1. The Autonomic Nervous System

2. Basic Setup of the Nervous System

3. Basic Setup of the Nervous System

4. What does the ANS do?
Certain fairly slow, bodily functions are so routine, we can have them operate without conscious control
Occasionally, things happen that require instantaneous diversion of energy
Stop doing the routine and shift resources into escape.
Hurry Up and Wait Things

7. How does the ANS work? The ANS consists of motor neurons that:
Innervate smooth and cardiac muscle and glands
Operate via subconscious control
Have viscera as most of their effectors

8. Comparison of Somatic and Autonomic Systems
Motor
Comparison of Somatic and Autonomic Systems
Somatic:
Control of skeletal muscles
Autonomic:
Regulates smooth muscle, cardiac muscle and glands

9. ANS Versus Somatic Nervous System (SNS)
The ANS differs from the SNS in the following three areas
Effectors
Who
Efferent pathways
How are the neurons arranged
Target organ responses
What: excitatory or inhibitory

10. Effectors
SNS
Skeletal muscles
ANS
Cardiac muscle
Smooth muscle
Glands

11. Efferent Pathways SNS ANS
Heavily myelinated axons of the somatic motor neurons extend from the CNS to the effector
ANS
Axons of the ANS are a two-neuron chain
The preganglionic (first) neuron has a lightly myelinated axon
The ganglionic (second) neuron extends to an effector organ

12. Target Organ Response SNS ANS
All somatic motor neurons release Acetylcholine (ACh), which has an excitatory effect
ANS
Preganglionic fibers release ACh
Postganglionic fibers release norepinephrine or ACh and the effect is either stimulatory or inhibitory
ANS effect on the target organ is dependent upon the neurotransmitter released and the receptor type of the effector

13. Review: Somatic vs. Autonomic efferent neurons
Voluntary Involuntary
Effectors: Skeletal M Effectors: Cardiac M.
Smooth M
Glands
Neurons extend from CNS to effectors without synapsing.
Two neurons to get from CNS to effectors; therefore one synapse.
"Two neuron chain"

14. Comparison of Somatic and Autonomic Systems

15. Comparison of Somatic and Autonomic Systems
Things this figure points out:
Myelination
One- vs. two-neuron chain
Length of pre- and post-ganglionic neurons
Effector organs
Neurotransmitters

16. Adrenal Glands

17. Divisions of the ANS
The two divisions of the ANS are the sympathetic and parasympathetic
Basically, the sympathetic mobilizes the body during extreme situations.
Basically, the parasympathetic performs maintenance activities and conserves body energy
The two divisions counterbalance each other’s activity (for the most part).
Parasympathetic: Rest and Digest
Sympathetic: Fight or Flight

18. Role of the Parasympathetic Division
Concerned with keeping body energy use low
Involves the D activities – digestion, defecation, and diuresis
Its activity is illustrated in a person who relaxes after a meal (Thanksgiving)

19. Role of the Parasympathetic Division
Blood pressure is low
Heart rate is low
Respiratory rates are low
Gastrointestinal tract activity is high
The skin is warm because the blood is in the skin
The pupils are constricted

20. Role of the Sympathetic Division
The sympathetic division is the “fight-or-flight” system (Big Dog)
Involves E activities – exercise, excitement, emergency, and embarrassment

21. Role of the Sympathetic Division
Promotes adjustments during exercise –
blood flow to organs is reduced,
flow to muscles is increased
Its activity is illustrated by a person who is threatened
Heart rate increases
Breathing is rapid and deep
The skin is cold and sweaty: the blood is in the muscles, not in the skin.
The pupils dilate: “to better see you with”

22. Anatomy of ANS: Sympathetic vs. Parasympathetic
There are two main differences in the anatomy of the sympathetic and parasympathetic systems.
Where the ganglia (or second synapses) are.
Where they exit the spinal cord

23. Location of Ganglia
Parasympathetic Ganglia (synapses) are on the target organ
Sympathetic Ganglia (synapses) are near the spinal cord

