Autonomic nervous system

1. AUTONOMIC NERVOUS SYSTEM
Dr. Chintansinh Parmar, MD (PHYSIOLOGY)

2. ANS is having two major classes of
functions:
Rest & Digest
Fight & Flight
totally opposite to each other

3. Autonomic
nervous
system
Sympathetic
(thoracolumbar
outflow)
Parasympathetic
(craniosacral outflow)
Cranial
outflow
Sacral
outflow

4. SYMPATHETIC NERVOUS SYSTEM
Old observation that injury produces tachycardia, as
if the tachycardia occur in sympathy to the
injury/blood loss, led to this naming
Originate in the spinal cord between segments
T1 & L2. so called Thoracolumbar division.
↓
pass in to chain of ganglion called paravertebral
ganglion or sympathetic chain
↓
tissues and organs

5. The postganglionic neurons in the paravertebral ganglia mainly
influence targets in the skin, like the erector pili muscles and blood
vessels and glands.

6. sympathetic chainsympathetic chain
↓
Any one of the following will be the route……..
1. synapse with postganglionic neurons in the
ganglion of the same from which it enters.
2. It can go up or down in the chain and synapse in
one of the other ganglion of the chain
3. It can pass for certain distances through the chain &
then synapse into peripheral ganglion or collateral
ganglion.

7. Postganglionic fibres (after the ganglia)
unmyelinated fibres so look gray
Post ganglionic fibres originate either from
sympathetic chain or peripheral / Collateral
ganglion.
Travel to the concern organ.

8. to influence the deeper visceral organs, like heart, kidneys,heart, kidneys,
and digestive systemand digestive system

11. SYMPATHETIC GANGLIA
Synapse between pre and postganglionic fibres
Following groups of ganglia occurs…..
1. The sympathetic trunk
A chain of ganglia situated immediately lateral to
vertebral column extending from neck to coccyx.
2 chains each having 22 ganglia connected
together with fibres.

12. STELLATE GANGLION
There are 3 cervical ganglia in the sympathetic trunk
Superior
Middle
Inferior
- The inferior cervical ganglion often fuses with first
thoracic ganglion and the resultant fused ganglion is
called stellate (star shaped) ganglion.
- stellate ganglion is particularly common in animals

13. 2. Prevertebral ganglion
 Also called collateral ganglion, situated in relation to abdominal
aorta & its branches.
 Three are known lie away from the spinal cord, closer to the
innervated organ.
(a) Celiac or solar
- situated near the origin of celiac artery
(b) Superior mesenteric – situated near the
origin of sup. Mesenteric artery
(c) Inferior mesenteric – situated near the
origin of inf. Mesenteric art.
3. Terminal ganglia lie near the bladder & rectum.

14. Structure of sympathetic ganglion
pre and post ganglionic fibres synapse
one preganglionic fibre synapse with many
postganglionic neurons and so stimulation of even
a few thoracolumbar lateral horn cells can produce
generalized activation of post ganglionic fibres.
in contrast…
parasymp. one pre to one post except vagus in
intestine

15. Why effects of sympathetic nervous system more
wide spread & long lasting ?
1. There is more divergence of the sympathetic
fibres.
2. NE remains in the synaptic cleft for a longer time
than does Ach.
3. NE, Epi secreted by adrenal medulla so it affect
most of the organs which have receptors.

16. Sympathetic nerve fibres in skeletal muscle
Some of the postganglionic fibres pass back from the
sympathetic chain to the spinal nerve
Very small C fibres
Extend to all parts of the body in the skeletal nerves
(about 8% fibers)
Control blood vessels, sweat glands, piloerector
muscles of the hairs

17. Sympathetic nerve endings in
the adrenal medullae
Some preganglionic fibres pass all the
way from the lateral horn of the spinal
cord  splanchnic nerve  adrenal
medulla
Ends directly on the modified neuronal
cells in adrenal medulla that secrete
nor-epinephrine,
epinephrine.

18. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
PARASYMPATHETICPARASYMPATHETIC
NERVOUS SYSTEMNERVOUS SYSTEM
 Leaves CNS through cranial nerves III, VII, IX, X; and lower
part of the spinal cord through S2 and S3.occasionally S1,S4.
CRANIAL OUTFLOW:
Edinger Westphal nucleus (III oculomotor nerve)
in midbrain
Superior Salivary Nucleus (VII facial) in lower part of
pons
Inferior Salivary Nucleus (IX glossopharyngeal nerve)
in upper part of medulla
Dorsal Nucleus of the Vagus (X Vagus) situated in the
medulla

19. Xth cranial nerve  Vagus
75% fibres are parasympathetic
supplies heart, lungs, esophagus, stomach, entire
small intestine, proximal half of colon, liver, gall
bladder, pancreas, upper portion of uterus.
IIIrd cranial nerve
pupillary sphincters and ciliary muscles of eye
VIIth cranial nerve
 lacrimal, nasal and submandibular glands
IXth cranial nerve
parotid gland

20. SACRAL OUTFLOW:
 From the lateral horn of the sacral segment
fibres come out to form ‘pelvic splanchnic
nerve’
The preganglionic fibres of parasympathetic
system pass uninterrupted to the organs which
are controlled.
The postganglionic neurons of parasympathetic
nerve fibres are located in the walls of the
organs and they are very short ( in mm or few
cm) and they innervate the tissue of the organs

21. The preganglionic fibres of parasympathetic
system pass uninterrupted to the organs which
are controlled.
The postganglionic neurons of
parasympathetic nerve fibres are located in the
walls of the organs and they are very very
short ( in mm or few cm) and they innervate
the tissue of the organs

24. Important notes
1. Sympathetic Nervous System
Preganglionic fibres  short &
Use NT acetylcholine
Postganglionic fibres  long &
Use NT noradrenalin
2. in Parasympathetic Nervous System
Preganglionic fibres  long &
Use NT acetylcholine
Postganglionic fibres  short &
Use NTacetylcholine

27. CHOLINERGIC NEURONSCHOLINERGIC NEURONS
secrete Ach
1)All preganglionic autonomic neurons.
just like motor neurons, cell bodies in spinal cord……
2) Postganglionic parasympathetic endings.
3) Postganglionic sympathetic endings.
supplying to the sweat glands and skeletal muscles blood vessels
(sympathetic vasodilator nerve).
Most of the postganglionic neurons are adrenergic
however
those which serve the sweat glands are in fact cholinergic in their action (i.e.
they use the neurotransmitter acetylcholine) except those on the palms of the
hands which are adrenergic.
This accounts for those people who get sweaty palms if they are
nervous or under stress!
4) Neuromuscular junction
5) Some parts of the brain, spinal cord.
6) Endings of some amacrine cells in the retina.

28. SYNTHESIS OF ACETYLCHOLINESYNTHESIS OF ACETYLCHOLINE
Choline + acetyl coenzyme A (active acetate)
↓ choline acetylase
acetylcholine
Stored in vesicles
After release destroyed by choline esterase
Two types (1) acetyl choline esterase
( true choline esterase)
- found in places where A-ch found
normally neuromuscular junction, ganglion, synapses.
(2) pseudo cholinesterase
- found in liver, plasma

29. Receptors of Ach :-Receptors of Ach :-
Two types
Nicotinic receptors
Nicotinic receptors are activated by nicotine found in
tobacco. In fact many of the effects of tobacco smoking can
be explained by the effects of nicotine.
 ACTION INHIBITED by hexamethonium, tubocurine.
Muscarinic receptors
because they are activated by muscarine which is a
poisonous drug found in certain mushrooms.
 Blocked by atropine.

32. Review of Efferent Pathways: Motor & Autonomic

33. (2) ADRENERGIC NEURONS(2) ADRENERGIC NEURONS
→ secreting Nor epinephrine / Epinephrine at their nerve endings
1) post ganglionic sympathetic endings
2) Hypothalamus
3) Cerebellum
4) Brainstem
5) spinal cord
6) adrenal medulla
7) cortex
→ catecholamines mean …
- adrenalin (Ad)
- noradrenalin (NA)
- dopamine (DA)

34. SYNTHESIS OF NOREPINEPHRINSYNTHESIS OF NOREPINEPHRIN
L- tyrosine
↓ tyrosine hydroxylase
L DOPA (dihydroxy Phenyl alanine)
↓
dopamine
↓
NA

35. Removal
85% released goes back to same nerve
terminal (reuptake)
- more selective to NA.
- blocked by amphetamine. So ↑se sympathetic
action.
 15% enters within cells of organ
 by two enzymes
(i) COMT (catechol O methyl transferase)
(ii) MAO (monoamine oxidase)

36. Adrenalin (Epinephrine)Adrenalin (Epinephrine)
synthesized by adrenal medulla
& not by postganglionic fibres
some neurons of the brain.

