This document discusses the autonomic nervous system and adrenal medulla. It begins by describing the peripheral nerves, including the 12 cranial nerves and 31 spinal nerves. It then discusses the autonomic nervous system in more detail, including its role in involuntary functions. It describes the sympathetic and parasympathetic nervous systems, their origins, neurotransmitters, and effects on various organs. The adrenal medulla is discussed as modified neurons that secrete epinephrine and norepinephrine in response to sympathetic stimulation. Dual innervation of organs by the sympathetic and parasympathetic systems allows for homeostatic balance.

1. Chapter 5
Autonomic Nervous System
and
Adrenal Medulla
By
Dr mohamed Majidho (Lecturer)
Global science Univeristy
Collage of health science
Physiology Unit
Dr M Majidho

2. Dr M Majidho
Peripheral Nerves
• 12 pairs of cranial nerves
– Afferent (sensory)
• CN-I: Olfactory- sense of smell
• CN-II: Optic– sense of vision
• CN-VIII: Vestibulochoclear- sense of equilibrium & hearing
– Mixed nerves(sensory and motor)
• CN-IV: Trochlear, CN- V: Trigeminal, CN-VI: Abduscens, CN-
VII: Facial, CN-IX: Glossopharyngeal, CN-X: Vagus
– Efferent (Motor)
• Occulomotor- motor to intrinsic & extrinsic muscles of eyes
• Accessory- motor to soft palate, pharynx & larynx and neck
• Hypoglossal- motor to muscle of the tongue

3. Dr M Majidho

4. Dr M Majidho
• 31 pairs of spinal nerves
– All contain afferent and efferent
• 8 cervical
• 12 thoracic
• 5 lumbar
• 5 sacral
• 1 coccygeal
• Peripheral nerve consist 12 pairs of cranial nerve &
31 pairs of spinal nerve.
• Autonomic NS is part of this peripheral nerve.
• Out of 12 cranial nerves only III, VII, IX & X belongs to autonomic.
• Among spinal nerves autonomic arise from thoracic, lumbar & sacral

5. Dr M Majidho
• .

6. Dr M Majidho
• Autonomic Nervous System
– Subdivision of the peripheral nervous system
– It innervate involuntary organs, smooth muscle, glands
– Regulates body activities not under conscious control
– Can effectively control may activities at a time
– Controls most visceral body function
– Thus helps to control
arterial pressure  blood chemistry
 respiration  immune response
 circulation  gastrointestinal motility,
 gastrointestinal secretion,  urinary bladder emptying,
 Defecation, sweating, body temperature & many other.

7. Dr M Majidho
• ANS bring rapid & intense change in visceral functions.
– With in 3-5 seconds it doubles the heart rate
– With in 10-15 sec it doubles the Arterial BP
• Autonomic motor use 2 neurons in efferent pathway
(between CNS & target organ).
– Preganglionic neurons and
– postganglionic neurons
• Ganglia is group of cell bodies out side CNS
• It innervates non-skeletal (non-somatic) muscles
– Cardiac muscle (the heart)
– Smooth muscle (walls of viscera and blood vessels)
– Internal organs -Skin

8. Dr M Majidho
• .

9. Dr M Majidho
• Comparison b/n somatic (Voluntary) and autonomic motor neuron.
Feature Somatic Motor Autonomic Motor
Effector organs Skeletal muscles Cardiac & smooth muscle, glands, visceral organ
Presence of
ganglia
No ganglia Cell bodies of postganglionic autonomic fibers
located in paravertebral(lateral), prevertebral
(collateral), and terminal ganglia
# of neurons One Two from CNS to effector.
Type of
neuromuscular
junction
Specialized motor
end plate
No specialization of postsynaptic membrane; all
areas of smooth muscle cells contain receptor
proteins for neurotransmitters
Effect on muscle Excitatory only Either excitatory or inhibitory
Type of nerve
fibers
Fast-conducting,
thick (9–13 μm),
and myelinated
Slow-conducting; preganglionic fibers lightly
myelinated but thin (3 μm); postganglionic
fibers unmyelinated & very thin (≈ 1.0 μm)
Effect of
denervation
Flaccid paralysis
and atrophy
Muscle tone and function persist; target cells
show denervation hypersensitivity

10. Dr M Majidho
Autonomic & Somatic Motor Systems

11. Dr M Majidho
Autonomic Ganglia
It is collections of neurons cell bodies outside CNS
Contains cell body of postganglionic neurons & axon
terminal of preganglionic neurons.
They are divergence centers and distribution centers to
various organs.

