Understanding the basic physiology of autonomic nervous system.

1. AUTONOMIC NERVOUS
SYSTEM

2. PERIPHERAL NERVOUS SYSTEM
Sensory Motor
Somatic motor Autonomic nervous system
Skeletal muscles
Smooth muscles, Cardiac muscle
& glands exocrine and endocrine both

3. Salient features
 The organs innervated by the ANS are not
entirely dependent on nerve supply for their
activities(they have an autonomous activity of
their own).
 Innervation by ANS only serves to modulate the
activity of these organs. Eg.- heart continues to
beat even after denervation.
 Organs supplied by ANS are involuntary.

4. Somatic Motor System Autonomic Nervous System
Innervates skeletal muscle. Innervates smooth muscles,
cardiac muscle & glands (exocrine
and endocrine)Final common pathway in the
anterior column of the spinal
cord.
Final common pathway outside
the central nervous system in
autonomic ganglia.
Well directed synapse between
nerve ending and muscle(NMJ)
Non-directed synapse between
nerve ending and the innervated
organ.
Controls voluntary
movements.
Modulate involuntary activities
.
(Visceral, Cardiac &
Glandular)
Skeletal muscle activity is entirely
dependent on nerve supply.
Only modulation done by ANS.
Organs show autonomy.Activity specifically localized
to certain muscle groups.
Activity may be generalized.
COMPARISON BETWEEN
SOMATIC MOTOR AND AUTONOMIC NERVOUS
SYSTEM

5. Segmental distribution of sympathetic nerves
T-1 pass up to sympathetic chain and terminate in the
head.
T-2 terminate in neck.
T-3,4,5 &6 in to thorax
T-7,8,9,10,11 in to abdomen.
T-12, L-1&2 in to legs.

7. Distribution of Parasympathetic System
It is known as Craniosacral autonomic system.
Parasympathetic fibers leave
 from CNS through III, VII, IX and X nerves.
 from Sacral region S2 &3 mainly.

9. Neurotransmitters
ANS secretes two types of neurotransmitters
Acetylcholine & Nor-epinephrine.
Those nerves secrete acetylcholine k/as
Cholinergic
Those nerves secrete Nor-epinephrine k/as
Adrenergic.
All pre ganglionic fibers of ANS are Cholinergic.
All post ganglionic parasympathetic fibers are
Cholinergic.
Most of the post ganglionic sympathetic fibers are
adrenergic except supplying sweat glands,
piloerector muscle and a very few blood vessels.

11. COMPARISON BETWEEN
SYMPATHETIC AND PARASYMPATHETIC NERVOUS SYSTEM
Sympathetic Parasympathetic
Site of pre-
ganglionic
Neurons
Thoracolumber
Segment
(Segment T1-L3)
Craniosacral (Nuclei of Cranial
nerves III, VII, IX & X and
Segment S2-4).
Site of
Ganglia
Prevertebral and Para
vertebral ganglia.
Within or very close to the
organ innervated.
Preganglio
nic
neurons
Cholinergic Cholinergic
Post-
ganglionic
neurons
Adrenergic
(Exceptions in sweat
glands cholinergic)
Cholinergic
Activation In Emergencies and
REM
Sleep
When relaxed and in slow
wave sleep.
Effects Useful in
emergencies.
Substrate mobilized
for providing energy.
Catabolic and
Thermogenic
Useful at rest.
Substrates deposited for
storage.
Anabolic.

13. Synthesis of Ach-
Acetyl-CoA+ Choline Acetylcholine.
Destruction by Acetylcholinesterase in to Acetate ion
and Choline.
Choline is transported back.
Synthesis of Norepinephrine-
Tyrosine Dopa.
Dopa Dopamine.
Transport of Dopamine in to vesicles.
Dopamine Norepinephrine.
Hydroxylation
Decarboxylation
In Axoplasm
Hydroxylation

14. Receptors
Parasympathetic—
Muscarinic
Nicotinic.
Muscarinic found on all effector cells that are
stimulated by postgnglionic cholinergic
neurons.(both divison)
Nicotinic are found in autonomic ganglia at the
synapse between preganglionic and post
ganglionic neurons of both division.

