1. SYMPATHETIC NERVOUS SYSTEM
By DR QAZI IMTIAZ RASOOL
18-Sep-18

2. Sympathetic Nervous System
Describe the origin and the actions of sympathetic supply to different body regions: head and neck, thorax, abdomen, pelvis and body wall.
Relate the knowledge to clinical conditions resulting from sympathetic disorders (Horner’s syndrome).
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3. 1 . Anatomically/Morphological
A.N.S.
The autonomic nervous system can be divided and viewed 3 different ways:
1 . Anatomically/Morphological
Sym
Para
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4. 2. Chemically/Pharmacolgical
Chol
Adren
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5. Chemical Division of the A.N.S
The Cholinergic NS derives it’s name from the word acetylcholine
The Adrenergic NS derives it’s name form the word adrenalin
Epinephrine is an external form of the body-producing drug adrenalin.
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6. 3.Functional/physiological
excitatory inhibitory
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7. 6. “E” division SYMPATHETIC DIVISION 2.ADRENERGIC,NON-ADRENERGIC
1. THORACO-LUMBAR
2.ADRENERGIC,NON-ADRENERGIC
3.NERVOUS SYSTEM OF TODAY
4.CATABOLIC SYSTEM
5.ERGOTROPIC SYSTEM
6. “E” division
ERGO= WORK, HENCE ENERGY TROPIC =RELEASING, CANNON 1920 ,
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8. exercise,
excitement,
emergency,
embarrassment
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9. LIFE
POSSIBLE WITHOUT IT
SUBJECT IS SHELTERED AS THEY R LESS RESISTANT FOR EXTREME OF STRESS
SUBJECT IS
WEAK
APTHETIC
LOWER TEMP,
LOW BP
LIF3E IS POSSIBLE WITHOUT THIS IVISION BUT THE SUBJECT IS SHELTERED AS THEY R LESS RESISTANT FOR EXTREME OF STRESS +INTERNAL ENVIORMENT CHANGES
SUBJECT IS WEAK APTHETIC= LOSS OF EMOTIONS , LOWER TEMP, LOW BP
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10. Sympathetic Pathways
Axons leave the sympathetic trunk in 5 possible ways:
spinal nerves
Perivascular plexus i.e along blood vessel, e.g. internal carotid artery.
3. sympathetic nerves straight to the target organ.e.g.e heart.
4. splanchnic nerves
5. Adrenal Medulla Pathway
Travel along the spinal nerves.
2.Travel along the blood vessel, e.g. internal carotid artery.
3.Travel straight to the target organ.e.g. fibers to the heart.
Perivascular plexus
- Sympathetic : postganglionic
sympathetic fibers AS SYM; NERVES—VISERAL ORGANS, SPINAL NERVE PARTS GO TO VISERAL EFFECTOR PARTS
-Parasympathetic : preganglionic
parasympathetic fibers
- Sensory fibers
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11. Organs of supply Cutaneous blood vessels Deep blood vessels Glands
cardiac muscles
pilomotor
Smooth muscles
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12. Physiological Anatomy
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13. Preganglionic fibers Cell-bodies inter­mediolateral horn
Preganglionic neurons originate in thoracic + lumbar levels of the spinal cord (T1-L2).
inter­mediolateral horn
5000 cell bodies
(lamina VII)
Tracts Desend From Above
5000 cell bodies in lateral horn INTERMEDIOLATERAL HORN, C 8,T1 to L2. fibers which comprise the sympathetic system originate in the inter­mediolateral horn (lamina VII)
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14. Preganglionic axons → anterior root of a spinal nerve → white ramus → sympathetic trunk ganglion.
White rami communicantes: structures containing sympathetic preganglionic axons that connect the anterior ramus of the spinal nerve with the ganglia of the sympathetic trunk.