24. Anatomy of ANS
Para-sympathetic exits either in: a. cranial nerves b. sacrally
Sympathetic exits from T1- L2

25. Parasympathetic Division Outflow
Cranial Outflow
Cranial Nerve
Ganglion
Effector Organ(s)
Occulomotor (III)
Ciliary
Constricts iris
Facial (VII)
Pterygopalatin Submandibular
Salivary, nasal, and lacrimal glands
Glossopharyngeal (IX)
Otic
Parotid salivary glands
Vagus (X)
Located within the walls of target organs
Heart, lungs, and most visceral organs
Sacral Outflow
S2-S4
Located within the walls of the target organs
Large intestine, urinary bladder, ureters, and reproductive organs

26. Sympathetic Outflow Nerves Sympathetic Chain Ganglia
Cardiac and Pulmonary
Plexuses
Splanchnic
Nerves
Pre
Post
Ganglionic

27. Sympathetic Outflow Arises from spinal cord segments T1 through L2
Sympathetic neurons produce the lateral horns of the spinal cord
Postganglionic fibers innervate the numerous organs of the body

28. Sympathetic Chain
Sympathetic neurons go up and down the sympathetic chain, in order to provide reduncancy.

29. Visceral Reflexes
Some people consider the autonomic nervous system to be a purely motor system, despite the presence of the sensory neurons.
Clearly, because there are autonomic reflexes, there has to be a sensory component
Sweating

30. Visceral Reflexes

31. Referred Pain
Pain stimuli arising from the viscera are carried in sympatheric nerves.
Often visceral pain is perceived as somatic in origin

32. Referred Pain
This may be due to the fact that visceral pain afferents “piggyback” on somatic pain fibers

33. Interactions of the Autonomic Divisions
The parasympathetic and sympathetic nervous systems interact in three ways;
Antagonism
Tone
Cooperatively
You don’t want a picture 

34. Antagonism between the Autonomic Divisions
Most visceral organs are innervated by both sympathetic and parasympathetic fibers
This results in dynamic antagonisms that precisely control visceral activity

35. Antagonism between the Autonomic Divisions
Heart:
Sympathetic increases rate & force
Parasympathetic decreases rate & force
Lungs
Sympathetic dilates air passages
Parasynpathetic constricts air passages
Digestive System
Sympathetic decreases activity
Parasympathetic increases activity
Urinary System
Sympathetic inhibits urination
Parasympathetic promotes urination

36. ANS Tone Tone can be considered to be a system acting on it own.
Increased tone means increased activity
Decreased tone means decrease activity.
It’s a bit like a gas pedal, you control “activity” by how much you press.
Pedal to the metal equals a lot of sympathetic activity.
Foot off the gas means less sympathetic activity.
Both sympathetic tone and parasympathetic tone exist.

37. Sympathetic Tone
The sympathetic division controls blood pressure and keeps the blood vessels in a continual state of partial constriction
This sympathetic tone (vasomotor tone):
Constricts blood vessels and causes blood pressure to rise as needed
Prompts vessels to dilate if blood pressure is to be decreased

38. Sympathetic Tone
Increased Tone = Vasoconstriction Decreased Tone = Vasodilation
“Tone up the muscle”=
constriction

39. Parasympathetic Tone Parasympathetic tone:
Slows the heart
Dictates normal activity levels of the digestive and urinary systems
The sympathetic division can override these effects during times of stress

40. Parasympathetic Tone
Increase Tone = Decrease HR Decreased Tone = Increase HR

41. Cooperation between the Autonomic Divisions
ANS cooperation is best seen in control of the external genitalia
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

42. Neurotransmitters and Receptors
Acetylcholine (ACh) and norepinephrine (NE) are the two major neurotransmitters of the ANS
Cholinergic fibers – ACh-releasing fibers
Adrenergic fibers – NE-releasing fibers

43. Neurotransmitters and Receptors
Cholinergic fibers –
All preganglionic axons
All parasympathetic postganglionic axons
May bind to two different receptors
Nicotinic
Muscarinic
Adrenergic fibers –
Sympathetic postganglionic axons

