1. Copyright © 2005 Pearson Education, Inc
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2. Objectives
What is Autonomic Nervous System.
Describe Sympathetic and Parasympathetic Nervous System.
Give their Functions.

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4. The Autonomic Nervous System and Visceral Sensory Neurons
1- Innervates smooth muscle, cardiac muscle, and glands
2- Regulates visceral functions:
A) Heart rate, blood pressure, digestion, urination
B) The general visceral motor division of the PNS
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5. The Autonomic Nervous System and Visceral Sensory Neurons
Figure 15.1
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6. Comparison of Autonomic and Somatic Motor Systems
One motor neuron extends from the CNS to skeletal muscle
Axons are well myelinated, conduct impulses rapidly
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8. Comparison of Autonomic and Somatic Motor Systems
Autonomic nervous system
Chain of two motor neurons
Preganglionic neuron
Postganglionic neuron
Conduction is slower due to thinly or unmyelinated axons
Pre-ganglionic
Post-ganglionic
Ganglion
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9. Autonomic and Somatic Motor Systems
Figure 15.2
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10. Divisions of the Autonomic Nervous System
Sympathetic and parasympathetic divisions
Innervate mostly the same structures
Cause opposite effects
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11. Divisions of the Autonomic Nervous System
Sympathetic – “fight, flight, or fright”
Activated during exercise, excitement, and emergencies
Parasympathetic – “rest and digest”
Concerned with conserving energy
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12. Anatomical Differences in Sympathetic and Parasympathetic Divisions
Issue from different regions of the CNS
Sympathetic – also called the thoracolumbar division
Parasympathetic – also called the craniosacral division
Figure 15.3
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13. Anatomical Differences in Sympathetic and Parasympathetic Divisions
Length of postganglionic fibers
Sympathetic – long postganglionic fibers
Parasympathetic – short postganglionic fibers
Branching of axons
Sympathetic axons – highly branched
Influences many organs
Parasympathetic axons – few branches
Localized effect
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14. Neurotransmitters of Autonomic Nervous System
Neurotransmitter released by preganglionic axons
Acetylcholine for both branches (cholinergic)
Neurotransmitter released by postganglionic axons
Sympathetic – most release norepinephrine (adrenergic)
Parasympathetic – release acetylcholine
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15. Anatomical Differences in Sympathetic and Parasympathetic Divisions
Figure 15.4a
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16. Anatomical Differences in Sympathetic and Parasympathetic Divisions
Figure 15.4b
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17. The Parasympathetic Division
Cranial outflow
Comes from the brain
Innervates organs of the head, neck, thorax, and abdomen
Sacral outflow
Supplies remaining abdominal and pelvic organs
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18. The Parasympathetic Division
Figure 15.5
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19. Preganglionic fibers run via:
Cranial Outflow
Preganglionic fibers run via:
Oculomotor nerve (III)
Facial nerve (VII)
Glossopharyngeal nerve (IX)
Vagus nerve (X)
Cell bodies located in cranial nerve nuclei in the brain stem
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20. Sacral outflow (S2-4): form pelvic splanchnic nerves
Cranial outflow
III - pupils constrict
VII - tears, nasal mucus, saliva
IX – parotid salivary gland
X (Vagus n) – visceral organs of thorax & abdomen:
Stimulates digestive glands
Increases motility of smooth muscle of digestive tract
Decreases heart rate
Causes bronchial constriction
Sacral outflow (S2-4): form pelvic splanchnic nerves
Supply 2nd half of large intestine
Supply all the pelvic (genitourinary) organs
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21. 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
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22. Parasympathetic Nervous System: 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 splanchnic nerves
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23. Functions of Parasympathetic Nervous System
Decreased Heart Rate
Decreased Blood Pressure
Pupil Constriction
Increased Urination
Decreased Sweating
Bronchial Constriction
Increased Salivation
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24. The Sympathetic Division
Basic organization
Issues from T1-L2
Preganglionic fibers form the lateral gray horn
Supplies visceral organs and structures of superficial body regions
Contains more ganglia than the parasympathetic division
