2. DENTAL & OPTOMETRY STUDENTS

5. INTRODUCTION TO AUTONOMIC NERVOUS SYSTEM— IE, SOMATIC NERVOUS SYSTEM VERSUS AUTONOMIC NERVOUS SYSTEM
GEORGE SALTER, PH.D
DENTAL STUDENTS

6. The Motor Aspect Of The Nervous System May Be Divided Into A Somatic Part And An Autonomic Part

8. SOMATIC NERVOUS SYSTEM
TARGET ORGAN IS SKELETAL MUSCLE
A SINGLE NEURON IS INVOLVED
THE ORIGIN OF THE SINGLE NEURON IS THE CNS, SPECIFICALLY THE ANTERIOR HORN CELLS

9. Thoracic Cord PH LH AH
Anterior Horn Cell

11. AUTONOMIC NERVOUS SYSTEM

12. Functionally, The Autonomic Nervous System May Be Divided Into A Sympathetic Part And A Parasympathetic Part. These Two “Divisions” Have Opposite Effects—Eg. Sympathetic Fibers Increase The Heart Rate (Tachycardia) And The Parasympathetic Fibers Decrease The Pulse (Bradycardia).

13. ANS—Both Parasympathetic & Sympathetic Fibers
Target Organs Are Glands, Smooth Muscle and Cardiac Muscle
Two Neurons, And Thus a Synapse, Are Involved Before Target Organ is Reached
Origin Of The First Neuron Is The CNS

15. Origin of Neuron
(Cell Body) No. 1

16. Parasympathetic Nervous System, (Or, Subdivision Of The Autonomic Nervous System)

17. Parasympathetic Fibers Extend ONLY To The Internal Organs— Viscera- and eyes and salivatory glands in head.

18. Craniosacral Outflow Postganlionic Neuron Postganglionic
(Postsynaptic)
Neuron
(No. 2)
Preganglionic
(Presynaptic)
Neuron
(No. 1)
Craniosacral Outflow

19. In or near organ supplied

20. L Colic Flexure
SACRAL
CORD
LEVELS

21. S C P
BRAIN-
STEM O
COPS
L Colic Flexure

22. BOTTOM LINE (1) HOW MANY CRANIAL NERVES CARRY PARASYMPATHETIC FIBERS?
ANSWER: Four
(2) HOW MANY SPINAL NERVES CARRY
PARASYMPATHETIC FIBERS?
ANSWER: Three

23. Sympathetic Nervous System, (Or, Subdivision Of The Autonomic Nervous System)

24. ANS—Both Parasympathetic & Sympathetic Fibers
To Repeat what we said earlier,
ANS—Both Parasympathetic & Sympathetic Fibers
Target Organs Are Glands, Smooth Muscle and Cardiac Muscle
Two Neurons Are Involved Before Target Organ is Reached
Origin Of The First Neuron Is The CNS

25. BUT, Sympathetic Fibers Extend Both To The Periphery (The Body Wall & Limbs) AND to the Viscera, and therefore the Viscera are Dually Innervated.

26. Thoracolumbar Outflow
Preganglionic
Neuron
Postganlionic
Neuron
Thoracolumbar Outflow

27. Origin and Distribution of Sympathetic Axons
leave CNS ONLY between T1 & L2 (thoracolumbar outflow). From lateral horn cell bodies, pre-ganglionic axons pass into the ventral root, spinal nerve,and connect to the sympathetic trunk ganglia via white rami communicantes.

28. Lateral Horn
T1-L2
Sp. N.
Ventral Root
Sympathetic
Trunk Ganglion
WRC

29. THEN THE FIBERS, ONCE IN THE SYMPATHETIC TRUNK, MUST SYNAPSE IN EITHER :
The Paravertebral (Sympathetic Trunk) Ganglia OR,
The Prevertebral (Para-aortic) Ganglia

30. SYMPATHETIC TR.
WITH 2 CONNECTIONS TO SPINAL NERVES = RAMI COMMUNICANTES- White (lateral)
& Gray (medial)

31. Paravertebral
Ganglion
(Sympathetic trunk Ganglion)

32. Lead to Prevertebral
Ganglia

33. These ganglia migrated from paravertebral ganglia
(SYMP.)
PREVERTEBRAL (OR)
PREAORTIC
GANGLIA
These ganglia migrated
from paravertebral ganglia
and dragged their presynaptic
G,L,& L splanchnic ns. with them.

