1. AUTONOMIC
NERVOUS SYSTEM
DR. SARAN AJAY
DEPT. OF PHYSIOLOGY, GMCM

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Complementary, my dear Watson!

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5. Autonomic system makes involuntary fine tuning
adjustments to your body according to the signals your
CNS is picking up.
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Specific Learning Objectives
• Introduction to ANS
• General Organisation of ANS
• Sympathetic System
• Parasympathetic System
• Neurotransmitters and Receptors in ANS
• Responses of various organs to autonomic nerve impulses
• Drugs acting on ANS
• Applied Physiology
• Summary
DEPT. OF PHYSIOLOGY, GMCM

7. Autonomic Nervous System
• Controls visceral functions.
• Maintains homeostasis.
• Rapidity and Intensity
Autonomic (adj) /ɔːtəˈnɒmɪk/
self governing, functionally independent
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8. OUTPUT FROM CNS
Somatic Motor
Neurons
Skeletal Muscle
Autonomic Motor
Neurons
Smooth Muscle
Cardiac Muscle
Secretory Epithelia
Exocrine Glands
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9. How does the ANS work?
Operates via the visceral reflex.
Viscera Integration
center in CNS
Receptor Afferent Pathway
Efferent Pathway
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10. Divisions of ANS
1. Sympathetic Nervous System
2. Parasympathetic Nervous System
3. Enteric Nervous System
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Specific Learning Objectives
• Introduction to ANS
• General Organisation of ANS
• Sympathetic System
• Parasympathetic System
• Neurotransmitters and Receptors in ANS
• Responses of various organs to autonomic nerve impulses
• Drugs acting on ANS
• Applied Physiology
• Summary
DEPT. OF PHYSIOLOGY, GMCM

12. Peripheral motor portions of ANS are made up of two neurons.
1. Preganglionic Neuron
2. Post Ganglionic Neuron
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14. ANS General Organization
Pre-ganglionic
Neuron
Post- ganglionic
Neuron
Target
Organ
Located in CNS Located in
peripheral ganglia
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15. Sympathetic and Parasympathetic system innervate target
tissues by two synapse pathway.
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17. Axons of the preganglionic neuron Axons of the postganglionic neuron
Myelinated , Small diameter
Slowly conducting B Fibers
Axons diverge onto the
postganglionic neuron
Unmyelinated
C Fibers
Axons terminate on visceral
effectors
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Specific Learning Objectives
• Introduction to ANS
• General Organisation of ANS
• Sympathetic System
• Parasympathetic System
• Neurotransmitters and Receptors in ANS
• Responses of various organs to autonomic nerve impulses
• Drugs acting on ANS
• Applied Physiology
• Summary
DEPT. OF PHYSIOLOGY, GMCM

19. Sympathetic Nervous System
• Cell bodies of the preganglionic neurons are in the
spinal cord.
• Intermediolateral column/ lateral horn
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21. Sympathetic Nervous System
• Cell bodies of the preganglionic neurons in the spinal cord.
• Intermediolateral column/ lateral horn
• Between T1 and L3/L4
• Thoracolumbar division of ANS
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22. Segmental Distribution of Sympathetic Fibers
T1 Head
T2 Neck
T3-T6 Thorax
T7-T11 Abdomen
T12, Lumbar Into Legs
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Sensory
afferent
Prevertebral
Ganglion

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25. Sympathetic Division
• Preganglionic axons exit through the ventral root.
• Along with axons from somatic motor neurons.
• After entering spinal nerve, sympathetic efferent diverge
from somatic motor axons.
• Enter White Rami Communicans
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26. Preganglionic
fibers
Paravertebral Ganglia
Prevertebral Ganglia
Direct Termination
Post ganglionic neurons
Post ganglionic neurons
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28. 1. Paravertebral Ganglia
• Extend from neck to coccyx
• One on either side of spinal cord
• Connected to each other
• Adjacent ganglia fuse
• e.g. – cervical, thoracic and lumbar ganglia
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29. In paravertebral ganglia, axons of preganglionic neurons
1. Synapse within same segmental paravertebral ganglia
2. Synapse within neighboring paravertebral ganglia
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30. 2. Prevertebral Ganglia
• Lies in front of aorta and its major branches
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32. 2. Prevertebral Ganglia
• Lies in front of aorta and its major branches
3. Terminate directly
• On effector organ – adrenal gland
• Postganglionic cell are secretory
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33. • Preganglionic sympathetic fibers without synapsing reach
adrenal medulla.
• The preganglionic fibres end on the secretory cells in
adrenal medulla
• The cells in adrenal medulla is postganglionic neurons
that lost their axon to become secretory cells.
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35. Axons of post ganglionic neurons leave the chain ganglia
• Re-enter spinal nerve via gray rami communicans
• Distributed to effectors in areas supplied by spinal nerves
• To smooth muscles, sweat glands
• Enter thoracic cavity
• Terminate on visceral organs
• Fibers from prevertebral ganglia terminate in visceral targets
1
2
3
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Specific Learning Objectives
• Introduction to ANS
• General Organisation of ANS
• Sympathetic System
• Parasympathetic System
• Neurotransmitters and Receptors in ANS
• Responses of various organs to autonomic nerve impulses
• Drugs acting on ANS
• Applied Physiology
• Summary
DEPT. OF PHYSIOLOGY, GMCM

