The autonomic nervous system (ANS) controls visceral functions like cardiac muscle and smooth muscle of blood vessels. It has two divisions - the sympathetic and parasympathetic nervous systems. The sympathetic division prepares the body for "fight or flight" while the parasympathetic division conserves energy and promotes "rest and digest". Both work to maintain homeostasis through a balance of stimulation. The ANS uses a two-neuron chain and ganglia located outside the CNS. It is not under voluntary control.

2. Autonomic NervousAutonomic Nervous
SystemSystem
Dr Ayyaz AhmedDr Ayyaz Ahmed
AP PhysiologyAP Physiology

3. Learning ObjectivesLearning Objectives
• Outline the functions of ANS
• Describe the functions of
Sympathetic Nervous System

4. All smooth muscles
All Glandular structures Myocardium
General Visceral Efferent

5. ANSANS
Innervates all innervated
structures in the body except
NMJ of SKM

8. Autonomic nervousAutonomic nervous
system (ANS)system (ANS)
Part of nervous system that controls
visceral functions
• Cardiac muscle, smooth muscle (blood
vessels, GIT, urinary bladder etc) glands
(secretions)
Not under voluntary control

9. Anatomy of the Motor Output inAnatomy of the Motor Output in
Sympathetic and ParasympatheticSympathetic and Parasympathetic
nervesnerves

10. Autonomic nervous system
• Two neuron chain from CNS to effector
organ
• Pre and postganglionic neurons
Somatic nervous system
• Single neuron connects CNS with effector
organ

11. NeurotransmittersNeurotransmitters
involvedinvolved

12. Autonomic nervousAutonomic nervous
system (ANS)system (ANS)
Ganglion
• Cluster of neurons outside CNS
• Autonomic ganglion
oSite of synapse between autonomic pre &
post ganglionic fibers
oParavertebral ganglionic chain
oPrevertebral (collateral) ganglia

13. Autonomic nervousAutonomic nervous
system (ANS)system (ANS)
Cell body of preganlionic neuron
• Lies in CNS
oSpinal cord (sympathetic division)
oBrain and spinal cord (parasympathetic
division)
Cell body of postganglionic neuron
• Lies in autonomic ganglia

14. Autonomic nervousAutonomic nervous
system (ANS)system (ANS)
Sympathetic nervouss system
• Short preganlionic fibers
• Long postganglionic fibers
Parasympathetic nervous system
• Long preganlionic fibers
• Short postganglionic fibers

16. Autonomic nervousAutonomic nervous
system (ANS)system (ANS)
Cholinergic fibers
• Fibers releasing acetylcholine
Adrenergic fibers
• Fibers releasing noradrenalin

17. Autonomic nervousAutonomic nervous
system (ANS)system (ANS)
All preganlionic fibers are cholinergic
All postganglionic parasympathetic
fibers are cholinergic
Almost all postganglionic
sympathetic fibers are adrenergic
• postganglionic sympathetic fibers to
sweat glands and piloerector muscles
are cholinergic

18. Autonomic nervousAutonomic nervous
system (ANS)system (ANS)
Receptors
• Nicotinic receptors -in autonomic ganglia
• Muscarinic receptors -in effector organs
stimulated by postganglionic cholinergic
fibers
• Adrenergic receptors -in effector organs
stimulated by postganglionic adrenergic
fibers
oα adrenergic receptors (α1 and α2)
oΒ adrenergic receptors (β1 and β2)

19. Muscarinic receptors in the parasympathetic
system β M1 M3, M5 M2, M5
AcetylcholineAcetylcholine
Neuroscience, Sinauer Asssoc., Inc

20. Neuroscience, Sinauer Asssoc., Inc
Adrenergic receptors in the sympathetic system
Norepinephrine
β α1 α2
Norepinephrine

22. Autonomic nervousAutonomic nervous
system (ANS)system (ANS)
Sympathetic division
• Thoracolumbar (T1to L2)
Parasympathetic division
• Craniosacral (III, VII, IX, X cranial
nerves & S1to S4)

25. Sympathetic NS
NE, EPINEPHRINE
Stimulated Inhibited
All the tissues
α1 A.R
Except
Heart, JGA, Lipocytes
Β1 A.R
All the tissues
β2 A.R
Except
Presynaptic Nerve Endings
Platelets, some part of GIT
α2 AR

29. DP- Alpha 1 Receptors
Cilliaris- Beta 2 Receptors

30. Skin
Vessels Stimulated
Alpha 1 Receptors

32. Respiratory System
Blood Vessels
α1
Bronchial secretion Decreases
Mast Cells
β2
Bronchial Smooth
β2

36. Adrenal medulla
Stimulation of sympathetic innervation of
adrenal medulla causes release of large
quantities of epinephrine (80%) and
norepinephrine (20%)
Effect lasts 5-10 times longer
Sympathetic tone caused by basal
secretion from adrenal medulla
(.2 µg/kg/min Epinephrine and .05
µg/kg/min of noreepineohrine

37. Adrenal MedullaAdrenal Medulla
• Epinephrine affects
– more on beta
–Less on alpha
–More metabolic effect
• Adrenal medulla provides back
up for sympathetic function in
addition to normal channel of
sympathetic nerves

39. Thank You

40. Autonomic nervousAutonomic nervous
system (ANS)system (ANS)
Dual supply
• All the viscera supplied by both the
divisions of ANS
• Sympathovagal balance determines the
ultimate function of the viscera

41. Functions of ANSFunctions of ANS
Sympathetic and parasympathetic
components of ANS function to
maintain homeostasis at
subconscious level -maintain stable
internal environment

