1. Chapter 4: physiology
Autonomic Nervous System
Girmay F.

2. Out line presentation
1.
Introduction
2.
Division of ANS

Sympathetic nervous system

Parasympathetic nervous system.
3. Adrenal medulla
4. Neurotransmitters and Receptors in ANS
2

3. Introduction
The human internal environments is regulated in
large measure by the:
•
ANS
•
Endocrine glands and
N.B. Integrated activities of these two systems
3

4. 
The subdivision of the Peripheral NS that regulates body
activities independently (autonomously) and continuously
without conscious effort.

ANS innervate

Smooth muscle, Cardiac muscle

Glands (eg, sweat glands, salivary glands)
4

6. 6

7. 7

8. 8

9. 
mediates visceral reflex responses that are involuntary
and largely unconscious.

Although survival is possible without an ANS, the
ability to adapt to environmental stressors and other
challenges is severely compromised.
9

10. The ANS affects the following:

Heart rate, Respiration rate

Digestion, Salivation

Perspiration

Diameter of the pupils

Micturition (urination)

Sexual arousal
10

11. 
Basic difference ANS VS SNS

Somatic division:

operates under our conscious (voluntary) control.

Cell bodies of motor neurons reside in CNS

One motor neuron extends from the CNS to skeletal
muscle.

Axons are well myelinated, conduct impulses rapidly.
11

12. 
Autonomic system:

chains of two motor neurons

1st = preganglionic neuron (in brain or spinal cord)

2nd = ganglionic neuron (cell body in ganglion
outside CNS) .


Slower because lightly or unmyelinated.
functions are involuntary
12

13. 13

14. 14

15. 
Preganglionic neurons :



the first neuron and its cell bodies in CNS
Myelinated.
Postganglionic neurons:

The second neuron

its cell bodies in the autonomic ganglion

Unmyelinated
15

16. 
The nerve impulse transmitted from pre-to-post ganglion
occur via Acetyl choline (ACH).
N.B
1.
Ganglion: the collection of nerve cell bodies in the
peripheral nervous system.
2.
Nuclei : collection of nerve cell bodies in CNS.
16

17. 17

18. Divisions of Autonomic Nervous System

The ANS has two major divisions: the sympathetic and
parasympathetic nervous systems.

Sympathetic division (speeds up)
•
Prepares body for ‘fight or flight’ situations
Parasympathetic division (slows down)

•
Prepares body for ‘resting and digesting’ activities.
18

19. 19

20. 
some target organs are innervated by both divisions
(Dual innervation), Opposing effects on the same
organ.

others are controlled by only one.

It has also Enteric division and has role in digestive
tract.
20

21. Sympathetic nervous system
21

22. 
You come across a gangster with sharp materials @Gcmhs
campus at 8:00 pm on your walk to GCMHs library
………… what happens ???
1.
Heart rate
2.
Breathing rate
3.
Size of pupil
4.
Bronchiole smooth muscle
5.
Digestive system
6.
Skeletal system
7.
Cutaneous circulation
8.
Cerebral circulation
22

23. Sympathetic nervous system

mobilization & increased metabolism “fight, flight or
fright”.

Involves in activities of exercise, excitement,
emergency, and embarrassment.

Non-essential activities are dampened (GI/urinary).

Promotes adjustments during exercise – blood flow to
organs is reduced, flow to muscles is increased
23

24. 
Its activity is illustrated by a person who is threatened

HR increase and breathing is rapid and deep.

The skin is cold and sweaty, and the pupils dilate.

Bronchioles dilate which increasing
ventilation, delivering more oxygen to cells.
24

25. 
Constriction of visceral & cutaneous blood vessels
(blood is shunted to skeletal muscle ).

Liver releases more glucose into blood to provide
more readily avail energy

Targets adipocytes for lipolysis.
25

26. 
Basic organization

Issues from T1-L2 ( thoraco lumbar division )

Preganglionic fibers form the lateral gray horn.

Supplies visceral organs and structures of superficial body
regions.

Contains more ganglia than the parasympathetic division
26

27. Parasympathetic Division

Cranial outflow

Supplies the visceral structure in the head, neck and
face via the oculomotor, facial and glossophryngeal
nerves.


Thorax and upper abdomen via vagus nerves.
Sacral outflow

Supplies pelvic organ via the pelvic branches of the
second to fourth sacral spinal nerves.
27

28. 
Cranial Outflow
Preganglionic fibers run via:



Facial nerve (VII)

Glossopharyngeal nerve (IX)


Oculomotor nerve (III)
Vagus nerve (X)
Cell bodies located in cranial nerve nuclei in the brain
stem.
28

29. 
oculomotor nerve

ciliary ganglion

Ciliary muscle, accommodation for near vision

Pupillary constrictor of iris(sphincter), miosis
(contraction of pupil).
29

30. 
Facial nerve

Submandibular and sublingual glands via
Submandibular ganglion




Lacrimal gland via Pterygopalatine ganglion .
Glands of nasal cavity, mouth, and palate
Glossopharyngeal nerve
Parotid gland via otic ganglion
30

31. 
Outflow via the Vagus Nerve (X)

Fibers innervate visceral organs of the thorax and most of the
abdomen.

