DENTAL & OPTOMETRYDENTAL & OPTOMETRYSTUDENTSSTUDENTS
INTRODUCTION TO INTRODUCTION TO AUTONOMIC NERVOUS SYSTEMAUTONOMIC NERVOUS SYSTEM
——
IE, SOMATIC NERVOUS SYSTEM IE, SOMATIC NERVOUS SYSTEM VERSUS AUTONOMIC NERVOUS VERSUS AUTONOMIC NERVOUS
SYSTEMSYSTEM
GEORGE SALTER, PH.DGEORGE SALTER, PH.D
DENTAL STUDENTSDENTAL STUDENTS
The Motor Aspect Of The The Motor Aspect Of The
Nervous System May BeNervous System May Be
Divided Into A Somatic Divided Into A Somatic PartPart
And An Autonomic PartAnd An Autonomic Part
SOMATIC NERVOUS SOMATIC NERVOUS SYSTEMSYSTEM
• TARGET ORGAN IS SKELETAL MUSCLETARGET ORGAN IS SKELETAL MUSCLE
• A SINGLE NEURON IS INVOLVEDA SINGLE NEURON IS INVOLVED
• THE ORIGIN OF THE SINGLE NEURON THE ORIGIN OF THE SINGLE NEURON IS THE CNS, SPECIFICALLY THE IS THE CNS, SPECIFICALLY THE ANTERIOR HORN CELLSANTERIOR HORN CELLS
PHLHAH
Anterior Horn Cell
Thoracic Cord
AUTONOMIC NERVOUS AUTONOMIC NERVOUS SYSTEMSYSTEM
FunctionallyFunctionally, , The Autonomic Nervous The Autonomic Nervous
SystemSystemMay Be Divided Into A May Be Divided Into A
SympatheticSympatheticPart And A Part And A ParasympatheticParasympathetic
Part.Part.
These Two “Divisions” Have These Two “Divisions” Have Opposite Effects—Eg. Opposite Effects—Eg.
SympatheticSympatheticFibers Increase The Heart Fibers Increase The Heart
Rate (Tachycardia) And The Rate (Tachycardia) And The Parasympathetic Fibers Parasympathetic Fibers
Decrease The Pulse Decrease The Pulse (Bradycardia).(Bradycardia).
ANS—Both Parasympathetic ANS—Both Parasympathetic &&
Sympathetic FibersSympathetic Fibers
• Target Organs Are Glands, Smooth Target Organs Are Glands, Smooth Muscle and Cardiac MuscleMuscle and Cardiac Muscle
Two Neurons, And Thus a Synapse, Are Two Neurons, And Thus a Synapse, Are
Involved Before Target Organ is ReachedInvolved Before Target Organ is Reached Origin Of The First Neuron Is The CNSOrigin Of The First Neuron Is The CNS
Origin of Neuron(Cell Body) No. 1
Parasympathetic Nervous Parasympathetic Nervous System,System,
(Or, Subdivision Of The(Or, Subdivision Of TheAutonomic Nervous Autonomic Nervous
System)System)
Parasympathetic Fibers Parasympathetic Fibers ExtendExtend ONLYONLY To The To The
Internal Organs—Internal Organs—Viscera- and eyes and Viscera- and eyes and
salivatory glands in head.salivatory glands in head.
PostganlionicNeuron
Preganglionic(Presynaptic)
Neuron(No. 1)
Postganglionic(Postsynaptic)
Neuron (No. 2)
Craniosacral Outflow
In or near organ supplied
L Colic Flexure
SACRALCORD
LEVELS
L Colic Flexure
BRAIN-STEM
C
O
P
S
COPS
BOTTOM LINEBOTTOM LINE
• (1) HOW MANY CRANIAL NERVES CARRY (1) HOW MANY CRANIAL NERVES CARRY PARASYMPATHETIC FIBERS?PARASYMPATHETIC FIBERS?
ANSWER: ANSWER: FourFour
(2) HOW MANY SPINAL NERVES CARRY (2) HOW MANY SPINAL NERVES CARRY • PARASYMPATHETIC FIBERS?PARASYMPATHETIC FIBERS?