12. Dr M Majidho
Types of Autonomic ganglia
• a. Lateral (paravertebral) ganglia of SNS
– i. Forms 23 pairs of sympathetic chains
– ii. Each lies on either side of vertebral column as
• 3 cervical, 12 thoracic, 4 lumbar, 4 sacral
• b. Collateral (Prevertebral) ganglia of SNS
– i. Found midway between spinal cord & viscera
– ii. Located along sympathetic pathway as
• Celiac ganglia.
• Superior mesenteric ganglia
• Inferior mesenteric ganglia.
• c. Terminal ganglia of PSNS
– i. Found near or with in the autonomic effect organ
To
heart, lungs, blood vessel
Salivary gland, eye, skin
To
GIT, pancreas, splanchnic blood Vessel,
Kidney, spleen, adrenal glands, Bladder,
genital organs

13. Dr M Majidho
• .
ANS - solid lines (preganglionic fibers)
-dashed lines (postganglionic fibers).

14. Dr M Majidho
• Though involuntary ANS is under control of centers
• spinal cord,
• brain stem,
• hypothalamus
• cerebral cortex (limbic cortex)
• ANS consists:
– sympathetic nervous system,
– parasympathetic nervous system and
– Enteric nervous system

15. Dr M Majidho
• Autonomic control areas in brain stem & hypothalamus.

16. Dr M Majidho
Enteric nervous system
– A unique neural system embedded in an unlikely place
(in the gut wall)
• In lining of esophagus, stomach, intestine, pancreas,
gall bladder
– Exist as nerve plexuses (net work)
• an outer plexus- myenteric plexus or Auerbach’s plexus,
• an inner plexus- submucosal plexus or Meissner’s plexus
– Has connection with sympathetic & parasympathetic

17. Dr M Majidho
Enteric nervous system
– Contain as many number of neurons as in spinal cord
– Considered as little brain because it can operate with
great deal of independence
– Enteric sensory neurons monitor
• Tension, stretch of GIT walls, chemical status, and
hormone level in the blood
– This information is used to govern motility, mucus
secretion, hydro-electrolyte secretion, blood flow of GIT.

18. Dr M Majidho
Sympathetic Nervous System
• The sympathetic nerve fibers
– Originate from gray mater of lateral horn in spinal cord
b/n T-1 & L-2 to corresponding spinal nerves.
– First pass into the sympathetic chain ganglia
– Then to the target tissues and organs they innervate.
• Thus sympathetic neuron originate from thoracolumbar
region of spinal cord.
• Sympathetic has:
– (1) two paravertebral chains of sympathetic ganglia
– (2) two prevertebral ganglia (celiac & hypogastric) and
– (3) nerves extending from ganglia to different organs.

19. Dr M Majidho
• The sympathetic chain of ganglia extends from cervical to coccygeal levels of the
spinal cord to activate postganglionic neurons that innervate all body segments .

20. Dr M Majidho
• Sympathetic use neurotransmitter acetylcholine (Ach) at ganglia and
norepinephrine (NE) at the target organ.
– Exception:-Use Ach at sweat gland, piloerector muscle, skeletalM. blood vessels
• Ach or Ach-like substances applied to the ganglia, will excite
postganglionic neurons.
• Sympathetic axons are highly branched to influences many organs

21. Dr M Majidho
• Sympathetic has short preganglionic & long postganglionic.
– Preganglionic fibers from gray lateral horn
– Contains more ganglia than the parasympathetic division
– Supplies visceral organs & other effectors

22. Dr M Majidho
• .
ANS - solid lines (preganglionic fibers)
-dashed lines (postganglionic fibers).

23. Dr M Majidho
• Divergence when preganglionic fibers branch to
synapse with numerous postganglionic neurons
located in ganglia.
• Convergence when a postganglionic neuron
receives synaptic input from many preganglionic.
• The divergence & convergence of impulses in
ganglia results in mass activation- thus sympathetic
activate all of its effectors at the same time.