38. Parasympathetic Nervous System
• Preganglionic Neurons are located in
1. Cranial Nerve Nuclei III, VII, IX and X
2. IML of the sacral spinal cord
• Craniosacral outflow
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39. Cranial Outflow
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40. • Parasympathetic sacral outflow supplies the pelvic
viscera via the sacral spinal nerves (2th to 4th).
• Fibers are in pelvic nerves.
• Post ganglionic neurons located in terminal ganglia.
Sacral Outflow
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41. • Ganglia - peripherally located, often within the walls
of target organs
• Distributed to
1. Descending colon, Rectum
2. Urinary bladder, lower portions of ureter
3. External genitalia
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Specific Learning Objectives
• Introduction to ANS
• General Organisation of ANS
• Sympathetic System
• Parasympathetic System
• Neurotransmitters and Receptors in ANS
• Responses of various organs to autonomic nerve impulses
• Drugs acting on ANS
• Applied Physiology
• Summary
DEPT. OF PHYSIOLOGY, GMCM

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45. • Varicosities/ bulbous expansions on axon
• Forms synapse en passant
• Wider distribution of autonomic output
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46. Synapse en passant
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47. Neurotransmitters and Receptors in ANS
• The principal transmitters are Acetylcholine (Ach) and
Norepinephrine (NE).
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48. 1. Between preganglionic and postganglionic neurons
(in both sympathetic and parasympathetic system)
• Neurotransmitter - Acetyl Choline
• Receptor - Nicotinic Receptor (N2)
(Ligand Gated Channel)
• Other sites - Neuromuscular Junction (N1)
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49. 2. Between postganglionic parasympathetic neurons
and target cell
• Neurotransmitter - Acetyl Choline
• Receptor - Muscarinic Receptor on target
(GPCR)
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50. Binding of ACh on muscarinic receptor can either stimulate
or inhibit functions of target cells.
Receptor Mechanism of Action
M1, M3, M5 (+) PL C, ↑ IP3 DAG
M2, M4 (-) adenyl cyclase, ↓ cAMP
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51. 3. Between postganglionic sympathetic neurons
and target cell
• Neurotransmitter - Norepinephrine
• Receptor - Adrenergic Receptors on
target (GPCR)
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52. Receptor Mechanism of Action
α1 (+) PL C, ↑ IP3 DAG
α2 ↓ cAMP
β1 ↑ cAMP
β2 ↑ cAMP
β3 ↑ cAMP
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53. 4. Exceptions
Sympathetic postganglionic fibers innervating
• Sweat Glands
• Piloerector muscles of hair
• Blood vessels in some skeletal muscle
ACh
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Specific Learning Objectives
• Introduction to ANS
• General Organisation of ANS
• Sympathetic System
• Parasympathetic System
• Neurotransmitters and Receptors in ANS
• Responses of various organs to autonomic nerve impulses
• Drugs acting on ANS
• Applied Physiology
• Summary
DEPT. OF PHYSIOLOGY, GMCM

