5. Autonomic Nervous System
• Introduction
– Visceral component of
nervous system ,
function closely related
to somatic nervous
system
– Visceral afferent
pathways resemble
somatic afferent
– Peripheral processes –
auotonomic ganglia –
somatic nerves
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6. Visceral Afferents
-Cell bodies –unipolar –
present in cranial sensory or
dorsal root ganglia
-Central processes –with
somatic afferents into CNS
–establish connections
6
7. Visceral Efferent
• Visceral efferent
pathways in ANS differ
from their somatic
equivalents
• pre-ganglionic neurons:
– Somata are located in
• visceral efferent nuclei &
• in lateral grey columns
– axons are
• myelinated ,
• pass to peripheral ganglia
• synapse with
postganglionic neurons
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11. • Sympathetic –mass
response
- Constriction of cutaneous
arteries
- Cardiac acceleration
- Rise in blood pressure
- Contraction of sphincters
- Depression of peristalsis
• Sympathetic:
mobilization & increased
metabolism
“fight, flight or fright” or
“fight, flight or freeze”
11
12. Neurotransmitters:
• pre-ganglionic neurons of
both are cholinergic
• post-ganglionic
– parasympathetic –cholinergic
– sympathetic –nor-adrenergic
• principal co-transmitters
– ATP , Neuropeptide Y
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13. Sympathetic Nervous System
• Development :-
-During 5th week, neural crest
cells migrate along sides of
spinal cord ganglia -
dorsolateral to aorta
-Some neural crest cells
migrate ventral to aorta
pre-aortic ganglia – celiac
& mesenteric ganglia
13
14. • Other neural crest cells
migrate to heart, lungs, GIT
terminal ganglia
• Axons of sympathetic
neurones in
intermediolateral cell
column of thoracolumbar
seg of spinal cord
pass through ventral root of
spinal nerve & white ramus
communicans to reach
paravertebral ganglia
14
15. • Synapse with neurons –
ascend / descend in
sympathetic trunk
• Other presynaptic fibers –
pass through paravertebral
ganglia without synapsing –
splanchnic nerves to viscera
• Post synaptic fibres –grey
rami from sympathetic
ganglion into spinal nerve
• Sympathetic trunk –
ascending & descending
fibres
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16. Sympathetic Trunk
• Two ganglionated nerve
cords –either side of
vertebral column
• White & grey rami
communicantes
• Location –neck ,thorax,
abdomen, pelvis
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17. Preganglionic neurones:
• Cell bodies of preganglionic
sympathetic neurons –in
lateral horn
• Axons –myelinated ,diam
-1.5 - 4 microm
• Leave cord in ventral nerve
roots – pass into spinal
nerves, soon leave in white
rami communicants
17
18. Behaviour of Preganglionic Fibres
• Synapse with neurons in
nearest ganglion or may
ascend or descend
• Fibres terminate in single
ganglion or through
collateral branches –
synapse
• Fibres may ascend or
descend without synapsing
–emerge in branches of
sympathetic trunk –synapse
in ganglia of autonomic
plexus
18
19. Postganglionic Neurones of Sympathetic
Nervous System
• Somata of postganglionic
neurons –in ganglia of
sympathetic trunk
• Axons –unmyelinated,
return to spinal nerve
through grey ramus just
proximal to white ramus &
then form dorsal & ventral
ramus
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20. Cervical Sympathetic Trunk
• B/w Carotid sheath and
prevertebral muscles
• Internal carotid nerve
• Three cervical ganglia
– Superior
– Middle
– Inferior
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21. Superior Cervical Ganglion
• Largest ganglion
• Lies in front of transverse
processes of C2 and C3
vertebrae
• Branches
– Medial
– Lateral
21
22. Middle Cervical Ganglion
• Smallest of the Cervical
ganglion
• Lies on the C6
vertebra in front or behind
Inf. thyroid artery
• Branches
– grey rami communicantes
– Cardiac branch
– Vascular Branch
22
23. Stellate Ganglion
• Formed by the fusion of
C7,C8 andT1 ganglia
• Lies b/w neck of 1st Rib and
transverse process of C7
vertebra
• Branches
– Grey rami communicans
– Vascular branches
23
24. Sympathetic supply – Head and Neck
• Preganglionic fibres – T1-T5
segments of Spinal Cord
• Ascend in Sympathetic Trunk
• Synapse in cervical ganglia
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25. Thoracic Sympathetic Trunk
• Comprises of 11 ganglia
• Ganglia lie against the
heads of ribs
• Branches
– Grey rami
communicans
– Pul. And cardiac
Plexus
– Splanchnic Nerves
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26. Coeliac Plexus
• Situated around the origin
of coeliac artery
• Formed by greater
Splanchnic Nerves and Ist
lumbar sympathetic nerves
• Nerves from the plexus
supply abdominal viscera
via blood vessels
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27. Lumbar Sympathetic Trunk
• Lies retroperitoneally on
the anterolat. surface of
lumbar vertebrae
• Rt side – overlapped by IVC
• Lt side – overlapped by
Aorta
• Branches
– Splanchnic nerves
– Grey rami communicantes
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35. • Referred pain –diffuse
localization & radiation
• Zone of reference of pain
from int organ coincides
with part of body served
by somatic sensory
neurons assoc with same
segment of spinal cord
35
36. Referred Pain
• Heart –middle &
inferior cervical cardiac
nerves, thoracic cardiac
branches of left
sympathetic chain
• Gall bladder –greater
splanchnic nerve ,
diaphragm –phrenic
nerve
36