24. Dr M Majidho
• The distribution of sympathetic nerves to each organ is
determined partly by the location of embryonic origin.
– Eg.1 Heart receives most sympathetic nerve fibers from
the neck portion of sympathetic chain
• because heart is originated from the neck of embryo &
translocated into thorax.
– Eg. 2 Abdominal organs receive most of sympathetic
innervation from the lower thoracic spinal cord segments
as primitive gut originated in this area.
• .

25. Dr M Majidho
• Effects of Sympathetic
– "Fight or Flight" Branch of the ANS
• Used in emergency situations
– where body needs a sudden burst of energy,
– Increase energy production and expenditure
– By increasing energy producing reactions
• It is essential for any stressful situation

26. Dr M Majidho
• Thus sympathetic system:-
–  cardiac output by raising heart rate & contractility via β-1
– pulmonary ventilation by  breathing rate & bronchodilation
(beta-2)
–  blood glucose level by glycolysis via beta-2
– Free fatty acid level by lipolysis from adipose tissue via β-3
– By constricting arterioles shift (routes) blood flow from GIT, skin,
inactive muscle to active muscles.
– Pupil dilation (by contracting radial/meridian/ smooth M. in iris)
• Slows down digestion, GIT secretion, kidney filtration, defication,
urination, sexual stimualtion &other functions not needed during
emergencies.
• Sweating (cold sweat due to contraction in skin), dry mouth by
saliva secretion, & piloerection.

27. Dr M Majidho
• Sympathetic responds by Mass Discharge
– During fright, fear, rage or severe pain.
– When large portions of sympathetic discharge at a time
– Known as Alarm” or “Stress” Response
– Results widespread reaction throughout body
• Thus :
• 1.  arterial pressure
• 2.  blood flow to active muscles -
 flow to GIT, some organs, skin, inactive muscle
• 3.  rates of cellular metabolism throughout the body
• 4.  glycolysis in the liver and in muscle
• 5.  blood glucose level 6.  muscle strength
• 7.  mental activity 8.  rate of blood coagulation

28. • Thnk you
Dr M Majidho

29. Dr M Majidho
• Adrenal Medullae
• Adrenal medullae is endocrine gland at the core of adrenal gland on
top of each kidney.
• Preganglionic sympathetic nerve directly supply the two adrenal
medullae with out synapsing in ganglia.
• It contain modified neuronal cells that secrete epinephrine (80%) &
norepinephrine (20%) into the blood stream.
• These secretory cells are embryologically derived from nervous tissue
& act as postganglionic neurons.
• It bring effect of sympathetic nervous system.

30. Dr M Majidho
• The adrenal medulla is considered as sympathetic
ganglion where postganglionic neurons have lost
their axons and become secretory cells.
• The cells secrete when stimulated by sympathetic
preganglionic nerve fibers via splanchnic nerves.
• Adrenal medullary hormones are essential during
emergencies like sympathetic nerve .

31. Dr M Majidho
• Special sympathetic supply to adrenal medullae

32. Dr M Majidho
• Parasympathetic Nervous System
• Originate from cranial and sacral region (Craniosacral).
• It has long preganglionic nerve that synapse near or in the
target organ & very short postganglionic nerve.
– except few cranial parasympathetic nerves
• It use neurotransmitter acetylcholine (Ach) both at ganglia
& target organ.
• Parasympathetic fibers leave CNS via cranial nerves III,
VII, IX, & X; also from sacral S2 –S3 & rarely S1 & S4.

33. Dr M Majidho
• About 75 % of all parasympathetic nerve fibers are vagus
nerves (cranial nerve- X), passing to the entire thoracic and
abdominal regions of the body.
• Thus vagus nerves supply;
– heart, lungs, esophagus, stomach, entire small intestine,liver,
gallbladder, pancreas, kidneys, proximal half of the colon and
upper portions of the ureters..
• Cranial nerve-III :- to pupil sphincter (circular SM in iris) & ciliary
muscle (for lens curvature or accommodation/focusing/)
• Cranial nerve-VII:- to lacrimal, nasal,submandibular
• Cranial nerve-IX:- to parotid gland.