56. Organs with
Dual innervation with antagonistic effects
e.g. Heart, Digestive tract, Urinary Bladder, Airways
Responses of various organs to autonomic
nerve impulses
1
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57. Complementary Sympathetic and Parasympathetic
Action
e.g. Salivary glands
2 Divisions act synergistically/ in cooperative manner
e.g. Control of pupil diameter, control of sexual function
2
3
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58. Organs innervated by only one division
e.g. Adrenal gland, most blood vessels, piloerector
muscles in skin, sweat glands – only sympathetic
supply
Lacrimal muscle, ciliary muscle and sublingual
salivary glands – only parasympathetic supply
4
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59. Sympathetic output can be
1. Selective for a specific target organ
2. Massive and non specific (fight or flight response)
Sympathetic Response
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60. Fight or Flight Response
• Walter B Cannon
• Fear, Stress etc. → massive output + PS activity ceases
• ↑ HR, BP, pupil dilation etc.
• Mechanism of survival
• Catabolic NS
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61. • Concerned with vegetative aspects of day to day living.
• Anabolic NS
Parasympathetic Response
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63. Effector Organ Parasympathetic
Sympathetic
Receptor Response
Eye
Radial muscle of iris - α1 Contraction
(Mydriasis)
Sphincter muscle of iris Contraction
(Miosis)
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64. Effector Organ Parasympathetic
Sympathetic
Receptor Response
Heart
SA Node ↓HR β1 ↑HR
Atria and ventricle ↓ atrial contractility β1, β2 ↑Contractility
AV Node and Purkunjee ↓ conduction velocity β1 ↑ conduction
velocity
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65. Effector Organ Parasympathetic Sympathetic
Receptor Response
Stomach and Intestine
Motility and Tone ↑ α 1, α 2, β2 ↓
Sphincters Relaxation α 1 Contraction
Secretion Stimulation - -
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66. Effector Organ Parasympathetic
Sympathetic
Receptor Response
Bronchial Smooth
Muscle
Contraction β2 Relaxation
Urinary Bladder
Detrusor Contraction β2 Relaxation
Sphincter Relaxation α1 Contraction
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67. Effector Organ Parasympathetic
Sympathetic
Receptor Response
Uterus (pregnant) α1/β2 Contraction/
Relaxation
Male sex Organs Erection α1 Ejaculation
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68. Effector Organ Parasympathetic Sympathetic
Receptor Response
Salivary Gland Profuse watery
secretion
α1/ β Thick,
viscous
secretion,
amylase
secretion
Lacrimal Gland Secretion - -
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Specific Learning Objectives
• Introduction to ANS
• General Organisation of ANS
• Sympathetic System
• Parasympathetic System
• Neurotransmitters and Receptors in ANS
• Responses of various organs to autonomic nerve impulses
• Drugs acting on ANS
• Applied Physiology
• Summary
DEPT. OF PHYSIOLOGY, GMCM

70. 1. Sympathomimetic drugs
• Stimulate specific adrenergic receptors
• e.g. Phenylephrine, Isoproterenol, Albuterol
Drugs acting on ANS
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71. 2. Parasympathomimetic drugs
• e.g. Pilocarpine, Methacholine
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Specific Learning Objectives
• Introduction to ANS
• General Organisation of ANS
• Sympathetic System
• Parasympathetic System
• Neurotransmitters and Receptors in ANS
• Responses of various organs to autonomic nerve impulses
• Drugs acting on ANS
• Applied Physiology
• Summary
DEPT. OF PHYSIOLOGY, GMCM

73. Horner’s Syndrome
Characterized by unilateral
1. Ptosis
2. Miosis
3. Anhidrosis
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74. • Loss of sympathetic innervation on one side of the face
• Causes
1. Malignancy of cervical Lymph Nodes
2. Pancoast Tumor
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Specific Learning Objectives
• Introduction to ANS
• General Organisation of ANS
• Sympathetic System
• Parasympathetic System
• Neurotransmitters and Receptors in ANS
• Responses of various organs to autonomic nerve impulses
• Drugs acting on ANS
• Applied Physiology
• Summary
DEPT. OF PHYSIOLOGY, GMCM

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77. SYMP Pre
Ganglionic
SYMP Post
Ganglionic
PARASYMP Pre
Ganglionic
PARASYMP Post
Ganglionic
Location of
cell body
Myelination
NT
Post Synaptic
Receptor
IML of SC
T1 to
L3/L4
Pre + Para
Vertebral
Ganglion
Brainstem
Sacral SC
Terminal
ganglion
near target
Yes Yes
No No
ACh ACh ACh
NE
Nicotinic Nicotinic
Adrenergic Muscarinic
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79. saran.adhoc@gmail.com
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