1. Chapter 14 The Autonomic Nervous System Autonomic system
System of nerves mediating involuntary actions
Regulates body organ activity
Maintains normal internal functions
Divided into sympathetic and parasympathetic divisions
Allows for varied nervous system responses in times of stress and rest

2. A schematic of the somatic nervous system
(SNS), which provides conscious and sub-
Conscious control over skeletal muscles
Upper motor
neurons in
primary motor
cortex
BRAIN
Somatic motor
nuclei of brain
stem
Skeletal
muscle
Lower
motor
neurons
Spinal cord
Figure 14 Section 1 The Functional Anatomy and Organization of the Autonomic Nervous System (ANS)
Somatic
motor
nuclei of
spinal cord
Skeletal
muscle
Figure 14 Section 2

3. Comparison of the Somatic and Autonomic Nervous Systems: Functional Organization
Somatic nervous system (SNS)
Includes processes perceived or controlled consciously
Somatic sensory portion
detects stimuli from special senses, skin, and proprioceptors
sends information to CNS
Somatic motor portion
transmits nerve signals from CNS to control skeletal muscles

4. Comparison of the Somatic and Autonomic Nervous Systems: Functional Organization
Autonomic nervous system (ANS)
Includes processes regulated below conscious level
Visceral sensory portion
detects stimuli from blood vessels and internal organs
Autonomic motor portion (visceral motor)
transmits nerve signals to cardiac muscle, smooth muscle, and glands
Functions to maintain homeostasis
constant internal environment
Regulates:
heart rate and blood pressure
respiratory rate, sweating, and digestion
Keeps these variables within optimal ranges

5. Figure 15.1a Somatic Nervous System Posterior root ganglion
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Somatic Nervous System
Figure 15.1a
Posterior root ganglion
Anterior root
Somatic sensory
neuron detects stimuli
and transmits nerve
signals from skin,
skeletal muscle, joints,
and special senses
(vision, hearing, etc.).
Somatic motor neuron
sends nerve signals to
skeletal muscle.
Skeletal muscle
Sensory receptor
in skin
(a)

6. Figure 15.1b Autonomic Nervous System Autonomic ganglion
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Autonomic Nervous System
Figure 15.1b
Autonomic
ganglion
Preganglionic autonomic motor neuron
transmits nerve signals to a ganglionic
motor neuron.
Ganglionic autonomic
motor neuron transmits
nerve signals to smooth
muscle, cardiac muscle,
and glands.
Visceral sensory
neuron detects
stimuli within blood
vessels and smooth
muscle in the
viscera.
Smooth muscle
in trachea
Sensory receptor
in viscera
(b)

7. Divisions of the Autonomic Nervous Systems: Functional Differences
Motor component of ANS
Subdivided into parasympathetic and sympathetic divisions
Parasympathetic division
functions to maintain homeostasis at rest
energy conservation and replenishing stage
“rest-and-digest” division
Sympathetic division
prepares the body for emergencies
“fight-or-flight” division
increased alertness and metabolic activity
“three E’s”: emergency, exercise, or excitement

8. Autonomic Nervous System
Sympathetic Division
Parasympathetic Division
In the sympathetic division, or thoracolumbar
(thor-a-kō-LUM-bar) division, axons emerge from
the thoracic and superior lumbar segments of the
spinal cord and innervate ganglia relatively close
to the spinal cord.
In the parasympathetic division, or cranio-
sacral (krā-nē-ō-SĀ-krul) divions, axons
emerge from the brain stem and the sacral
segments of the spinal cord, and they innervate
ganglia very close to (or within) target organs.
Cranial nerves
(III, VII, IX, and X) T1 T2 T3 T4
The two main divisions
of the ANS: the sympathetic
and parasympathetic
divisions T5 T6
Thoracic
nerves T7 T8 T9
T10
Figure The ANS consists of sympathetic, parasympathetic, and enteric divisions
T11
T12 L1
Lumbar nerves
(L1, L2 only) L2 S2 S3
Sacral nerves
(S2, S3, S4 only) S4
Figure 8