34. Dr M Majidho
• .
Deem light
Normal light
Bright light
Oculomotor

35. Dr M Majidho
ANS for accommodation
• Parasympathetic contract ciliary muscle lens become rounded for near
sight.
• Sympathetic relax ciliary muscle using beta-2, lens become thin (flat)
for far vision. Power of lens decrease

36. Dr M Majidho
• The Parasympathetic Division.

37. Dr M Majidho
• Sacral fibers(S-2 & S-3) in pelvic nerve supply:-
– descending colon,rectum, urinary bladder,
– lower portions of the ureters
– external genitalia to cause erection.
Effects of parasympathetic
• It is referred as “Rest & Digest”.
• Used when the environment is stable & controlled.
• To conserve energy by reducing energy expending reaction.
• Also help to release energy from food by enhancing GIT activity.
Cranial outflow
• III - pupils constrict
• VII - tears, nasal mucus, saliva
• IX (glossopharengeal) - parotid salivary gland
• X (Vagus) - visceral organs of thorax & abdomen.

38. Dr M Majidho
Effects of Parasympathetic
Vagus nerve (X)
Heart: inhibits contractility, rhythmicity (SA-node),
conductivity in atria
Bronchi and bronchioles: bronchoconstriction and
mucous secretion from bronchial glands
• Increase pulmonary vascular compliance through NO
mechanism. This is important at high altitude
Hepatobilary system- Secretion and release

39. Dr M Majidho
• PSNS on Gastrointestinal system:
• Increase motor activity of GIT wall & secretion of glands,
while inhibitory to the sphincters
• Distal colon, rectum and anal canal: defecation
• Pancreas: increase acinar and islets secretions
 Blood vessels: vasodilatation of arterioles except where there is
poor innervations as in renal and visceral arterioles plus the whole
veins
 Urinary bladder:
• Motor to detrusor and inhibitory to the sphincters (Micturition)
• Ureters: increases motility and tone
• .

40. Dr M Majidho
 Genital organs:
• Erection a hydraulic process triggered and sustained
by PSNS.
• PSNS activity gets it going and keeps it going.
• But orchestrated shift to SNS is necessary to stop it.
• The attendant of anxiety and worry, SNS, inhibit
erection and promote ejaculation
• Impotence and premature ejaculation is the complaint
of over stressed boy.

41. Dr M Majidho
• Sympathetic & parasympathetic
– have excitatory effects in some organs but inhibitory
effects in others.
• If sympathetic excite particular organ, parasympathetic
some time inhibits it.
– thus two systems occasionally act reciprocally.
• But most organs are dominantly controlled by sympathetic
or parasympathetic.

42. Dr M Majidho
• .

43. Dr M Majidho
• Dual Innervations with SNS & PSNS
• Homeostatic ability (internal balance) depend on this dual
innervations (balance b/n SNS & PSNS)
• Antagonistic dual innervations
– Eg. In heart –SNS  heart rate, contractility
–PSNS heart rate, contractility, conduction
• Complementary Dual Innervations
– Eg. Digestion. PSNS  enzyme, saliva, mucus secretion
SNS  secretion rate & concentrate secretion
• Cooperative dual innervations
– Eg. Coitus where PSNS bring arousal (erection)
SNS bring orgasm (ejaculation),

44. Dr M Majidho
• Autonomic Reflexes
• Many visceral functions are regulated by autonomic reflexes.
• Gastrointestinal Autonomic Reflexes.
• 1.Food in mouth initiates signal to salivatory nuclei of brain stem.
– Motor signal (reflex) via parasympathetic nerves to secretory
glands in mouth and stomach, causing secretion of digestive juices
• 2. As fecal matter fills rectum, sensory signal from stretched rectum
sent to sacral portion of spinal cord.
– reflex signal transmitted back to rectum & distal colon via sacral
parasympathetics to bring defecation (defecation reflex).
• Micturation Reflexes (urination) is controlled in the same way as
defecation.
• Cardiovascular Autonomic Reflexes- help to control arterial blood
pressure & the heart rate (baroreceptor reflex).

45. Dr M Majidho
• Sympathetic and Parasympathetic “Tone”
• Continues basal rates of sympathetic &
parasympathetic activity are known as sympathetic
tone & parasympathetic tone respectively.
• Tone allows a single nervous system increase and
decrease activity of stimulated organ.
– -eg. Sympathetic tone to arterioles
• .

