autonomic nervous system.ppt

8/13/2019 AUTONOMIC NERVOUS SYSTEM.ppt

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AUTONOMIC

NERVOUS SYSTEM



AUTONOMIC NERVOUS SYTEM

Motor part of the somatic motor system isconcerned with the innervation of the skeletalmuscle.

Cell bodies are either in the motor nucleus ofcranial nerves or anterior horn cells of spinalcord.

The motor part of the autonomic nervoussystem is concerned with the innervation ofcardiac and smooth muscles and glands.



The differences between somatic and autonomic

system is the pathway between cells in CNS and

target organ is interrupted by synapses in

ganglions called pre ganglions and post

ganglions.

The pre ganglionic cell bodies are always in the

CNS.

If sympathetic they are always in the lateral horn

cells of the thoracic and upper two lumbar

segments- Thoraco lumbar outflow.

If parasympathetic they are in certain cranial

nerves nuclei and in lateral horn cells of saccral

segments – cranio sacral outflow.



The post ganglionic ganglia in sympathetic either

in sympathetic ganglia or in autonomic plexus

situated in abdomen and pelvis. In parasympathetic it is present in the walls of

viscera or in the head and neck- four ganglia – a

distance from the structures concerned.



SYMPATHETIC NERVOUS

SYSTEM

Having reached the sympathetic ganglion, the

incoming preganglionic fibres may

1. Synapse with the cell bodies in a trunk ganglion they

enter or may run up or down to some other ganglion.2. May leave the trunk ganglion without synapse – pass

to an autonomic ganglion without synapse.

3. Only a small number of fibres leave the trunk withoutsynapse to pass to suprarenal gland where certain cells

can be regarded as modified ganglion cells.



Since there is no sympathetic outflow from thecervical nor lower lumbar and sacral parts ,

those preganglionic fibres which are destined tosynapse with cell bodies whose fibres are goingto run with cervical nerves ascend in thesympathetic trunk to cervical ganglion and those

for the lower lumbar and sacral nerves mustdescend in the trunk to lower lumbar and sacralganglia.

The sympathetic trunk extends alongside the vertebral column from the base of the skull tothe coccyx usually a ganglion for the spinalnerve.



Fusion occurs especially in the cervical region .

The upper four fuse to form the superior

cervical ganglion.

Fifth and sixth form middle cervical ganglion.

Seventh and eighth fuse as inferior cervical

ganglion (often with first thoracic to form

cervicothoracic or stellate ganglion).

Fibres from the lateral horn cells of each

segment leaves in the anterior nerve root (with

axons in the anterior horn cells) to reach spinal

nerve and its anterior ramus.



Connecting links from here to sympathetic trunkand its ganglion are rami communicantes – two innumber.

White ramus contains preganglionic fibres whichare myelinated hence called white.

Grey ramus contains efferent post ganglionic fibres

which are unmyelinated hence hrey.

Fibres of grey rami are distributed via branches ofspinal nerves to blood vessels, sweat glands and

erector pili muscles i.e. they are vasomotor,sudomotor and pilomotor.

All thoracic and upper two lumbar nerves haveboth white and grey rami connecting them tosympathetic ganglion.



But cervical and lower lumbar and sacral do not

have white rami.

Each sympathetic trunk ganglion has a collateral or visceral branch.

In addition to visceral branches all trunk ganlglia

give off vascular branches to adjacent large blood

vessels.

The cervical ganglia gives off branches to carotid

and vertebral arteries ( from superior cervical

ganglion ) including internal carotid nerve which

runs upwards on the artery of that name to form

internal carotid plexus as it enters the skull.



The afferent sympathetic fibres may hitch hike

along sympathetic efferent pathways all have cell

bodies in the posterior root ganglion of spinalnerves and not in sympathetic ganglia.

The afferent reach the spinal nerve via white

ramus then join the posterior root ganglion thecentral process enter the cord by the posterior

nerve root ( like any other afferent fibres).



PARASYMPATHETIC NERVOUS

SYSTEM

The distribution of parasympathetic fibres is

wholly visceral and not to trunk or limbs.

