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Autonomic nervous systemSympathetic nervous systemSympathetic nervous system

Dr

Swati Patil

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• Autonomic nervous system -History -Introduction -Types :- Sympathetic –Development -Introduction -Course -Types -Applied

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Autonomic Nervous System• Self regulating• History:– 1898 - J.N.Langley assigned the term Autonomic

Nervous System

– 1921 – subdivided ANS into• Sympathetic• Parasympathetic• Enteric

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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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Visceral Afferents

-Cell bodies –unipolar –present in cranial sensory or dorsal root ganglia

-Central processes –with somatic afferents into CNS –establish connections

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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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Visceral Efferents

Pre-ganglionic

ganglion

Post-ganglionic

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• Post-ganglionic neurons –axons are unmyelinated , more numerous

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Subdivisions of ANS

• Sympathetic• Parasympathetic• Enteric

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• 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”

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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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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

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• 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

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• 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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Sympathetic Trunk

• Two ganglionated nerve cords –either side of vertebral column

• White & grey rami communicantes

• Location –neck ,thorax, abdomen, pelvis

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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

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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

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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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Cervical Sympathetic Trunk

• B/w Carotid sheath and prevertebral muscles

• Internal carotid nerve• Three cervical ganglia

– Superior– Middle– Inferior

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Superior Cervical Ganglion

• Largest ganglion• Lies in front of transverse

processes of C2 and C3 vertebrae

• Branches– Medial– Lateral

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Middle Cervical Ganglion

• Smallest of the Cervical ganglion

• Lies on the C6vertebra in front or behind Inf. thyroid artery

• Branches– grey rami communicantes– Cardiac branch– Vascular Branch

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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

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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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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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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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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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Hypogastric Plexuses• Superior hypogastric plexus:- -location -formation -branches

• Inferior hypogastric plexus :- -location -formation -branches

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Adrenal Medulla

• Neural crest cells –secretary cells of medulla

• Sympathetic supply –preganglionic sympathetic neurons

• Secretary cells –postganglionic sympathetic neurons –lack axons or dendrites

• Larger secretory cells –secrete adrenaline & NA

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Summary

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Sympathetic Ganglion

Histology :• Connective tissue,

ganglion, capsule cells• Nerve cells –multipolar,

smaller• Nucleolus –prominent

eccentric

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Sympathetic Ganglion

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Enteric Nervous System

• Myenteric (Auerbach’s) plexus & submucosal (Meissner) plexus

• Plexus –small enteric ganglia –joined by thin nerves –unmyelinated

• Avascular –nutrition by diffusion

• Neurones –excitatory & inhibitory

• Afferents to ENS -2 types –cholinergic & NA

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Pain Afferents• Sensory neurones –pain

in thoracic & abdominal organs

• Cell bodies –dorsal root ganglia

• Peripheral processes –white communicating rami –sympathetic trunk –viscera

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• 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

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Referred Pain

• Heart –middle & inferior cervical cardiac nerves, thoracic cardiac branches of left sympathetic chain

• Gall bladder –greater splanchnic nerve , diaphragm –phrenic nerve

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• Stomach –epigastrium –Rt & Lt greater splanchnic nerves

• Duodenal ulcer –AAW –T9 T10

• Appendix –lesser splanchnic nerves –T10

• Pelvis & ureter –least splanchnic nerves –loin & groin

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Surgical Sympathectomy

• Indications– Peripheral vascular disease –sympathectomy –temporary

vasodilatation –development of collaterals

– Hyperhidrosis –sympathectomy –permanent relief

– Relief of Pain –a) visceral pain –excision / destruction –coeliac ganglia –Ca pancreas, chronic pancreatits

– b) causlgia –intense pain

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Upper Thoracic and Cervical Sympathectomy

• Upper limb -2 & 3 thoracic ganglia with rami & intervening part

• 1st thoracic –not removed, preganglionic fibres not arise above T2 (removal –Horner’s syndrome)

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Kuntz Nerve

• Communicating branch B/w T1and T2 nerves

• Receives Grey rami from Stellate and T2 ganglia

• Clinical relevance –failure to identify during thoracic sympathectomy

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Lumbar Sympathectomy

• Gangliectomy -3 & 4 lumbar ganglia & intervening trunk

• Removal of LI is harmful – interferes with ejaculation

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Horner’s Syndrome

• Preganglionic –white ramus of T1 –sympathetic trunk –superior cervical ganglion –postganglionic fibres (ICA) –ophthalmic –nasociliary –long ciliary branches

• Damage –vascular lesions of cortex / brainstem, cervical rib, Ca lung, thyroid, oesophagus

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Clinical features of Horner’s syndrome:

• Miosis –failure dilation –unopposed parasympathetic activity

• Partial ptosis –paralysis of LPS

• Anhydrosis –lesion of superior cervical ganglion

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Central Control of Sympathetic Nervous System

• Hypothalamus –controlling &integrating center

• Hypothalamus –autonomic nuclei –spinal cord –reticular formation

• Posterior & lateral nuclei –noradrenergic response

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