AUTONOMIC NERVOUS SYSTEM
INDIAN DENTAL ACADEMYLeader in continuing Dental Education
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NERVOUS SYSTEM
CONTROLES THE RAPID ACTIVITIES OF THE BODY
MUSCLE CONTRACTIONS VISCERAL EVENTS RATE OF SECRETION OF ENDOCRINE
GLANDS
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DEVELOPEMENT
IT BEGINS IN THE 3rd OF IU LIFE BY THE THICKENING OF THE ECTODERM
CALLED THE NEURAL PLATE WHICH FORMS THE NEURAL TUBE.
THE NEURAL CREST IS A MASS OF TISSUE BETWEEN THE NEURAL TUBE AND ECTODERM
BECOMES DIFFERNTIATED EVENTUALLY FORMS THE SPINAL NERVES AND CRANIAL NERVES.
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NERVOUS SYSTEM IS SUB-DIVIDED INTO 1) CENTRAL NERVOUS SYSTEM 2) PERIPHERAL NERVOUS SYSTEM
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CNS
COMPOSED OF 1) BRAIN 2) SPINAL CORD ( SPINAL MEDULLA)
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PNS
IT IS COMPOSED OF 1) CRANIAL 2) SPINAL NERVES 3) AND THEIR ASSOCIATED GANGLIA
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THE CENTRAL AND PERIPHERAL PARTS HAVE
1) SOMATIC 2) AUTONOMIC COMPONENTS
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SOMATIC
IT IS CONCERNED WITH 1) INNERVATION OF SKELETAL MUSCLE 2) TRANSMISSION OF SENSORY
INFORMATION
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AUTONOMIC
CONTROLTHE INTERNAL ENVIRONMENT OF THE BODY
CARDIAC MUSCLE SMOOTH MUSCLE GLANDS
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FUNTIONALY THERE IS ONLY ONE NERVOUS SYSTEM ALTHOUGH ANATOMICALY IT IS DESCRIBED AS A SEPARATE ENTITY
THE NERVOUS SYSTEM IS BAISICLY A SIMPLE PLAN – WITH
1) AFFERNT ( SENSORY) 2) EFFERENT ( MOTOR) PATHWAYS WITH INTERACTIONS WHICH ARE COMPLEX IN
CNS
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AUTONOMIC NERVOUS SYSTEM
CONTROLES VISCERAL FUNCTIONS OF THE BODY
CONTROLS THE ARTERIAL PRESSURE, GASTRO-INTESTINAL MOBILITY AND SECRETION .
URINARY BLADDER EMPTYING,SWEATING,BODY TEMPERATURE.
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CHARECTERISTICS
RAISE HEART RATE TO TWICE WITHIN 3-5 SECONDS.
WITHIN 10-15 SECONDS ARTERIAL PRESSURE DOUBLED.
SWEATING MAY BEGIN AND BLADDER MAY EMPTY INVOLUNTRILY WITHIN SECONDS
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IT IS THEESE RAPID CHANGES THAT ARE MEASURED BY LIE DETECTOR POLYGRAPH , REFLETING INNERMOST FEELINGS OF A PERSON.
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ANS is control centers located mainly in BRAIN STEM, SPINAL CORD,AND HYPOTHALAMUS .
THE AUTONOMIC NERVOUS SYSTEM ALSO OFTEN OPERATES BY MEANS OF VISCERAL REFLEXES
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THE EFFERENT AUTONOMIC SIGNALS ARE TRANAMITED TO THE BODY THROUGH TWO MAJOR SUB-DIVISIONS CALLED THE PARASYPATHETIC NERVOUS SYSTEM AND THE SYMPATHETIC NERVOUS SYSTEM.
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STRUCTURE OF ANS
IT CONSISTS OF PREGANGLIONIC NEURONS,
Pre ganglionic FIBRES POSTGANGLIONIC NEURONS, Post ganglionic FIBRES.
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Sympathetic nervous system helps in tackling of stress and emergency.
