synapse within
another chain
ganglion.
…pass through the chain ganglion and emerge
from the chain … splanchnic nerve.. synapsing.
Marong Fang, PhD.
Institute of Anatomy & Cell Biology
Marong Fang, PhD.
Institute of Anatomy & Cell Biology
Three fates of postganglionic fibers
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Back to a spinal nerve
along gray communicating
branches ( 31 pairs ) to
terminate in blood vessels,
arrectores pilorum and
sweat glands of head, neck,
trunk and limbs
The fibers from their
networks around blood
vessels passing to visceral
end organs
Terminate directly in certain
organs
Marong Fang, PhD.
Institute of Anatomy & Cell Biology
Distribution of sympathetic nerve
Preganglionic fibers Postganglionic fibers
T1~T5
Head, neck, upper limb
and thoracic viscera
T5~T12
Abdominal viscera
L1~L3
Pelvic viscera and lower
limb
Marong Fang, PhD.
Institute of Anatomy & Cell Biology
Parasympathetic part
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Lower center: located in four pairs parasympathetic
nuclei in brain stem and in sacral parasympathetic
nucleus of spinal cord segments S2~S4
Parasympathetic ganglia: terminal ganglia are
near or within the wall of a visceral organ
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Para-organ ganglia ：
 Ciliary ganglion
 Pterygopalatine ganglion
 Submandibular ganglion
 Otic ganglion
Intramural ganglia
Parasympathetic Division
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4 of 12 pairs of cranial nerves contain
preganglionic parasympathetic fibers.
Preganglionic fibers are long,
postganglionic fibers are short.
Vagus:

Innervate heart, lungs esophagus, stomach,
pancreas, liver, small intestine and upper half
of the large intestine.
Marong Fang, PhD.
Institute of Anatomy & Cell Biology
Parasympathetic Division
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Preganglionic fibers originate in midbrain,
medulla, and pons; and in the 2-4 sacral
levels of the spinal cord.
Preganglionic fibers synapse in ganglia
located next to or within organs innervated.
Do not travel within spinal nerves.

Do not innervate blood vessels, sweat
glands,and arrector pili muscles.
Marong Fang, PhD.
Institute of Anatomy & Cell Biology
Parasympathetic Effects
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Stimulation of separate parasympathetic
nerves.
Release ACh.
Relaxing effects:
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Decrease heart rate (HR).
Dilate blood vessels.
Increase GI activity.
Marong Fang, PhD.
Institute of Anatomy & Cell Biology
Cranial portion
Ⅲ
accessory oculomotor nucleus
〈○
sphincter pupillae and ciliary muscles
ciliary ganglion
Ⅶ
pterygopalatine ganglion
〈○
lacrimal gland
superior salivatory nucleus
〈○
submandibular ganglion
sublingual gland
submandibular gland
Ⅸ
〈○
otic ganglion
inferior salivator nucleus
Ⅹ
dorsal nucleus of vagus n.
〈○
terminal ganglia
parotid gland
heart, lungs, liver, spleen,
kidneys,alimentary tract
as far as left colic flexure
 E-W
nucleus----parasympathetic preganglionic fibers
(via oculomotor nerve)----ciliary ganglion (relay)---parasympathetic postganglionic fibers (short ciliary
nerves)---- supply the ciliary m. and sphincter pupillae
 superior salivatory nucleus----parasympathetic preganglionic
fibers(via the facial nerve )----greater petrosal nerve---pterygopalatine ganglion (relay)----parasympathetic
postganglionic fibers (via the maxillary—zygomatic – lacrimal
nerves)---- supply the lacrimal gland
Marong Fang, PhD.
Institute of Anatomy & Cell Biology
Marong Fang, PhD.
Institute of Anatomy & Cell Biology
Marong Fang, PhD.
Institute of Anatomy & Cell Biology
 superior salivatory nucleus----parasympathetic preganglionic
fibers (via facial n.– chorda tympani – lingual n.)---submandibular ganglion(relay)----parasympathetic
postganglionic fibers----supply the submandibular and
sublingual glands
Marong Fang, PhD.
Institute of Anatomy & Cell Biology
superior salivatory nucleus-
Facial n.
Marong Fang, PhD.
Institute of Anatomy & Cell Biology
Inferior salivatory nucleus----parasympathetic preganglionic
fibers (via glossopharyngeal n.– tympanic n. – lesser petrosal n.)
---- otic ganglion (relay) ---- parasympathetic postganglionic
fibers(via auriculotemporal n.) ---- supply parotid gland
Marong Fang, PhD.
Institute of Anatomy & Cell Biology
Marong Fang, PhD.
Institute of Anatomy & Cell Biology
 dorsal nucleus of vagus n. ---- parasympathetic preganglionic
fibers (via the vagus n. and it’s branches) ---- ganglia in organs
(relay) ---- parasympathetic postganglionic fibers ---- supply the
organs of neck, thorax and abdomen (above the left colic flexure).
Marong Fang, PhD.
Institute of Anatomy & Cell Biology
Marong Fang, PhD.
Institute of Anatomy & Cell Biology
Sacral portion
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Preganglionic fibers from sacral
parasympathetic nucleus leave
spinal cord with anterior roots
of the spinal nerves S2~S4,
Then leave sacral nerves and
form pelvic splanchnic nerve
and travel by way of pelvic
plexus to terminal ganglia in
pelvic cavity
Postganglionic fibers terminate
in descending and sigmoid
colon, rectum and pelvic
viscera
 The sacral portion of parasympathetic nervous system:
sacral parasympathetic nucleus ----parasympathetic
preganglionic fibers (via corresponding sacral nerves ---- 3
pelvic splanchnic nerves ---- pelvic plexus and it’s branches ) --ganglia in organs (relay) ---- supply the pelvic organs,
descending and sigmoid colons and rectum.
Marong Fang, PhD.
Institute of Anatomy & Cell Biology
Parasympathetic Division