ANSWER: ANSWER: ThreeThree
Sympathetic Nervous Sympathetic Nervous System,System,
(Or, Subdivision Of (Or, Subdivision Of The Autonomic The Autonomic
Nervous System)Nervous System)
ANS—Both Parasympathetic ANS—Both Parasympathetic &&
Sympathetic FibersSympathetic Fibers
• Target Organs Are Glands, Smooth Target Organs Are Glands, Smooth Muscle and Cardiac MuscleMuscle and Cardiac Muscle
Two Neurons Are Involved Before Target Two Neurons Are Involved Before Target
Organ is ReachedOrgan is Reached Origin Of The First Neuron Is The CNSOrigin Of The First Neuron Is The CNS
To Repeat what we said To Repeat what we said earlier,earlier,
BUT,BUT,Sympathetic Fibers Extend Sympathetic Fibers Extend
BothBoth To The Periphery To The Periphery (The Body Wall & Limbs) (The Body Wall & Limbs) AND AND to the Viscera, and to the Viscera, and therefore the Viscera are therefore the Viscera are
DuallyDuallyInnervated.Innervated.
PreganglionicNeuron
PostganlionicNeuron
Thoracolumbar Outflow
Origin and Distribution of Origin and Distribution of Sympathetic AxonsSympathetic Axons
• leave CNS ONLY between T1 & L2 leave CNS ONLY between T1 & L2 (thoracolumbar outflow). From (thoracolumbar outflow). From lateral horn cell bodies, pre-lateral horn cell bodies, pre-ganglionic axons pass into the ganglionic axons pass into the ventral root, spinal nerve,and ventral root, spinal nerve,and connect to the sympathetic trunk connect to the sympathetic trunk ganglia via white rami ganglia via white rami communicantes.communicantes.
Lateral Horn
WRC
Ventral Root
SympatheticTrunk Ganglion
Sp. N.
T1-L2
THENTHEN THE FIBERS, ONCE THE FIBERS, ONCE IN THE SYMPATHETIC IN THE SYMPATHETIC
TRUNK, MUST SYNAPSE TRUNK, MUST SYNAPSE IN EITHER :IN EITHER :
• The The ParavertebralParavertebral (Sympathetic Trunk) (Sympathetic Trunk) Ganglia OR,Ganglia OR,
• The The PrevertebralPrevertebral (Para-aortic) Ganglia (Para-aortic) Ganglia
SYMPATHETIC TR.WITH 2 CONNECTIONS TO SPINAL NERVES = RAMI COMMUNICANTES- White (lateral)& Gray (medial)
Paravertebral Ganglion(Sympathetic trunk Ganglion)
Lead to Prevertebral Ganglia
PREVERTEBRAL (OR)PREAORTIC
GANGLIAThese ganglia migrated
from paravertebral gangliaand dragged their presynaptic
G,L,& L splanchnic ns. with them.
(SYMP.)
Sympathetic Fibers Extend Sympathetic Fibers Extend BothBoth To The Periphery To The Periphery
(The Body Wall & Limbs) (The Body Wall & Limbs) AND AND to the Viscera, and to the Viscera, and
Therefore the Viscera are Therefore the Viscera are DuallyDually
Innervated.Innervated.
FundamentalsFundamentals
1) 31 pr. of spinal nerves supply the entire 1) 31 pr. of spinal nerves supply the entire surface of the body wall and limbs (recall surface of the body wall and limbs (recall
dermatomes)dermatomes) 2) Smooth muscle exists in every blood 2) Smooth muscle exists in every blood
vessel inferior to the cranial fossae and at the vessel inferior to the cranial fossae and at the basebase
of every hair follicle in the body.of every hair follicle in the body.3) Glands exist everywhere on the body 3) Glands exist everywhere on the body
surface.surface.
4)THEREFORE, SYMPATHETIC FIBERS 4)THEREFORE, SYMPATHETIC FIBERS REACH EVERY SQUARE INCH OF THE REACH EVERY SQUARE INCH OF THE
BODY SURFACE (PERIPHERY),BODY SURFACE (PERIPHERY),AND THEY ACCOMPLISH THIS BY AND THEY ACCOMPLISH THIS BY
COMMUNICATINGCOMMUNICATING WITH EVERY SPINAL NERVE WITH EVERY SPINAL NERVE
Big Picture Sympathetics:Big Picture Sympathetics:
1
2
• Sympathetic distribution – everywhere , both to the periphery (body wall and limbs) AND to the viscera
•All sympathetic fibers must enter sympathetic chain.
To go to the periphery , the fibers must extend from the symp. trunk
into EACH spinal nerve, by one of two means: either,
enter chain, then extend up/down, synapse and then follow GRC to spinal ns. at that level (which is a different level from that of the entry point—T1-L2)(Therefore), the only function of GRC is to carry postsynaptic fibers to every spinal nerve and therefore to the periphery (body wall and limbs).