Parasympathetic nervous system helps in assimilation of food and conservation of energy
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SYMPATHETIC NERVOUS SYSTEM
PARA-VERTEBRAL GANGLIA THAT LIE TO THE TWO SIDES OF VERTEBRAL COLUMN.
PRE-VERTEBRAL GANGLIA (CELIAC AND HYPO-GASTRIC), AND NERVES EXTENDING FROM THE GANGLIA TO THE DIFFERENT INTERNAL ORGANS.
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Sympathetic
THE SYMPATHETIC NERVES ORIGINATES FROM THE SPINAL CORD BETWEEN THE SEGMENTS T-1 AND L-2 AND PASS FROM HERE FIRST INTO THE SYMPATHETIC CHAIN AND THEN TO THE TISSUES AND ORGANS THAT ARE STIMULATED BY SYMPATHETIC NERVES
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TYPICALLY THERE ARE 22 GANGLIA IN EACH CHAIN
CERVICAL = 3 THORASIC = 11 LUMBAR = 4 SACRAL = 4
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THE CERVICAL PORTION 0F EACH SYMPATHETIC TRUNK IS LOCATED IN THE NECK ANTERIOR TO THE PRE – VERTEBRAL MUSCLE .
IT IS SUB-DIVIDED INTO 1) SUP CERV GANGLION 2)MIDDLE CERV GANGLION 3)INF CERV GANGLION
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THE SUPERIOR CERVICAL GANGLIA IS POSTERIOR TO ICA AND ANTERIOR TO THE TRANSVERSE PROCESS OF SECOND CERVICAL VERTEBRAE
POST GANGLIONIC FIBERS SENT TO SWEAT GLANDS , SMOOTH MUSCLES OF THE EYE . BLOOD VESSELS OF FACE , NASAL MUCOSA, SALAIVARY GLANDS
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THE MIDDLE CERVICAL GANGLION IS SITUATED NEAR SIXTH CERVICAL VERTEBRAE AT THE LEVEL OF CRICOID CARTILLAGE
POST GANGLIONIC FIBERS SUPPLY THE HEART
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INFERIOR CERVICAL GANGLION IS LOCATED NEAR THE FIRST RIB .
ANTERIOR TO THE TRANSVERSE PROCESS OF 7TH CERVICAL VERTEBRAE
IT ALSO SUPPLY HEART. It is also known as stellate ganglion
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Thoracic portion
Consists of 11 segmentaly arranged ganglia Supplying to heart, lungs ,bronchi , thoracic
viscera.
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Lumbar portion
They are found on each side of corresponding lumbar vertebrae
They are four in number
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SOME PRE-GANGLIONIC FIBERS PASS THROUGH SYMPATHETIC TRUNK WITHOUT TERMINATING IN THE TRUNK BEYOND THE TRUNK THEY FORM NERVES KNOWN AS SPLANCHINIK NERVES .
AFTER PASSING THROUGH THE TRUNK OF GANGLIA , THE SPLANCHNIK NERVES FROM THORASIC AREA TERMINATE IN CELIAC GANGLION OR SOLAR PLEXUS
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PARASYMPATHETIC NERVOUS SYSTEM
THE PARASYMPATHETIC nervous system consists of fibers that leave through cranial nerves 3,7,9,10.
The second and third sacral spinal nerves Occasionally the 1 and 4 sacral nerves 75% of all the parasympathetic nerves are in
the vagus nerve
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The vagus nerve give parasympathetic fibers to the lungs esophagus stomach, small intestine , colons, liver, gallbladder, pancreas
Fibers of the 3rd nerve flow to puppillary sphincters and Ciliary muscles of the eye
7th nerve passes to the lacrimal nasal and sub mandibular gland.
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9th nerve give fibers to the parotid gland. Sacharal parasympathetic fibers congregate
in the pelvic nerves supplies colon rectum bladder.
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Characteristics
Sympathetic and parasympathetic nerve fibers secrete one or the other of two synaptic substances. Acetylcholine and nor epinephrine.
Those that secrete acetyl choline are cholinergic.
Those that secrete nor epinephrine is Adregenic.
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Preganglionic neurons are cholinergic in both systems
Almost all post ganglionic neurons of the parasympathetic system are also cholinergic.