9. Divisions of the Autonomic Nervous Systems: Anatomic Differences
Parasympathetic
Preganglionic neuron in brainstem or S2-S4 spinal cord
Termed craniosacral division
Ganglionic neuron innervating muscles or glands
Preganglionic axons longer
Postganglionic axons shorter
Few preganglionic axons
Ganglia close to or within effector
Sympathetic
Preganglionic neuron in lateral horns of T1-L2
Termed thoracolumbar division
Ganglionic neuron innervating muscles or glands
Preganglionic axons shorter
Postganglionic axons longer
Many preganglionic axons
Ganglia relatively close to spinal cord (in sympathetic trunk ganglia or prevertebral ganglia)

10. Figure 15.3 Autonomic Motor Nervous System Parasympathetic Division
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Autonomic Motor Nervous System
Parasympathetic Division
Sympathetic Division
Origin:
Preganglionic neurons located
in brainstem nuclei and S2–S4
segments of spinal cord
(craniosacral)
Origin:
Preganglionic neurons
located in lateral horns of
T1– L2 segments of spinal
cord (thoracolumbar)
CN III (oculomotor)
CN VII (facial)
Functions:
• “Rest-and-digest” response
• Brings body to homeostasis
CN IX (glossopharyngeal)
Functions:
• Activated in emergency
situations
• “Fight-or-flight” response
• Also involved with
homeostasis
Sympathetic trunk
CN X (vagus)
T1–L2 segments
of spinal cord
S2–S4 segments
of spinal cord
Pelvic splanchnic
nerves

11. (close to or within effector organ wall)
Figure 15.4
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Parasympathetic Division
Sympathetic Division
Short, branching
preganglionic axon
Ganglionic
neuron
Short
postganglionic
axon
Preganglionic
neuron
Long postganglionic axon
Long preganglionic axon
Preganglionic
neuron
Ganglionic neuron
Autonomic ganglion
(close to or within effector organ wall)
Autonomic ganglion
(close to the vertebral column)
(a)
(b)
The parasympathetic division has short axons with relatively few branches and ganglia located close to or within the wall of the organ.
The sympathetic division has long axons with many branches and ganglia located in the sympathetic trunk or prevertebral ganglia

12. Parasympathetic Division: Cranial Components
Oculomotor(lens & iris), facial(lacrimal glands), and glossopharyngeal nerves(parotid)
convey parasympathetic information to the head
Vagus nerve
parasympathetic information for thoracic and most abdominal organs
increased mucus production and decreased airway diameter
decrease in heart rate and force
causes increased smooth muscle motility and secretory activity

13. Parasympathetic Division: Cranial Components
Which four cranial nerves have a parasympathetic component? What organs are innervated by each?
The oculomotor nerve innervates the ciliary and constrictor muscles of the eye.
The facial nerve innervates the lacrimal, submandibular, and sublingual glands.
The glossopharnygeal nerve innervates the parotid salivary gland.
The vagus nerve innervates the thoracic organs, most of the abdominal organs, and the gonads.

14. Parasympathetic Division: Pelvic Splanchnic Nerves
Target organs
Distal portion of large intestine, rectum
Bladder, distal ureter
Most reproductive organs, and others
Causes:
smooth muscle motility
secretory activity in digestive tract
contraction in bladder wall
erection of clitoris and penis
See Table 15.3: Parasympathetic Division Outflow