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15. 5 types of sympathetic ganglia
Paravertebral
Prevertebral/colletral
Terminal
Intermediate
Adrenal gland
Contains more ganglia than the parasympathetic division AUTONOMIC GANGLIA Sympathetic trunk; Walls visceral organs
Cell shape:
Multipolar (stellate)
Bipolar; Unipolar  very few
Cell size: smaller (15 – 45 μ) than C-S series
Cell structure:
Soma typical
Several processes pierce capsule
Short dendrites may form glomerulus
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16. sympathetic ganglion 20000–30000 nerve cell bodies
more ganglia than PNS division
Multipolar (stellate) Bipolar; Unipolar  very few
Short dendrites may form glomerulus
Satellate cells– maintain the neural enviorment
R motor ganglia
from which neuroblastoma tumours arise
They contain approximately 20000–30000 nerve cell bodies and are located close to and on either side of the spinal cord in long chains. Sympathetic ganglia are the tissue from which neuroblastoma tumours arise The sympathetic ganglia lie close to the vertebral bodies and are also known as paravertebral ganglia. They are strung together to form a sympathetic or paravertebral chain. There are two of these chains, one on either side of the vertebral column connected in front of the coccyx by the single ganglion impar
Some of the fibers from nerve cells within the ganglia return to the spinal nerve trunk via a gray ramus. The fibers traveling through the white rami are myelinated while those in the gray rami are not, and this fact is responsible for their respective names. Each of the twelve thoracic and first two lumbar nerves is in contact with a paravertebral ganglion via a white and gray ramus. However, there are three ganglia in the chain above the thoracic region as well as several below L2 (Fig. 14-2). Each of these additional ganglia is connected to a spinal nerve by a single gray ramus
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17. PARAVERTEBRAL-SYM CHAIN
The ganglia vary in size, position, and number, but there are typically 23 (+- 1)ganglia in each sympathetic chain…
3 cervical
11 thoracic
4 lumbar
4 sacral
1 coccygeal (ganglion impar)
Remember that autonomic ganglion are motor ganglia, containing the cell bodies of motor neurons , underlying the pleural, peritoneum
Lie in thorax ,abdomen, pelvis – along the arteries
They are sites of synapse and information transmission from pre to postganglionic neurons. Paravertebral ganglion : Locate beside the vertebral column (In sympathetic chain)
Superior Cervical Ganglion (SCG) million cells
- Cervical ganglion pair Middle Cervical Ganglion (MCG)
Inferior Cervical Ganglion (ICG) Stellate ganglion (ICG + T1 ganglion)
- Thoracic ganglion 12 pair
- Lumbar ganglion 4 (5) pair
- Sacral ganglion 4 (5) pair
- Coccygeal ganglion 1 ganglion (single) called ganglion impar
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19. Sympathetic trunk ganglia: 3 cervical, 11 or 12 thoracic, 4 or 5 lumbar, 4 or 5 sacral and 1 coccygeal.
Postganglionic neurons from the
superior cervical region-head and heart.
middle cervical ganglion and the inferior cervical ganglion-heart.
Thoracic sympathetic trunk- heart, lungs, and bronchi.
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20. Postganglionic Fibers
Spinal nerves
1. Gray rami communicantes: postganglionic neurons leave sympathetic trunk by entering a short pathway called a gray rami communicantes & merge with
anterior ramus of a spinal nerve.
2. Each spinal nerve carries a grey rami from its corresponding ganglias,
3. 8% in spinal nerve r sym; .
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21. superior cervical ganglia
Close to base skull, Trans; proc; of C2-3,
Behind carotid sheath
Fusion of smaller individual cervical ganglia
Largest , Contain Pre, Post, Inter-neurones,
satellate cells.
4. Pathways to head (T1-T4) ascend to S.C.G.
Postganglionic neurons enter ventral rami via gray rami communicantes and then travel to effectors.
Rami communicantes are associated only with the sympathetic division
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22. Superior Cervical Ganglion
1million cells
1: 190
Post gang; enter ventral ramus via gray- rami communicantes and then travel to effectors.
C1-4, head and neck
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23. Pathways to head Serve skin and blood vessels of the head
Stimulate the dilator iris muscles of eye
Inhibit nasal and salivary glands
Innervate the smooth (tarsal) muscle that lifts the upper eyelid
Sends direct branches as superior Cardiac Nerve to heart, skin.
The superior, middle, and inferior cervical ganglia probably represent the fusion of smaller individual cervical ganglia. These three send gray rami to all eight cervical spinal nerves. The superior cervical ganglion sends to the first four cervical nerves,. Similarly, a variable number of ganglia (four to eight) below L2 send gray rami to all of the spinal nerves below this level. Consequently, all 31 pairs of spinal nerves are in contact with the sympathetic chain and carry fibers of the sympathetic system. This is an important feature, enabling those effector organs which are innervated only by spinal nerves (cutaneous and skeletal muscle blood vessels, sweat glands, and pilomotor smooth muscle) to receive sympathetic input.
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24. Middle Cervical Ganglion (MCG)
Lies On Vert; C6
Smallest
Pathways To (T1-T6) Ascend To M.C.G.