Most of the post ganglionic sympathetic neurons are Adregenic.
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The terminal nerve endings of the parasympathetic system all or virtually all secrete acetylcholine and most of sympathetic nerve endings secrete nor-epinephrine.
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Acetylcholine receptors
Musacrnic Nicotinic
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Muscarnic
A poison from toad stools , activates only the muscarnic receptors and not the nicotinic receptors .
Atropine blocks it. Acetylcholine activates both of them . The muscarnic receptors are found in all effecter
cells stimulated by post ganglionic neurons of parasympathetic system.
Post ganglionic cholinergic neurons of sympathetic system
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M-1 ; NEURONAL RECEPTOR ; MAJOR ROLE IN MEDIATING GASTRIC SECRETION AND RELAXING LOWER ESOPHAGEAL SPHINCHTER.
M-2 ; cardiac receptors – predominantly mediate vagal bradycardia
M-3 ; visceral smooth muscle contraction and glandular secretions
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Nicotinic
Synapses between preganglionic and post ganglionic neurons of both sympathetic and parasympathetic systems
Present in the membranes of skeletal muscle fibers at the neuromuscular junction.
Selectively activated by nicotine and blocked by tubocurarine and hexamethonium
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N-m Present at skeletal muscle template . They mediate skeletal muscle contraction .
N-n present on ganglionic cells, adrenal medullary cells , spinal cord and in certain areas of brain
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Cholinergic system is anabolic Noradregenic system is catabolic
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Adregenic transmission
Restricted to sympathetic division of ANS Nor – adrenaline: acts as a transmitter at
postganglionic sympathetic sites Adrenaline ; role in brains Dopamine ; transmitter in basal ganglia,
limbic system.
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Alpha receptors
Alpha-1 : Located postjunctional on affecter neurons Contracts smooth muscle Vasoconstriction Gland- secretion Selective agonist –phenylephrine Selective antagonist -prazosin
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Alpha 2
Post junctional on nerve endings, also in brain & extra junctional in certain blood vessels
Functions vasoconstriction decreased insulin release platelet aggregation
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Selective agonist clonidine
Selective antagonist Yohimibine
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beta receptors
Beta 1 Located in heart, JG cells of the kidney Selective agonist is Dobutamine Selective antagonist is Metoprolol and Atenolol
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beta 2 receptors
Present In bronchi, blood vessels, urinary tract and eye
Selective agonist is Salbutomol Selective antagonist is Proponolol
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beta 3
Present in adipose tissue Potency of Nor adrenaline as agonist is
strong.
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Effects of stimulation on various organs
Sympathetic stimulation causes excitatory effects on certain organs but inhibitory on others
Likewise parasympathetic also.
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Eyes
Pupillary opening and focusing of the lens Sympathetic stimulation contracts the MERIDONIAL
FIBERS OF THE IRIS THAT DIALATE PUPIL. The parasympathetic stimulation contracts the
circular muscle to constrict the pupil . Parasympathetic constrict the pupil when excess
light enters it . Sympathetic are stimulated when during excitement – the pupil dilates
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Focusing of lens is controlled entirely by parasympathetic nervous system.
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Glands of the body
Nasal , lacrimal , salivary, and GI glands are strongly stimulated by parasympathetic nervous system.
They result in watery secretion . Sympathetic stimulation causes direct effect
on glands Secretion will be more mucous in nature and
less.
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GI - system
Has its own intrinsic set of nerves known as intra mural plexus or intestinal enteric nervous system.
Parasympathetic activity increases overall activity of GIT . Promotes peristalsis increased secretion of GI glands.
Sympathetic stimulation decreases its activity
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Heart
Sympathetic system increases rate and force of contraction of heart .