15. Copyright © The McGraw-Hill Companies, Inc
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Preganglionic
Ciliary ganglion
Postganglionic
Figure 15.5
Lacrimal gland
CN III
Pterygopalatine
ganglion
Parotid salivary gland
Submandibular salivary gland
Sublingual salivary gland
CN VII
Submandibular ganglion
CN IX
Otic ganglion
Pons
Heart
CN X
Cardiac plexus
Trachea
Pulmonary plexus
Esophageal plexus
Lung
Esophagus
Abdominal aortic
plexus
Liver
Gallbladder
Stomach
Spleen
Spinal cord
Kidney
Ureter
Pancreas
Small intestine
Hypogastric plexus
Testis
Ovary
Descending colon
Rectum S2 S3 S4
Pelvic splanchnic nerves
Bladder
Penis
Uterus
Vagina

16. Figure 15.7 Superior vena cava Intercostal nerve Sympathetic trunk
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Figure 15.7
Superior vena
cava
Intercostal nerve
Sympathetic trunk
Gray ramus
White ramus
Descending
thoracic aorta
Sympathetic trunk
ganglia
Azygos vein
Greater thoracic
splanchnic nerve
Diaphragm
© The McGraw-Hill Companies, Inc./Photo and Dissection by Christine Eckel

17. Sympathetic Division:
Clinical View: Horner Syndrome
Injury of cervical sympathetic trunk or T1 trunk ganglion
Symptoms on same side of head
Impairment of sympathetic signaling
Ptosis
drooping of superior eyelid
due to paralysis of superior tarsal muscle
Miosis
constricted pupil
due to paralysis of pupil dilator muscle
Anhydrosis
lack of sweating
sweat glands not receiving sympathetic innervation
Facial flushing
due to vasodilation due to lack of sympathetic innervation

18. Sympathetic Division: Sympathetic Pathways
adrenal medulla pathway
internal region of adrenal gland, adrenal medulla
directly innervated by preganglionic sympathetic axons
preganglionic neuron
extends through sympathetic trunk and prevertebral ganglia
upon stimulation, epinephrine and norepinephrine produced in medulla
circulate within blood
help prolong fight-or-flight response
prolong effects of sympathetic stimulation

19. Figure 15.8d White ramus Gray ramus Splanchnic nerve Adrenal medulla
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Figure 15.8d
White ramus
Gray ramus
Splanchnic nerve
Adrenal
medulla
Prevertebral ganglion
(no synapse occurs)
(d) Adrenal medulla pathway

20. Overview of ANS Neurotransmitters
Acetylcholine (ACh) and norepinephrine (NE)
Bind to specific receptors on postsynaptic cell
Cause stimulation or inhibition, depending on receptor
Acetylcholine
Synthesized and released by cholinergic neurons
all sympathetic and parasympathetic preganglionic neurons
all parasympathetic ganglionic neurons
neurons innervating sweat glands and blood vessels of skeletal muscle
Norepinephrine
Synthesized and released by adrenergic neurons
most other sympathetic ganglionic neurons
form network of swellings at target organ
termed varicosities
contain stored NE
NE released along length of axon

21. Figure 15.10 Preganglionic axon Autonomic ganglion
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Figure 15.10
Preganglionic axon
Autonomic ganglion
Ganglionic neuron cell body
Postganglionic axon
Varicosities
Smooth muscle cells
Mitochondrion
Synaptic vesicle
containing NE
Varicosity

22. Cholinergic Receptors
Nicotinic receptors cholinergic receptor
Sensitive to the drug nicotine
Found on all ganglionic neurons and adrenal medulla
When bound: always produces a stimulatory response
open ion channels greater movement of Na+ into cell than K+ out of cell
Muscarinic receptors cholinergic receptor
Responsive to muscarine, a mushroom toxin
Found in: all target membranes in parasympathetic division selected sympathetic cells
e.g., sweat glands in skin, blood vessels in skeletal muscle
decreases heartbeat rate
Biogenic amines (monoamines)
Bind adrenergic receptors
Catecholamines, subcategory
have catechol ring structure in molecule
include dopamine, norepinephrine, and epinephrine