Stimulates - digestion, reduction in heart rate and blood pressure.

Preganglionic cell bodies


Located in dorsal motor nucleus in the medulla.
Ganglionic neurons

Confined within the walls of organs being innervated.
31

32. 
Sacral Outflow

Emerges from S2-S4

Innervates organs of the pelvis and lower abdomen

Preganglionic cell bodies


Located in visceral motor region of spinal gray matter.
Form pelvic splanchnic nerves.
32

33. 33

34. SNS VS PNS

Sympathetic
1. Thoracolumbar

Parasympathetic
1. Craniosacral
2. Short preganglionic and long 2. Long preganglionic and short
post ganglionic neurons.
3. Sympathetic axons – highly
branched , Influences many
organs
4. Location of Ganglia: Close to
postganglionic fibers
3. Parasympathetic axons – few
branches , Localized effect.
4. Location of ganglia: In the
visceral effector organs
the spinal cord
34

35. SNS VS PNS cont’d…

Neurotransmitter released by preganglionic axons


Acetylcholine for both branches (cholinergic)
Neurotransmitter released by postganglionic axons

Sympathetic – most release norepinephrine (adrenergic).

Parasympathetic – release acetylcholine .
35

36. 36

37. 37

39. 39

40. Adrenal medulla

Major organ of the sympathetic nervous system.

Secretes great quantities epinephrine (a little
norepinephrine)

Stimulated to secrete by preganglionic sympathetic
fibers.
40

41. 41

42. 42

43. Neurotransmitters & Receptors in ANS
1. Neurotransmitter

chemical messengers produced by the cell bodies of
neuron and have role in communication between neurons
and neuron, muscle coordination.

Neurotransmitters are released by the presynaptic cell.
43

44. 
Bind to specific receptors in the postsynaptic cell
membrane.

Binding has either an excitatory or an inhibitory effect on
the effector, depending on the specific receptor.

Acethylcholine(ACh) and Norepinephrine( NE) are the
major neurotransmitters in autonomic nervous system.
44

45. A.
Both the preganglionic and postganglionic axons in the
parasympathetic division release acetylcholine and thus
are called Cholinergic.
B.
The preganglionic axon and a few postganglionic axons
in the sympathetic division are also cholinergic(blood
vessels of skeletal muscle and sweat gland).
45

46. C. Most of the postganglionic axons of the sympathetic
division release Norepinephrine and are called
Adrenergic.
D. The postganglionic chromaffin cells at the adrenal
medulla secrete Adrenaline(epinephrine).
46

47. 
Acetylcholine


ALL parasympathetic postganglionic neurons


ALL preganglionic neurons
Blood vessels of muscle and sweat gland.
ACH is rapidly hydrolyzed by a membrane-associated
Acetylcholinesterase in the synaptic cleft.

Effects are short and localized.
47

48. 48

49. 
Norepinephrine (= Noradrenalin):

Most sympathetic postganglionic neurons

Exceptions: Sweat glands (Acetylcholine), Renal
arteries (Dopamine).

Epinephrine (= Adrenaline):
– Adrenal medulla upon sympathetic impulses
49

50. 50

51. 2. Receptors
A. Cholinergic Receptors:

Receptor for Ach.

classified as nicotinic, muscarinic.

Muscarinic (M): at the target organ named after activation
by Muscarine (poison of Amanita muscaria).
51

52. 
Hetrotrimeric G protein-coupled

CNS, gastric mucosa: M1

Cardiac: M2


Glandular/Smooth muscle: M3
The effect of ACh binding:

Can be either inhibitory or excitatory.

Depends on the receptor type of the target organ
52

53. Nicotinic (N) receptors

All ganglionic neurons of both sympathetic and
parasympathetic

At the neuromuscular junction

The hormone-producing cells of the adrenal medulla

The effect of ACh binding to nicotinic receptors is always
stimulatory

named after activation by Nicotine.
53

54. 
The effect of ACh binding to nicotinic receptors is
always stimulatory (excitatory ).

Stimulation of muscarinic receptors produces a longer
lasting effect than does stimulation of nicotinic
receptors.

The effects produced by the PS division center on
relaxation, food processing and energy absorption.
54

55. 55

56. B. Adrenergic receptors: respond to norepinephrine/epinephrine

Subdivided in to α and β.

α Adrenergic receptors

α receptors are located postsynaptically at sympathetic
neuroeffector junctions of many organs.