15. Adrenergic receptors
Two major types
Alpha & Beta.
Alpha are of two types
Alpha 1 & Alpha 2.
Beta 1, Beta 2& Beta3.
Norepinephrine and epinephrine both of which
secreted from adrenal medulla have slightly different
effect in exciting these receptors.
Norepinephrine excites mainly alpha receptor but
epinephrine excites both receptors.

17. Organ Sympathetic stimulation Parasympathetic
stimulation
Heart Increased rate & force of
contraction.
Decrease in rate and
force of contraction
Lung Bronchodilation Bronchoconstriction
Gastrointestin
al tract
Decrease in motility, tone
and secretion &
contraction of sphincters.
Increase in motility ,
tone and secretion.
Bladder Relaxation of detrusor,
Contraction of sphincters
Contraction of detrusor,
Relaxation of
sphincters.
Blood vessels Splanchnic and cutaneous
vasoconstriction.
Cholinergic & adrenergic β2
receptors gives
vasodilation.
None
Eye Pupillary dilation,
relaxation of ciliary
muscle.
Pupillary
constriction,
contraction of ciliary
muscle.
Sweat glands Sweating ( Cholinergic) Sweating on palms
only.
Metabolic
effects
Glycogenolysis, Lipolysis Not significant.
AUTONOMIC EFFECTS ON VARIOUS ORGANS

18. Functions of Adrenal Medullae
 Secretions from Adrenal medulla causes release of
epineprine and norepinephrine in blood.
 80% of secretion is Epinephrine and rest is
Norepinephrine.
 Effect of these epinephrine & Norepinephrine lasts for
about 5-10 times longer then when released by
sympathetic stimulation.
 Circulating norepinephrine causes vasoconstriction,
increased HR & contractility, inhibition of
gastrointestinal tract and dilated pupil.
 Circulating epinephrine cause greater effect on heart
as they act through β-receptors causing weak
constriction of blood vessels but dramatic increase in
CO.

19. Sympathetic & parasympathetic tone
Basal rate of activity of ANS is K/as tone of each
segment.
Sympathetic tone and parasympathetic tone
allow a single division of the ANS to increase or
decrease the activity of a visceral organ or to
constrict or dilate a vascular bed.
Discrete OR Mass discharge of ANS
Alarm or Stress response due to generalized activation of
sympathetic nervous system.
Other times sympathetic activation occurs in isolated area of the body
like local vasodilation and sweating.
Parasympathetic response is usually responsible for highly specific
changes in
visceral fuctions.

20. Control of autonomic activity
 Many neuronal areas in brain stem
 Reticular formation
 Along the course of the tractus solitarius of the
medulla, pons and mesencephalon.
Signals from hypothalamus and even from
cerebrum influence the activities of almost all
the brainstem autonomic control centers.

22. Drugs affecting ANS
Adrenergic drugs (Sympathomimetic Drugs)
Act like epinephrine and norepinephrine.
Most of these drugs have a duration of action of about 30min to 2hours.
Drugs act on receptors- Phenylephrine(α), Isoproteronol(β1 & β2),
Albuterol(β2).
Drugs Inducing release of norepineprine from nerve terminals-
ephedrine, tyramine & amphetamine.
Drugs that block Adrenergic activity-
Blockage of synthesis and storage- resepine.
Block the release of norepinephrine- guanethidine.
Blocks the adrenergic receptor- α receptor phenoxybenzamine &
phentolamine. Β receptor blocker- propranolol.

23. Drugs that act on Cholinergic effector organs
are parasympathomimetic or muscarinic drugs-
pilocarpine.
Drugs that prolonged the activity of acetylcholine by
blocking acetylcholinesterase-
neostigmine, pyridostigmine and ambenonium.
Drugs that block cholinergic activity are
antimuscarinic drugs- atropine, homatropine &
scopolamine.
Drugs that block impulse transmission from
preganglionic to postganglionic neurons- tetraethyl
ammonium ions, hexamethonium & pentolinium.

24. Applied
 Organophosphate: pesticide and nerve gas
poisoning.
 Mushroom poisoning/Mycetism.
 Dhatura poisoning.
 Horner’s syndrome.
 Raynaud’s phenomenon.