However suprarenal glands and gonads appear

to have only sympathetic supply.

The preganglionic fibres of cranial origin have

their cell bodies in the acessory ( Edinger

westphal) occulomotor nucleus, superior andinferior salivary nuclei of seventh and ninth

cranial nerves and dorsal motor nucleus of

vagus.



The preganglionic fibres for the first three are inthe four parasympathetic ganglia, vagal fibressynapse with post ganglionic cell bodies in the walls of the viscera supplied i.e. heart, lungs andgut.

The pregnglionic fibres of sacral origin arise

from cells in the grey horn of sacral segments 2-4 of spinal cord and constitute spinal cord andconstitute pelvic ‘splanchnic nerve’.

From inferior hypogastric pkexuses synapsearound post ganglionic cell bodies in the wallsof the viscera.



CERVICAL PARASYMPATHETIC

GANGLIA

They are four in number – ciliary,pterygopalatine, submandibular and otic ganglia.

Each has a parasympathetic, sympathetic and

sensory roots and branches of distribution. Parasympathetic root caries the preganglionic

fibres from cells of origin in the brainstem

nucleus- essential functional root – its fibressynapse whereas fibres of other roots simplypass through the ganglion.



Sympathetic root contains post ganglionic fibres

from the superior cervical gnaglion, whose

preganglionic cell bodies are in the lateral greyhorn of cord segments T1-3.

The sensory root contains the peripheral

processes of cell bodies in the trigeminalganglion.

The branches of each ganglion carry the post

ganglionic parasympathetc fibres to theparticular structures, requiring this kind of

localized motor innervation.



CILIARY GANGLION

PARASYMPATHETIC ROOT: From edinger westphal nucleus part of occulomotor nerve by abranch from nerve to inferior oblique muscle,

from inferior occulomotor nerve. SYMPATHETIC ROOT: From the superior

cervical ganglion by branches of internal carotidnerve.

SENSORY ROOT: From branches ofnasociliary nerve with cell bodies in trigeminalganglion.

BRANCHES: Short ciliary nervus to the eye.



PTERYGOPALATINE

GANGLION

PARASYMPATHETIC ROOT: From superior salivarynucleus by the nerve of pterygoid canal and fromgreater petrosal nerve from nervus intermedius part ofthe facial nerve.

SYMPATHETIC ROOT: From superior cervicalganglion by the internal carotid nerve, deep petrosalnerve and the nerve of pterygoid canal.

SENSORY ROOT: From a branch of maxillary nerve with cell bodies in trigeminal ganglion.

BRANCHES: To lacrimal gland via zygomatic andlacrimal nerves and to mucous glands in the nose,nasopharynx and palate via maxillary nerve branches. Afew fibres are taste fibres from palate running in greater

petrosal nervewith cell bodies in geniculate ganglion offacial nerve.



SUBMANDIBULAR GANGLION

PARASYMPATHETIC ROOT: From superior

salivatory nucleus by the nervus intermedius part of

facial nerve and chorda tympani joining the lingual

nerve.

SYMPATHETIC ROOT: From the superior cervical

ganglion by fibres running with the facial nerve.

SENSORY ROOT: From a bracnch of the lingualnerve with the cell bodies in trigeminal ganglion.

BRANCHES: To submandibular and sub-lingual glands

via branches of lingual nerve.



OTIC GANGLION

PARASYMPATHETIC ROOT: From theinferior salivary nucleus by the glossopharyngealnerve and its tympanic branch to the tympanicplexus and then to the lesser petrosal nerve.

SYMPATHETIC ROOT: From the superiorcervical ganglion by fibres running with middlemeningeal artery.

SENSORY ROOT: From the auriculotemporalnerve with the cell bodies in the trigeminalganglion.

BRANCHES: To the parotid gland via filaments

of the auriculotemporal nerve.



OTIC GANGLION

Unlike the other ganglia, the otic ganglion has an

additional somatic motor root, from the nerve

to the medial pterygoid; the fibres pass through

(without relay) to supply tensor tympani andtensor palati muscles.

autonomic nervous system.ppt

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