In general, alpha receptors mediate excitation or increased
activity of the effector cells.

Vascular smooth muscle is an important site of alpha
receptors.
56

57. 
They are subdivided into two types:

1

Located in the vascular smooth muscle of the skin and
splanchnic regions, the gastro intestinal(GI) and bladder
sphincters, and the radial muscle of the iris.

Produce excitation( e. g. contraction or constriction).
57

58. 
2

Are located in presynaptic nerve
terminals, platelets, fat cells and pancreatic islets.

Effects

platelet aggregation

Vasoconstriction

inhibition of norepinephrine release and of insulin
secretion.

Often produce inhibition ( e. g. relaxation or
dilation).
58

59. 59

60. 
β adrenergic receptors

are also located postsynaptically at sympathetic
neuroeffector junctions of many organs.

In general, beta receptors mediate relaxation or
Decreased activity of the effector cells. Thus, Blood
vessels dilate and Uterine smooth muscle relaxes in
response to activation of beta receptors.
60

61. 
A notable exception – NE binding to  receptors of the heart
is stimulatory.

There are three known types of beta receptor, designated
β1, β2 and β3.

β1-Adrenergic receptors : are located mainly in the heart.

Produce excitation ( e. g. increased HR, increased
conduction velocity, increased contractility).
61

62. 
β2-Adrenergic receptors: are located on the vascular
smooth muscle of skeletal muscle, bronchial smooth
muscle, and in the wall of GI tracts and bladder.

Produce relaxation( e.g. dilation of vascular smooth
muscle, dilation of bronchioles, relaxation of the bladder
wall.

β3- adrenergic Receptors are located in fat cells.
62

63. 63

64. Rhythm disturbances are a major concern with drugs that activate the beta1 receptor.
64

65. 65

66. 
Alpha receptor activation leads to smooth muscle
contraction

Activation of beta 1 leads to smooth muscle
contraction(especially in heart).

Activation of beta 2 receptors lead to smooth muscle
relaxation.
66

67. 67

68. Dual Innervation

Most
of viscera receive nerve fibers
from both
parasympathetic and sympathetic divisions.

Both divisions do not normally innervate an organ equally.

Antagonistic effects

oppose each other
68

69. 
Exerted through dual innervation of same effector



Heart rate decreases (parasympathetic)
Heart rate increases (sympathetic)
Exerted because each division innervates different cells

pupillary dilator muscle (sympathetic) dilates pupil

constrictor pupillae (parasympathetic) constricts pupil
69

71. 
Cooperative effects seen when 2 divisions act on different
effectors to produce a unified effect



parasympathetics increase salivary serous cell secretion
sympathetics increase salivary mucous cell secretion
ANS cooperation is best seen in control of the external
genitalia
71

72. 
Parasympathetic
fibers
cause
vasodilation
and
are
responsible for erection of the penis and clitoris.

Sympathetic fibers cause ejaculation of semen in males and
reflex peristalsis in females

Some effectors receive only sympathetic

adrenal medulla, arrector pili muscles, sweat glands and
many blood vessels.
72

73. Summary
Effector Organ
Nicotinic
receptor
α,β1 β2
receptors
Sympathetic
Preganglionic
Postganglionic
ACh
Noradrenaline
Effector Organ
Nicotinic
receptor
Muscarinic
receptors
Parasympathetic
Preganglionic
Postganglionic
ACh
ACh
73

74. Summary Cont.
Nicotinic
receptor
Adrenalin (80%)
Noradrenalin (20%)
ACh
Adrenal gland
Skeletal
muscle
Somatic
ACh
Nicotinic
receptor
74

75. Receptor
Location
Response
α1
Widespread, found in most
tissues
Excitation, stimulation
of metabolism
α2
Sympathetic neuroeffector
junctions
Parasympathetic neuroeffector
Junctions
Inhibition of effector cell
Heart, kidneys, liver, adipose
tissue*
Stimulation, increased energy
consumption
Adrenergic
Receptors
β1
β2
Cholinergic
Receptors
Nicotinic
Muscarinic
Smooth muscle in vessels of
heart and skeletal muscle;
smooth muscle layers in the
intestines, lungs, and bronchi
Inhibition of neurotransmitter
release
Inhibition, relaxation
All autonomic synapses between
preganglionic and ganglionic
neurons; neuromuscular
junctions of the SNS
Stimulation, excitation;
muscular contraction
All parasympathetic
neuroeffector
junctions; cholinergic
sympathetic
neuroeffector junctions
Variable
Adrenergic and Cholinergic Receptors of the ANS
75

76. Recall

Describe the main functions of ANS.

Distinguish the division of the ANS

Appreciate the difference between the sympathetic
nervous and parasympathetic nervous system.

Identify the neurotransmitters and its receptors in ANS.
76