Parasympathetic system allows heart some degree of rest between its strenuous activity
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Effect of sympathetic stimulation
Pupils are dilated Ciliary muscles are relaxed for far vision Sweating is increased Blood vessel constriction HR increased Blood clotting increased Blood glucose levels are increased BMR increased
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Effect of Parasympathetic Stimulation
Pupils are constricted Ciliary muscles constricted for near vision Decreased HR Increased peristalsis tone and sphincter is
relaxed
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Pharmacology of ANS
Sympathomimetic drugs – adrenergic effecter drugs
Drugs that act on cholinergic effecter organs
Drugs that stimulate or block the sympathetic and parasympathetic post ganglionic neurons
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Drugs that act on Adregenic effecter organs
The symmpathomimetic drugs –
epinephrine,isoproternol
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Drugs that cause release of nor-epinephrine from nerve endings.
Ephedrine tryamine amphetamine Drugs that block Adregenic activity Propanalol metaprolol.
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Drugs that act on cholinergic organs
Parasympathomimetic drugs: pilocarpine, methacoline;
Drugs that have parasympathetic potentiating effect : Pyridostigmine & neostigmine
Drugs that block cholinergic activity at effector organ- antimuscrinic drugs: atropine & scolopmine
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DRUGS THAT STIMULATEOR BLOCK SYMPATHETIC & PARASYMPATHETIC POST GANGLION NEURONS
DRUGSTHAT STIMULATE AUTONOMIC POST GANGLIONIC NEURONS: ACETACHOLINE &METHACHOLINE
GANGLIONIC BLOCKING AGENT:HEXAMETHONIUM & PENTOLINIUM
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GANGLIA
THEY ARE COLLETIONS OF NERVE CELL BODIES LOCATED OUTSIDE THE CNS.
THERE ARE TWO TYPES OF GANGLIA 1) CRANIO-SPINAL 2) AUTONOMIC
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CRANIO-SPINAL
THEY ARE LOCATED IN THE DORSAL ROOTS OF 31 PAIRS OF SPINAL NERVE AND IN THE SENSORY ROOTS OF TRIGEMINAL , FACIAL, VESTIBULOCOCHLEAR, GLOSSOPHARYNGEAL AND VAGUS NERVE .
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AUTONOMIC
THEY ARE CLUSTERS OF NEURONS FOUND FROM THE BASE OF THE SKULL TO THE PELVIS , IN CLOSE ASSOCIATION WITH AND BILATERALY ARRANGED ADJACENTTO VENTRAL BODIES (SYMPATHETIC GANGLIA) , OR WITHIN THE ORGAN THEY INNERVATE (PARASYMPATHETIC).
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Ciliary ganglion
Peripheral parasympathetic ganglion lies near the apex of the orbit – between the optic nerve and the tendon of lateral rectus muscle
Has motor sensory and sympathetic roots Motor root arises from nerve to the inferior oblique . Pre –ganglionic fibers begin in EDINGER-WESTPAL
nucleus. Post-ganglionic fibers pass through short Ciliary
nerves and supply sphincter puppillae and Ciliary muscle
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Sensory root comes from the nasociliary nerve . It contains sensory fibers from the eye ball.
The fibers do not relay in the ganglion. The sym pathetic root is a branch from
internal carotid plexus . They supply blood vessels of eye ball.
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BRANCHES – the ganglion gives off 8 – 10 short ciliary nerve which divide into 15 -20 branches . They pierce the sclera around the optic nerve.
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Sub-mandibular ganglion
Relay station for secretomotor fibers to the sub-mandibular and sub-lingual salivary glands.
Topographically related to lingual nerve Functionally related to facial nerve. It lies on the hyoglossus muscle just above the deep
part of the sub-mandibular salivary gland, suspended from lingual nerve two roots
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Motor fibers pass from the lingual nerve to the ganglion through the posterior root
The pre-ganglionic fibers that arise in the superior salivatory nucleus and pass through facial nerve lingual nerve to reach the ganglion.
Postganglionic fibers reach the gland through 5-6 branches from the ganglion .
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Sympathetic fibers are derived from the plexus around facial artery .
Sensory fibers reach the ganglion through the lingual nerve with cell bodies in trigeminal ganglion.
Branches given to submandibular and sublingual glands via branches of lingual nerve.