• Sympathetic fibers use paravertebral chain (sympathetic chain) to
distribute both to (1) periphery and (2) viscera:
synapse in chain at same level, follow GRC to spinal n. or,
Implying they have to reach all spinal nerves (at, above, or below the level of entry)
TO THE PERIPHERY:
SPINAL N..
SPINAL N.
SPINAL N.
2
2
1
GRC
GRC
Origin
SYMPATHETICTRUNK
To Periphery below head
NOW, LET’S CONSIDER NOW, LET’S CONSIDER SYMPATHETIC FIBERS SYMPATHETIC FIBERS
TOTO THE HEAD THE HEAD
Sympathetic Trunk
Representing the smooth muscle & glands of head other than skin
ORIGINALLY, THERE WERE 8 CERVICAL SYMPATHETIC GANGLIA, ONE ASSOCIATED WITH EACH CERVICAL SPINAL NERVE. BUT, THESE GANGLIA COALESCED INTO 3 (4) GANGLIA. THEREFORE, THESE REMAINING CERVICAL SYMPATHETIC GANGLIA WERE LEFT TO SEND POSTSYNAPTIC FIBERS (VIA GRC) TO SEVERAL SPINAL NERVES EACH.
The sympathetic trunk is located posterior to the
carotid sheath on the prevertebral
fascia
K. Kryger
R. Common Carotid A
internal carotid a
I. Carotid npostgang. fibers
Superior Cervical Ganglion
(upper 4 ganglia)
Middle cervical ganglion
(ganglia 5 & 6)
Inferior cervical ganglion
(ganglia 7 & 8)
1st rib (cut)R. subclavian a. (cut)
hyoid
Ext. Carotid N.
Sympathetic fibers to the Head Sympathetic fibers to the Head would ascend as presynaptic would ascend as presynaptic
fibers to reach the most fibers to reach the most superior cervical sympathetic superior cervical sympathetic ganglion. Synapse would then ganglion. Synapse would then occur, and postsynaptic fibers occur, and postsynaptic fibers
would follow the arterial would follow the arterial branches (ECA & ICA) to reach branches (ECA & ICA) to reach the smooth muscle and glands the smooth muscle and glands of the head.Two large branches of the head.Two large branches (one, anyway) off the superior (one, anyway) off the superior
cervical ganglion are referred to cervical ganglion are referred to as the ECA and ICA nerves.as the ECA and ICA nerves.
The sympathetic trunk is located posterior to the
carotid sheath on the prevertebral
fascia
K. Kryger
R. Common Carotid A
internal carotid a
I. Carotid npostgang. fibers
Superior Cervical Ganglion
(upper 4 ganglia)
Ext. Carotid N.
Lateral horns of cord levels T1-2
superior cervical ganglion (in neck)
Target tissue
smooth muscle in vessel walls,
dilator pupillae m, & sweat glands.
Preganglionic axons ascendin the sympathetic trunk
Postganglionic axons distributed via Ext. & Int. carotid ns.( carotid plexus)
K. Kryger
Functions:
1) vasoconstriction
2) dilate pupils
3) stimulate sweat glandsPreganglionic fibres enter the
sympathetic trunk
Overview of Sympathetics to Overview of Sympathetics to HeadHead
Superior Cervical Ganglion
Sympathetic fibers to the head ascend in the sympathetic trunk and synapse in the superior cervical ganglion & then postganglionic fibers follow the ECA & ICA to reach the smooth muscle and glands of the head, including the eye.
Origin
NOW, LET’S CONSIDER NOW, LET’S CONSIDER SYMPATHETIC FIBERSSYMPATHETIC FIBERS
TO TO THETHE CERVICAL CERVICAL VISCERAVISCERA
Sympathetic fibers to the neck Sympathetic fibers to the neck viscera, eg. the pharynx, would viscera, eg. the pharynx, would ascend as presynaptic fibers to ascend as presynaptic fibers to reach the cervical sympathetic reach the cervical sympathetic ganglia. Synapse would then ganglia. Synapse would then
occur, and postsynaptic fibers occur, and postsynaptic fibers wouldwould
pass to the viscera via direct pass to the viscera via direct branches or via the blood vessels.branches or via the blood vessels.
Cervical Viscera
Origin
THE ENDTHE END