37. Β1 found on heart muscle and in certain cells of the kidney
B2 found in certain blood vessels, smooth muscle of airways; found where sympathetic
neurons ARE NOT
A1 receptors are found most commonly in sympathetic target tissues
A2 receptors are found in the GI tract and pancreas (relaxation)

38. EFFECTS OF ANS STIMULATION
Effector
Organ
Autonomic
Division
Type of
Receptor
Action
Eye : pupil Sympathetic
Parasympath
etic
alpha
muscarinic
dilation of
the pupil
constriction
of the pupil

39. Lacrimal
(tear)glands
sympathetic
Para
sympathetic
beta
muscarinic
vasoconstriction
secretion of tears
Salivary
glands
sympathetic
Para
sympathetic
alpha
muscarinic
vasoconstriction and
secretion of mucous
with a low enzyme
count
secretion of watery
saliva with a high
enzyme count

40. Heart
sympathetic
Para
sympathetic
beta
alpha
muscarinic
dilation of coronary arteries,
increased heart rate,
increased force of contraction,
increased rate of pacemaker
conduction
coronary artery constriction
slows, heart rate, reduces
contraction and conduction,
constricts coronary arteries

41. Bronchii
sympathetic
Para
sympathetic
beta
muscarinic
dilation
constriction and mucous
secretion
Oesophagus
sympathetic
Para
sympathetic
alpha
muscarinic
vasoconstriction
peristalsis, secretion of
mucous

42. Stomach and
Intestines
sympathetic
Para
sympathetic
beta
alpha
muscari
nic
inhibition of peristalsis
and secretion
vasoconstriction,
spinctre contraction
peristalsis and secretion

43. Spleen sympathetic alpha contraction
Adrenal
medulla
sympathetic -
adrenaline and noradrenaline
secreted into the bloodstream
Liver sympathetic beta
break down of glycogen
(glyogenolysis)

44. Gall
Bladder
sympathetic
Para
sympathetic
beta
muscarinic
relaxation
contraction
Pancreas sympathetic
alpha
beta
inhibition of insulin
secretion
stimulation of insulin
secretion

45. Descending colon
sympathetic
Para
sympathetic
alpha
beta
muscarinic
vasoconstriction
inhibition of peristalsis and
secretion
peristalsis and secretion
Sigmoid colon,
rectum and anus
sympathetic
Para
sympathetic
alpha
beta
Muscarinic
constriction of sphincter
muscles
inhibition of peristalsis and
secretion
peristalsis and secretion

46. Bladder
sympathetic
parasympathetic
alpha
beta
muscarinic
contraction of sphincter
relaxation of detrusor
muscle
contraction of detrusor
muscle
Penis
sympathetic
parasympathetic
-
muscarinic
ejaculation
erection
Clitoris parasympathetic muscarinic erection

47. Uterus sympathetic
alpha
beta
contraction
relaxation

48. Blood vessels in:
Skin sympathetic alpha constriction
Mucosal linings sympathetic alpha constriction
Muscle sympathetic cholinergic dilation
Kidneys sympathetic alpha constriction
Lungs sympathetic alpha constriction
Intracranial sympathetic alpha slight constriction

49. sweat glands except palm
of hands
sympathetic muscarinic sweating
sweat glands on palms of
hands
sympathetic alpha sweating

50. Piloerector
muscles at root
of body hair
sympathetic alpha
piloerection (making hair
"stand on end")
horripilation ("goose
pimples")
Adipose tissue sympathetic beta
lipolysis (break down of
fat to release energy)

51. FUNCTIONS OF ANSFUNCTIONS OF ANS
Parasympathetic nervous system is also called
Anabolic nervous system.
It is also called nerves of tomorrow.
Because this system favors the vegetative aspect of
living. Eg. Digestion, secretion
thus it helps to store the energy for the future use.
Parasympathetic nervous system is sometimes called
as Tropotropic nervous system.
i.e. growth promoting.