23. Figure 15.9 Parasympathetic Pathway Sympathetic Pathways
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Parasympathetic Pathway
Sympathetic Pathways
Figure 15.9
Preganglionic axon
releases ACh.
ACh
ACh
ACh
Ganglionic neuron
cell body and
dendrites always
contain receptors
for ACh.
Nicotinic
receptors
Nicotinic
receptors
Nicotinic
receptors
Postganglionic axon
releases ACh or NE.
ACh
ACh NE
Muscarinic
receptors
Muscarinic
receptors
Adrenergic
receptors
Target cells contain
either ACh receptors
(bind ACh) or NE
receptors (bind NE).
Target cell
Target cell
(e.g., sweat glands
and blood vessels
in skeletal muscle)
Target cell
(e.g., most other
body structures)

24. Interactions Between the Parasympathetic and Sympathetic Divisions: Dual Innervation
Antagonistic Effects
Parasympathetic and sympathetic effects usually antagonistic
E.g., control of heart rate
parasympathetic stimulation slowing heart rate
sympathetic stimulation increasing heart rate
E.g., control of muscular activity in GI tract
parasympathetic stimulation accelerating rate of contraction and motility
sympathetic stimulation decreasing motility
E.g., control of pupil diameter in the eye
parasympathetic stimulation of circular muscle layer of iris
causes pupil constriction
sympathetic stimulation of radial muscle layer of iris
causes pupil dilation

25. Interactions Between the Parasympathetic and Sympathetic Divisions: Dual Innervation
Cooperative Effects
When both parasympathetic and sympathetic produce single result
E.g., male sexual function
penis erect due to parasympathetic innervation
ejaculation due to sympathetic innervation

26. Parasympathetic and Sympathetic Interactions: Systems Controlled Only by Sympathetic Division
Opposing effects without dual innervation
E.g., blood vessels innervated by sympathetic axons only
cause increased smooth muscle contraction and blood pressure
vasodilation achieved by decreasing stimulation below autonomic tone
E.g., sweat glands in the trunk and arrector pili muscles in the skin
cause sweating and “goosebumps”
E.g., neurosecretory cells of adrenal medulla
release epinephrine and norepinephrine, prolonging fight-or-flight effects

27. Figure 14.6.1 The ANS provides precise control over visceral functions27

28. Parasympathetic and Sympathetic Interactions: Systems Controlled Only by Sympathetic Division
Clinical View: Raynaud Syndrome
Sudden constriction of small arteries of digits
Results in loss of normal hue of distal skin
Accompanied by pain
Triggered by cold or emotional stress
Due to exaggerated local sympathetic response
More common in women

29. Control and Integration of Autonomic System Function: Autonomic Reflexes
Clinical View: Autonomic Dysreflexia
Causes blood pressure to rise profoundly
Stimulates a sympathetic reflex
causes systemic vasoconstriction
marked increase in blood pressure
Caused by hyperactivity of ANS after a spinal cord injury
Initial response to injury is spinal shock, with loss of autonomic reflexes
Abnormal response to lack of innervation, denervation hypersensitivity
e.g., involuntary relaxation of internal urethral sphincter
due to spinal cord reflex

30. Involvement of CNS ANS is a regulated nervous system, not independent
Influenced by four CNS regions:
cerebrum, hypothalamus, brainstem, and spinal cord
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Cerebrum
Conscious activities in the
cerebrum affect hypothalamus
control of the ANS
Hypothalamus
Integration and command center
for autonomic functions; involved in emotions
Brainstem
Contains major ANS reflex
centers
Spinal cord
Contains ANS reflex centers for
defecation and urination

31. Figure 14.6.1 The ANS provides precise control over visceral functions31

32. Figure 14.6.1 The ANS provides precise control over visceral functions32

33. Sympathetic Adapts body for physical activity Fight or flight
Subtle effects

34. Parasympathetic Calming effect on functions
Reduced energy expenditure and normal bodily maintenance