Post; Thyroid,para
Middle Cardiac Nerve, skin
Gray Rami C5-6
the smaller middle cervical ganglion
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25. Inferior Cervical /STELLATE Ganglion
Large
Between Neck Of Ist Rib and Trans; Proc; Of C7
Lies Behind Vertrebral Artery
Supplies The Next Two, C7-8
Inferior Cardiac Nerve, skin
Also Along Subclavian Artery
SNS efferents to the myocardium funnel through the paired stellate ganglion. Right stellate stimulation decreases systolic duration and increases the heart rate. Left stellate ganglion stimulation increases mean arterial pressure & left ventricular contractility without causing a substantial change in the heart rate.
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26. GANGLIA – GENERAL FEATURES Supported/Surrounded by C.T.
Nerve fibers Of ganglionic neurons Synapse with ganglionic neurons Pass through – no synapses
Size: small to large masses – up to 50,000 neurons
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29. 5.Adrenal gland 2. Structurally and functionally, they are2 glands:
Adrenal=a modified sym: gang:
pyramid-shaped , on top of each kidney
2. Structurally and functionally, they are2 glands:
Adrenal cortex (outside) glandular (epithelial) tissue
Adrenal medulla (inside) is nervous hormonal tissue.
3. Embryologically derived from pheochromoblasts
differentiate into modified neuronal cells
Pheochromocytes (= chromaffin cells; axonless secretory cells
4. Acts as a peripheral amplifier
Adrenal glands (toward kidney) pyramid-shaped glands on top of each kidney
Structurally and functionally, they are two glands: Adrenal medulla (inside) nervous tissue that is the hormonal branch of the sympathetic nervous system (fight/flight)
Adrenal cortex (outside) glandular (epithelial) tissue
embryologically derived from pheochromoblasts differentiate into modified neuronal cells
an extension of the sympathetic nervous system acts as a peripheral amplifier activated by same stimuli as the sympathetic nervous system more gland than nerve chromaffin cells
acts like sympathetic ganglion
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30. Sympathetic Variosities are long 1:25,000 effector cells; cleft ∼50 nm across
Synapses of the ANS are specialized for their function. Rather than possessing synaptic terminals that are typical of somatic motor axons, many postganglionic autonomic neurons have bulbous expansions, or varicosities, that are distributed along their axons within their target organ It was once believed that these varicosities indicated that neurotransmitter release sites of the ANS did not form close contact with end organs and that neurotransmitters needed to diffuse long distances across the extracellular space to reach their targets. However, we now recognize that many varicosities form synapses with their targets, with a synaptic cleft extending ∼50 nm across. At each varicosity, autonomic axons form an "en passant" synapse with their end-organ target. This arrangement results in an increase in the number of targets that a single axonal branch can influence, with wider distribution of autonomic output
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31. Diagram showing pathways from (1) the hypothalamus to the intermediolateral column in the spinal cord (first-order neuron). (2) A preganglionic sympathetic neuron with the cell body in the intermediolateral column gets a synapse from (1) and sends an axon to the superior cervical ganglion. (3) A postganglionic sympathetic neuron with the cell body in the superior cervical ganglion sends axons to pupillary dilator (smooth) muscles.
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32. Horner’s Syndrome in descending pathway b/w T1-T5 Damage to SCG.
1. Miosis – lack of SNS innervation of dilator pupillae
( nothing to counteract PNS sphincter pupillae)
2. Ptosis – drooping of upper eyelid ( inactivity of superior
tarsal muscle (smooth muscle)
3. Anhidrosis – lack of facial sweating
if lesion occurs before branching of sympathetics in the periphery
4. Enophthalmos – sinking of one eye w/in the orbit
(possibly due to inactivity of smooth muscle)
Horner’s Syndrome: results from loss of the normal sympathetic innervation on one side of the face. The D/D of this syndrome is large, but it can be narrowed if the site of involvement of the sympathetic pathways can be identified.
Lesion of SNS in descending pathway b/w T1-T5 Damage to superior cervical ganglia
 Signs/Symptoms of Horner’s
Miosis – constriction of pupil due to lack of SNS innervation of dilator pupillae
Pupil constricts b/c there is nothing to counteract PSNS-controlled sphincter pupillae muscles
Ptosis – drooping of upper eyelid due to inactivity of SNS innervation of superior tarsal muscle (smooth muscle)
Also seen in Myasthenia Gravis (ie you would have ptosis, but NO miosis)
Could also occur b/c of lesion to CN III – GSE component
But would get more pronounced eyelid drop
Anhidrosis – lack of facial sweating
It would be apparent if lesion occurs before branching of sympathetics in the periphery
Branch to facial sweat glands follows ECA
Branch to eye follows ICA
Enophthalmos – sinking of one eye w/in the orbit (possibly due to inactivity of smooth muscle)
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