52.  sympathetic nervous system also known as
“Nerves of today”.
It prepares the individual to cope with emergency.
It prepares the individual for fight and fight.
when an animal or man is suddenly confronted to
danger (e.g. a car coming head on towards you or an
attacker confronting you),
he either fights or flights. For this he needs sympathetic
nervous system.
The ultimate effect is to allow the individual to run
faster, fight harder, think faster than normal for that
particular person.

53. sympathetic nervous stimulation causes….
dilatation of pupils to allow more light
increase more blood flow to vital organs
i.e. increase BP and CO
increase alertness
increase BMR
cutaneous vasoconstriction
This action of sympathetic nervous system called
“mass discharge”. This usually occurs in stressful
conditions. Also known as alarm / stress response.

54. Fight and flight reaction are sometimes
called as
Sympatho -adrenal system.
There are two parts in adrenal gland.
(1) adrenal cortex  steroids
(2) adrenal medulla  catecholamines

55. Structure of the medullaStructure of the medulla
adrenal medulla consists of hormone producing cells
called chromaffin cells (pheochromocytes) stained
brown with chrome salts, which surrounds blood
vessels.
Since they are controlled directly through
preganglionic fibres, hormones release can occur
very quickly.
80% epinephrine, 20% nor epinephrine.
Stored in granulated vesicles. In granules Ep and NE
bound to ATP and binding protein chromogranin.

56. Formation of catecholamines :-Formation of catecholamines :-
Phenylalanine (in diet)
↓ phenylalanine hydroxylase
(in liver)
tyrosine ( in diet)
↓ tyrosine hydroxylase
3,4 Dihydroxy phenylalanine (DOPA)
↓ DOPA decarboxylase
Dopamine
↓ Dopamine β hydroxylase
Nor epinephrine (NE)
↓ Phenylethanolamine N
↓ methyl transferase
↓ (PNMT)
↓
Epinephrine

57. Release of catecholamines
Preganglionic fibres in splanchnic nerves
↓
Release of Ach
↓
Stimulates chromaffin cells by promoting
entry of Ca++
↓
Release of catecholamines by exocytosis

58. Epinephrine Norepinephrine
Excites both α and β
receptors equally.
More dominant effect on
β2 receptors.
Mainly α receptors. No
affinity for β2 receptors.
weak vasoconstriction. powerful vasoconstriction.
Vasodilatation in blood
vessels in skeletal muscles
and liver (β2 receptor)
vasodilatation causes fall
in the peripheral resistance
Causes increase in
peripheral resistance and
arterial blood pressure.
BMR increases very high. BMR increases slightly.

59. Conditions in whichConditions in which ↑sed↑sed
catecholamine secretioncatecholamine secretion
1. physical exertion / emotional stress
2. exposure to cold
3. fall in arterial BP
4. Asphyxia
5. hypoglycemia

60. PHEOCHROMOCYTOMAPHEOCHROMOCYTOMA
Tumor of the chromaffin cells of the adrenal
medulla, called pheochromocytoma
↓
hypersecretion of the medullary hormones.
↓
rapid heart rate
Headache
high blood pressure
high levels of sugars in blood and urine
flushing of face
Nervousness
Sweating
decrease gastric motility

61. CONTROL OF ANS BY HIGHER CENTRESCONTROL OF ANS BY HIGHER CENTRES
Hypothalamus is the major control & integration center of the ANS.
Output from hypothalamus influences autonomic centres in the
medulla & spinal cord.
The posterior and lateral portions of the hypothalamus control
sympathetic division.
these area stimulated there is….
 increase in HR
 increase in force of contraction
 rise in blood pressure
 increase body temperature
 increase in rate and depth of respiration
 dilatation of pupil
 inhibition of the GIT
the anterior and medial portions of the hypothalamus control
parasympathetic.
Stimulation leads to opposite action.

62. HORNER’S SYNDROMEHORNER’S SYNDROME
Unopposed action of the PaNS supply to the pupil of
the eye can occur in Horner's Syndrome.
This condition arises when there is a lesion of the
cervical sympathetic ganglion supplying the eye
head and neck.
Features :-
constriction of the pupil on affected side
drooping of the eyelid
slight retraction of the eyeball within the orbit
loss of sweating on the affected side of the head and
neck
Persistent vasodilatation on face and head on the
affected side