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25. Functions of Sympathetic Nervous System
Increased Heart Rate
Increased Blood Pressure
Pupil Dilation
Decreased Urination
Increased Sweating
Bronchial Dilation
Decreased Salivation
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26. Sympathetic Trunk Ganglia
Located on both sides of the vertebral column
Linked by short nerves into sympathetic trunks
Joined to ventral rami by white and gray rami communicantes
Fusion of ganglia  fewer ganglia than spinal nerves
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27. Regardless of target, all begin same
Preganglionic axons exit spinal cord through ventral root and enter spinal nerve
Exit spinal nerve via communicating ramus
Enter sympathetic trunk/chain where postganglionic neurons are
Has three options…
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28. Options of preganglionic axons in sympathetic trunk
Synapse on postganglionic neuron in chain ganglion then return to spinal nerve and follow its branch to the skin
Ascend or descend within sympathetic trunk, synapse with a posganglionic neuron within a chain ganglion, and return to spinal nerve at that level and follow branches to skin
Enter sympathetic chain, pass through without synapsing, form a splanchnic nerve that passes toward thoracic or abdominal organs
These synapse in prevertebral ganglion in front of aorta
Postganglionic axons follow arteries to organs
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30. Sympathetic Pathways to Periphery:Synapse in chain ganglia at same level or different level
Figure 15.9
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31. Pass through ganglia and synapse in prevertebral ganglion
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32. Sympathetic Trunk Ganglia
Figure 15.8
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35. Unpaired, not segmentally arranged Occur only in abdomen and pelvis
Prevertebral Ganglia
Unpaired, not segmentally arranged
Occur only in abdomen and pelvis
Lie anterior to the vertebral column
Main ganglia
Celiac, superior mesenteric, inferior mesenteric, inferior hypogastric ganglia
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36. Sympathetic Division of the ANS
Figure 15.7
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37. Sympathetic Pathways to the Head
Figure 15.10
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38. Sympathetic Pathways to Thoracic Organs
Figure 15.11
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39. Sympathetic Pathways to the Abdominal Organs
Figure 15.12
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40. Sympathetic Pathways to the Pelvic Organs
Figure 15.13
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41. The Role of the Adrenal Medulla in the Sympathetic Division
Major organ of the sympathetic nervous system
Secretes great quantities epinephrine (a little norepinephrine)
Stimulated to secrete by preganglionic sympathetic fibers
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42. The Adrenal Medulla Figure 15.14
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43. Visceral Sensory Neurons
General visceral sensory neurons monitor:
Stretch, temperature, chemical changes, and irritation
Cell bodies are located in the dorsal root ganglia
Visceral pain – perceived to be somatic in origin
Referred pain
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44. A Map of Referred Pain Figure 15.15
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45. Visceral sensory and autonomic neurons
Visceral Reflexes
Visceral sensory and autonomic neurons
Participate in visceral reflex arcs
Defecation reflex
Micturition reflex
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46. Visceral Reflex Arc Figure 15.16
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47. Central Control of the ANS
Control by the brain stem and spinal cord
Reticular formation exerts most direct influence
Medulla oblongata
Periaqueductal gray matter
Control by the hypothalamus and amygdala
Hypothalamus – the main integration center of the ANS
Amygdala – main limbic region for emotions
Control by the cerebral cortex
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48. Disorders of the Autonomic Nervous System: Raynaud’s Disease
Raynaud’s disease – characterized by constriction of blood vessels
Provoked by exposure to cold or by emotional stress
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49. Disorders of the Autonomic Nervous System: Hypertension
Hypertension – high blood pressure
Can result from overactive sympathetic vasoconstriction
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50. Disorders of the Autonomic Nervous System: Mass Reflex Reaction
Uncontrolled activation of autonomic and somatic motor neurons
Affects quadriplegics and paraplegics
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51. Disorders of the Autonomic Nervous System: Achalasia of the Cardia
Defect in the autonomic innervation of the esophagus
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