44. Neurotransmitter Comparison of Somatic and Autonomic Systems
Cholinergic fibers
All preganglionic axons
All parasympathetic postganglionic axons
May bind to two different receptors
Nicotinic
Muscarinic
nAChR
mAChR NE
Adrenergic fibers –
Sympathetic postganglionic axons

45. Neurotransmitter Comparison of Somatic and Autonomic Systems
nAChR NE
mAChR
The cell bodies of postganglionic autonomic fibers are located in:

46. ANS Neurotransmitters
Neurotransmitter effects can have different effects on different targets.
Different effects are due to different receptors (α1, α2 ,β1, β2)
NTs can be excitatory or inhibitory depending upon the receptor type. In adrenergic receptors, α1 is stimulatory and α2 is inhibitory
Different organs carry different receptors. For example, there are α NE receptors in blood vessels and β NE receptors in cardiac muscle.
This allows pharmaceutical targeting.

47. Noradrenergic Receptors
Two main types ( and ) and subdivisions:
Allows stimulation of some things (bronchodilation) without affecting heart rate.
 and  ADRENERGIC RECEPTORS
1 – stimulation
2 – inhibition
1 – stimulation
2 – inhibition

48. NE Pharmaceuticals
1 stimulants would constrict blood vessels and dilate the eyes.
2 stimulants promote blood clotting
1 stimulants increase HR and beat strength.
2 stimulants dilate bronchials and coronary vessels. More air, more blood.
You are inhibiting sympathetic tone, thus causing dilation.

50. Cholinergic Receptors
The two types of receptors that bind ACh are nicotinic and muscarinic
These are named after drugs that bind to them and mimic ACh effects

51. Cholinergic Receptors

52. Nicotinic Receptors Nicotinic receptors are found on:
Motor end plates (somatic targets)
All ganglionic neurons of both sympathetic and parasympathetic divisions
The hormone-producing cells of the adrenal medulla
The effect of ACh binding to nicotinic receptors is always stimulatory

53. Comparison of Somatic and Autonomic Systems
nAChR
mAChR NE

54. Muscarinic Receptors
Muscarinic receptors occur on all effector cells stimulated by postganglionic cholinergic fibers
The effect of ACh binding:
Can be either inhibitory or excitatory
Depends on the receptor type of the target organ
Slows heart rate and strength of muscle contractions
Increases digestive activity
Constriction of the iris

55. Effects of Drugs Atropine – blocks parasympathetic effects
Bella donna (and antidote to nerve gas)
Neostigmine – inhibits acetylcholinesterase and is used to treat myasthenia gravis
Tricyclic antidepressants – prolong the activity of NE on postsynaptic membranes
Over-the-counter drugs for colds, allergies, and nasal congestion – stimulate -adrenergic receptors
Beta-blockers – attach mainly to 1 adrenergic receptors and reduce heart rate and prevent arrhythmias

56. Cholinergic blockers
Muscarinic blockers block parasympathetic effects on target organs.
Atropine used topically during eye exams to dilate pupils
May be used to reduce salivation and respiratory secretions.

57. Drugs that Influence the ANS

58. Drugs that Influence the ANS

59. Localized Versus Diffuse Effects
The parasympathetic division exerts short-lived, highly localized control
The sympathetic division exerts long-lasting, diffuse effects

60. Effects of Sympathetic Activation
Sympathetic activation is long-lasting because NE:
Is inactivated more slowly than ACh
Is an indirectly acting neurotransmitter, using a second-messenger system
Epinephrine is released into the blood and remains there until destroyed by the liver

61. Levels of ANS Control
The hypothalamus is the main integration center of ANS activity
Subconscious cerebral input via limbic lobe connections influences hypothalamic function
Other controls come from the cerebral cortex, the reticular formation, and the spinal cord

62. Levels of ANS Control

63. Hypothalamic Control Centers of the hypothalamus control:
Heart activity and blood pressure
Body temperature, water balance, and endocrine activity
Emotional stages (rage, pleasure) and biological drives (hunger, thirst, sex)
Reactions to fear and the “fight-or-flight” system