46. Dr M Majidho
ANS neurotransmitters
• The neurotransmitter in ANS are:-
– Acetylcholine (Ach) from cholinergic neuron or
– norepinephrine (NE) from adrenergic neruon
• Ach is parasympathetic transmitter.
• NE is sympathetic transmitter.

47. Dr M Majidho
• Transmitters and Receptors.

48. Dr M Majidho
Synthesis & Release of Neurotransmitter
• Parasympathetic & sympathetic nerve fibers have bulbous
enlargements called varicosities.
• Transmitter vesicles of Ach & NE are synthesized & stored
in these varicosities.
• Varicosities also contain many mitochondria that supply
ATP to energize Ach & NE synthesis.
• Depolarization of action potential arrival at axon terminal or
varicosities  influx of Ca++ to stimulate transmitter
release by exocytosis.

49. Steps in Neurotransmission
Dr M Majidho

50. Dr M Majidho
• Steps of chemical synapse transmission.

51. Dr M Majidho
Synthesis, Destruction, & Duration of Ach Action.
• Ach is synthesized at axon terminal & varicosities of
cholinergic nerve fibers then stored in vesicles at high
concentration.
Acetyl-CoA + Choline Choline-Acetyl transferase  Acetylcholine
• Once released Ach persists in synaptic cleft for few seconds
to perform nerve signal transmission function.
• Then Ach split into an acetate ion & choline by means of
enzyme acetylcholinesterase (AchE).
• The choline formed here is taken back into nerve ending, to
be used again & again for Ach synthesis.

52. Dr M Majidho
• Synthesis of Norepinephrine
• Norepinephrine synthesis begins in axoplasm of adrenergic nerve &
completed inside secretary vesicles.
• The basic steps are the following:
1.Tyrosine Hydroxilation  Dopa
2. Dopa Decarboxylation  Dopamine
3. Transport of dopamine into vesicles
4. Dopamine Hydroxilation  Norepinephrine
one more step in adrenal medulla
5. Norepinephrine Methylation  Epinephrine(80%)

53. Dr M Majidho

54. Dr M Majidho
• .

55. Dr M Majidho
• Removal of Norepinphrine, & Its Duration of Action.
• After release by nerve endings it is removed from secretory
site in 3 ways:
– (1) Reuptake into adrenergic nerve endings by active
transport (50% to 80%).
– (2) Diffusion into the surrounding body fluids and then
into blood.
– (3) Destruction by tissue enzymes (monoamine oxidase
& catechol-O-methyl transferase ).

56. Dr M Majidho
• Cocaine blocks the reuptake of dopamine and norepinephrine into
the presnaptic axon terminals.
• This causes excess of these neurotransmitters to remain in synaptic
cleft & stimulate their target cells.
• Cocaine is a sympathomimetic drug (promotes effect of sympathetic )
by action of norepinephrine.
• This can result
– vasoconstriction of coronary arteries,
– leading to heart damage
• (myocardial ischemia,
• myocardial infarction, and
• left ventricular hypertrophy).
• The combination of cocaine with alcohol is more deadly and
common cause of death from drug abuse.

57. Acetylcholine receptors
Nicotinic receptors
 They are ligand-gated ion channels and fall into three
main classes:
Ganglionic (NN),
Muscle (NM) and
CNS subtypes
 Mediate fast excitatory synaptic transmission at neuromuscular
junction, autonomic ganglia, adrenal medulla and in the CNS
Muscarinic receptors
 Are G-protein coupled receptors found on tissues
innervated by postganglionic parasympathetic
neurons and on sweat glands
57
12/18/2023

58. M1 receptors ('neural')
Mainly located on membrane of nerve cells
 Both CNS & peripheral neurons
They mediate excitatory effects
Richly expressed in brain areas involved in cognition
 Deficiency of ACh-M1 mediated effect in the brain is possibly
associated with dementia
58
12/18/2023

59. M2 receptors ('cardiac')
 Found in the heart & presynaptic terminals of peripheral and central
neurons
 Inhibitory effects
M3 receptors ('glandular/smooth muscle')
 Location: glands, smooth muscle, endothelium
 Produce mainly excitatory effects
59
12/18/2023

60. M4 and M5
 Found in the CNS
All m Ach Receptors are activated by acetylcholine and blocked by
atropine
60
12/18/2023

61. • thank you
Dr M Majidho