34. Sympathetic Fibers Extend Both To The Periphery (The Body Wall & Limbs) AND to the Viscera, and Therefore the Viscera are Dually Innervated.

35. Fundamentals 1) 31 pr. of spinal nerves supply the entire surface of the body wall and limbs (recall dermatomes) 2) Smooth muscle exists in every blood vessel inferior to the cranial fossae and at the base of every hair follicle in the body. 3) Glands exist everywhere on the body surface. 4)THEREFORE, SYMPATHETIC FIBERS REACH EVERY SQUARE INCH OF THE BODY SURFACE (PERIPHERY), AND THEY ACCOMPLISH THIS BY COMMUNICATING WITH EVERY SPINAL NERVE

36. Big Picture Sympathetics:
Sympathetic distribution – everywhere , both to the periphery (body wall and limbs) AND to the viscera
All sympathetic fibers must enter sympathetic chain.
Sympathetic fibers use paravertebral chain (sympathetic chain) to
distribute both to (1) periphery and (2) viscera:
To go to the periphery , the fibers must extend from the symp. trunk
into EACH spinal nerve, by one of two means: either,
synapse in chain at same level, follow GRC to spinal n. or, 1
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). 2

37. SPINAL N. 2 SPINAL N.. 2 TO THE PERIPHERY:
Implying they have to reach all spinal nerves (at, above, or below the level of entry)
SPINAL N. 2
GRC
SPINAL N..
Origin 1
SPINAL N. 2
GRC

38. To Periphery below head
SYMPATHETIC
TRUNK

39. NOW, LET’S CONSIDER SYMPATHETIC FIBERS TO THE HEAD

40. Representing the smooth muscle & glands of head other than skin
Sympathetic Trunk

41. 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.

42. I. Carotid n
postgang. fibers
The sympathetic trunk is located posterior to the carotid sheath on the prevertebral fascia
Superior Cervical Ganglion
(upper 4 ganglia)
Ext. Carotid N.
internal carotid a
hyoid
Middle cervical ganglion
(ganglia 5 & 6)
Superior cervical ganglion – found at the levels of C2&3 vertebrae
Middle cervical ganglion – found at C6 vertebra
Inferior cervical ganglion – found between the base of the TP of C7 vertebra & neck of the 1st rib
Inferior cervical ganglion
(ganglia 7 & 8)
R. Common Carotid A
1st rib (cut)
R. subclavian a. (cut)
K. Kryger

43. Sympathetic fibers to the Head would ascend as presynaptic fibers to reach the most superior cervical sympathetic ganglion. Synapse would then occur, and postsynaptic fibers would follow the arterial branches (ECA & ICA) to reach the smooth muscle and glands of the head.Two large branches (one, anyway) off the superior cervical ganglion are referred to as the ECA and ICA nerves.

44. I. Carotid n
postgang. fibers
The sympathetic trunk is located posterior to the carotid sheath on the prevertebral fascia
Superior Cervical Ganglion
(upper 4 ganglia)
Ext. Carotid N.
internal carotid a
Superior cervical ganglion – found at the levels of C2&3 vertebrae
Middle cervical ganglion – found at C6 vertebra
Inferior cervical ganglion – found between the base of the TP of C7 vertebra & neck of the 1st rib
R. Common Carotid A
K. Kryger

45. Overview of Sympathetics to Head
Postganglionic axons distributed via Ext. & Int. carotid ns.( carotid plexus)
Target tissue
smooth muscle in vessel walls,
dilator pupillae m, & sweat glands.
superior cervical ganglion
(in neck)
Preganglionic axons ascend
in the sympathetic trunk
Functions:
1) vasoconstriction
2) dilate pupils
3) stimulate sweat glands
Preganglionic fibres enter the sympathetic trunk
Lateral horns of cord levels T1-2
K. Kryger

46. 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.
Superior Cervical Ganglion
Origin

47. NOW, LET’S CONSIDER SYMPATHETIC FIBERS TO THE CERVICAL VISCERA

48. Sympathetic fibers to the neck viscera, eg
Sympathetic fibers to the neck viscera, eg. the pharynx, would ascend as presynaptic fibers to reach the cervical sympathetic ganglia. Synapse would then occur, and postsynaptic fibers would pass to the viscera via direct branches or via the blood vessels.

49. Cervical Viscera
Origin

50. THE END