Preganglionic fibers from the sacral
level innervate the lower half of large
intestine, the rectum, urinary and
reproductive systems.
Marong Fang, PhD.
Institute of Anatomy & Cell Biology
Main differences between sympathetic
and parasympathetic
Main differences between sympathetic and parasympathetic
Sympathetic
Parasympathetic
Lower center
Lateral gray horn of
spinal cord segments
T1~L3
Four pairs parasympathetic
nuclei and sacral
parasympathetic nucleus
Ganglia
Paravertebral,
prevertebral
Terminal
Preganglionic f.
Shorter
Longer
Postganglionic f.
Longer
Shorter
Pre: Postganglionic
1: many more
1: a few
Distributions
Throughout the body
Limited primarily to head
and viscera of thorax,
abdomen, and pelvis
Different action
Prepares for emergency
situation (fight or flight)
Conserve and restore body
energy (rest and relaxation)
Visceral plexuses
Cardiac plexuses
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Superficial , below aortic
arch
Deep, anterior to
bifurcation on trachea
Pulmonary plexus
Celiac plexus
Abdominal aortic plexus
Hypogastric plexus
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Superior hypogastric
plexus
Inferior hypogastric
plexus (pelvic plexus)
Visceral sensory nerves
Nucleus of solitary tract
Ⅶ，Ⅸ, Ⅹ
Thalamus
Enteroceptors
Posterior horn
Cerebral
cortex
Hypothalamus
Effectors
Sympathetic nerve
Pelvic splanchnic nerve
Somatic motor neurons
visceral motor neuclei
Visceral pain
BRAIN
1
Visceral sense is
conveyed by visceral
nerves
sensory fibres in
Marong Fang, PhD.
visceral nerves
Institute of Anatomy & Cell Biology
Referred pain (reflective pain) is a term
used to describe the phenomenon of pain
perceived at a site adjacent to or at a
distance from the site of an injury's origin.
One of the best examples of this is during
ischemia brought on by a heart attack
where pain is often felt in the neck,
shoulders, and back rather than in the
chest, the site of the injury.
Marong Fang, PhD.
Institute of Anatomy & Cell Biology

The cardiac general visceral sensory pain fibers
follow the sympathetics back to the spinal cord and
have their cell bodies located in thoracic dorsal root
ganglia.Also, the dermatomes of this region of the
body wall and upper limb have their neuronal cell
bodies in the same dorsal root ganglia . and
synapse in the same second order neurons in the
spinal cord segments (T1-5) as the general visceral
sensory fibers from the heart. The CNS does not
clearly discern whether the pain is coming from the
body wall or from the viscera
Marong Fang, PhD.
Institute of Anatomy & Cell Biology
Visceral pain
How is pain felt?
Case: A 50-yearold man with a
history of high
cholesterol
presents with
retrosternal pain,
which later radiates
to the chest, armpit
and shoulder on
the left.
1) Pain may be felt
from the affected
organ
2
BRAIN
T1 - T5
C3,4,5
HEART
PERICARDIUM
phrenic also to
pericardium, for
retrosternal pain
Marong Fang, PhD.
Institute of Anatomy & Cell Biology
Visceral pain
How is pain felt?
Case: A 50-yearold man with a
history of high
cholesterol
presents with
retrosternal pain,
which later radiates
to the chest, armpit
and shoulder on
the left.
2) Pain may be
'referred' to
nearby
dermatomes
3
BRAIN
T1 - T5
HEART
Marong Fang, PhD.
Institute of Anatomy & Cell Biology
CHEST
& ARM
Visceral pain
How is pain felt?
Case: A 50-yearold man with a
history of high
cholesterol
presents with
retrosternal pain,
which later radiates
to the chest, armpit
and shoulder on
the left.
3) Pain may be
'referred' to
distant
dermatomes
4
BRAIN
C3,
T1 -4,T5
5
HEART
PERICARDIUM
NECK and
SHOULDE
R
Marong Fang, PhD.
Institute of Anatomy & Cell Biology
Referred pain