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PTERYGOPALATINE GANGLION
LARGEST PARASYMPATHETIC PHERIPHARAL GANGLION
Relay station for secretomotor fibers to the lacrimal gland and to the mucous glands of the nose , Para nasal sinuses, the palate and the pharynx.
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Topographically it is related to the maxillary nerve
Functionally connected to facial nerve.
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The ganglion lies immediately in front of the opening of the pterygoid canal
Parasympathetic root from superior salivary nucleus by nerve of the pterygoid canal and the greater petrosal nerve from the nervus intermedius part of facial nerve.
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Sympathetic root from the superior cervical ganglion by the internal carotid nerve , deep petrosal nerve and the nerve of pterygoid canal.
Sensory root from a branch of maxillary nerve
Branches to the lacrimal gland via the zygomatic and lacrimal nerves , mucous glands in the nose ,nasopharynx and palate
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OTIC GANGLION
It lies between the tensor palati and the mandibular nerve , just below the foramen ovale .
It is the relay station for the parasympathetic secretomotor fibers to the parotid gland.
Parasympathetic root from the inferior salivary nucleus by the glossopharyngeal nerve and its tympanic branch to the tympanic plexus and then to the lesser petrosal nerve
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Sympathetic root from the superior cervical ganglion by fibers running with the middle menengial artery
Sensory root from the auriculotemporal nerve with cell bodies in the trigeminal ganglion.
Branches to the parotid gland via filaments of the auriculotemporal nerve.
Unlike the other three ganglia the otic ganglia has an additional somatic motor root , from the nerve to the medial pterygoid : the fibers pass through with out synapse to supply tensor tympani and tensor palati
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CARDIAC PLEXUSES
IT CONSISTS OF CRANIAL OUTFLOW OF PRE – GANGLIONIC FIBERS THAT LEAVE BRAIN VIA VAGUS NERVE
IT HAS THE MOST EXTENSIVE DISTRIBUTION OF PARASYMPATHETIC FIBERS 80%.
IT SENDS FIBERS TO SUPERFICIAL CARDIAC PLEXUS IN THE ARCH OF AORTA AND THE DEEP CARDIAC PLEXUS ANTERIOR TO THE BRANCHING OF TRACHEA.
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PULMONARY PLEXUS
IT IS LOCATED ANTERIOR AND POSTERIOR TO ROOTS OF THE LUNGS AND WITH IN THE LUNGS THEMSELVES
IT RECIVES PRE-GANGLIONIC FIBERS FROM THE VAGUS AND TRANSMIT POSTGANGLIONIC PARASYMPATHETIC FIBERS TO THE LUNGS AND BRONCHI
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PELVIC SPLANCHIC NERVES
THE SACRAL PARASYMPATHETIC OUT FLOW CONSISTS F PREGANGLIONIC FIBERS FROM VENTRAL ROOTS OF 2ND THROUGH 4TH SACRAL NERVES , COLLECTIVELY THEY FORM PELVIC SPLANCHIC NERVES
THE POST GAGLIONIC FIBERS ARE SENT TO COLON URINARY BLADDER AND REPRODUCTIVE ORGANS
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Somatic
Supply skeletal muscles Distal most synapse in CNS Myelinated Transmitter – acetylcholine Paralysis and atrophy of the muscles occurs
if supply is affected
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Autonomic
Supplies the organs Distal most synapse is outside CNS (ganglia) Preganglionic fibers are –Myelinated Postganglionic fibers are –non Myelinated Peripheral plexus formation is present Acetylcholine & nor adrenaline is
neurotransmitters Activity maintained
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YOUR JOYS AND YOUR SORROWS YOUR MEMMORIES AND YOUR AMBITIONS ARE INFACT NO MORE THAN THE VAST BEHAVIOUR OF THE VAST ASSEMBLY OF NERVE CELLS AND THEIR ASSOCIATED STRUCTURES
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REFERENCES
REVIEW OF MEDICAL PHYSIOLOGY 15TH Edition, William F Ganong
Textbook of MEDICAL PHYSIOLOGY 9TH edition, Guyton and Hall
Principles of Anatomy and Physiology 6th edition, Tortora
Functional Neuroanatomy, Adel
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