42. α1 receptors
•vascular smooth muscle, on GI and bladder sphincters
and radial muscle of the eye. causes excitation
(contraction)
α2 receptors
•presynaptic nerve terminals, platelets, fat cells, walls of
GI tract causes inhibition (relaxation, dilation)
β1 receptors
•SA node, AV node, ventricular muscle of heart
• produces excitation, increases heart rate, contractility,
and conduction velocity
β2 receptors
•vascular smooth muscle of skeletal muscle, bronchioles,
walls of GI tract and bladder
•produces relaxation: dilation of vascular smooth muscle
and relaxation of bladder, bronchioles
Location of specific adrenergic receptors

44. Co-Transmission
Acetylcholine and Norepinephrine play
important, but not exclusive, roles
in the autonomic nervous system

45. Sweat glandsSweat glands
• Sympathetic fires supply them. If
stimulated copious sweating
• Acetylcholine is neurotransmiiter
except palms and soles which are
adrenergic
• Overall control is parasympathetic via
hypothalamus so sweating could be
called parasympathetic function

46. Stimulus RateStimulus Rate
• Low frequency required to fully
activate ANS as compared to
Skeletal nervous system

47. Sympathetic and
parasympathetic tone”
Continual basal activity of the
sympathetic
and parasympathetic systems allows
either branch
of the ANS to increase or decrease its
activity
of a stimulated organ
If tone lost intrinsic compensation in
some time

48. Denervation
supersensitivity
Receptor up regulation?

49. Enteric Nervous
System
Gastrointestinal tract nervous system
Myenteric plexus
(auberbach’s)
Meissner’s plexus
(submucosal)The Enteric Nervous System can function
on its own but is most often controlled by the
sympathetic and parasympathetic systems
Contains more neurons than the spinal cord and uses
many different neurotransmitters and neuromodulator
approaching the complexity of the CNS

50. Autonomic Reflexes
cardiovascular reflexes
gastrointestinal reflexes
bladder emptying
sweating
blood glucose
concentration
sexual reflexes

51. Alarm or Stress response
Mass discharge of sympathetic system allows
the body to make maximal use of its resource
thereby enhancing its chances for survival
•pupilary dilation
•increase heart rate and strength of contracti
•increase blood pressure
•increase blood flow to active muscles
•increase rates of metabolism
•increased blood glucose concentration
•increased muscle strength
•increase mental activity

52. Exceptions of isolatedExceptions of isolated
Function inFunction in
SympatheicSympatheic
• SWEATING
• Muscle activiy in animals
• Local reflexes (skin heat)
• Many GIT reflexes

53. Parasympathetic System Usually CausesParasympathetic System Usually Causes
specific localized responsesspecific localized responses
Parasympathetic cardiovascular reflexes
usually
act only on the heart to control its rate of
beating
Examples:Examples:
timulation of secretion in mouth while not
ffecting stomach, although sometimes they occ
ogether
In Contrast……...

54. Hypothalamus is critical
for coordinating autonomic
output.
It projects to several
brainstem nuclei and
coordinates autonomic
function with feeding,
thermoreg.,water balance,
circadium rhythm, sex
drive, etc., and thus plays a
dominant role in
integrating higher cortical
areas and autonomic
function.panic attacks, emotional stress,
cognitive activity
Medullary, pontine and mesencephalicMedullary, pontine and mesencephalic
control of ANS and their supervision bycontrol of ANS and their supervision by
HYPOTHALAMUSHYPOTHALAMUS

55. Functions of ANSFunctions of ANS
Sympathetic nervous system
• Prepares and mobilizes the body in
emergency (fright, fear, pain, rage etc)
• Fight or flight reaction

56. Functions of ANSFunctions of ANS
Parasympathetic nervous system
• Conserves and stores energy -puts the
body in cool and calm state

57. Functions of ANSFunctions of ANS
Sympathetic Parasympathetic
Heart
↑ heart rate
↑ force of contraction
Heart
↓ heart rate
↓force of contraction
Blood vessels
Constriction
Blood vessels
No effect
Lungs
Bronchodilation
Lungs
Bronchoconstriction
GIT
↓ motility
Sphincter contraction
Decreased secretions
GIT
↑ motility
Sphincter relaxation
Increased secretions

58. Functions of ANSFunctions of ANS
Sympathetic Parasympathetic
Salivary glands
Stimulates secretion
Salivary glands
Stimulates secretion
Sweat glands
Copious secretion
Sweat glands
Sweating on palms only
Eye
Papillary dilation
Flattening of lens
Eye
Papillary constriction
Thickening of lens
Urinary bladder
Relaxation of bladder wall
Sphincter contraction
Urinary bladder
Contraction of bladder wall
Sphincter relaxation

59. Autonomic nervousAutonomic nervous
system (ANS)system (ANS)
Mass discharge of sympathetic
system
• Simultaneous discharge of all portions of
sympathetic nervous system as a unit
• Due to activation of hypothalamus as a
result of fright, fear or pain
• Also called alarm or stress response of
the body
• Prepares the body for ‘emergency’

60. Autonomic nervousAutonomic nervous
system (ANS)system (ANS)
 Mass discharge of sympathetic system
• Increased BP
• Increased blood flow to active muscles
• Less blood flow to skin and GIT
• Increased rate of cellular metabolism
• Increased glycogenolysis and lipolysis
• Increased muscle strength
• Increased mental activity
• Papillary dilation
• Increased respiratory rate

61. Autonomic nervousAutonomic nervous
system (ANS)system (ANS)
Sympathetic and parasympathetic
tone
• Basal rate of discharge
• Allows single division to adjust
stimulation level of an organ
oSympathetic tone to blood vessels

62. Thank You