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PowerPoint® Lecture Slides
prepared by Leslie Hendon,
University of Alabama,
Birmingham
15
HUMAN
ANATOMY
fifth edition
MARIEB | MALLATT | WILHELM
PART 2
The
Autonomic
Nervous
System and
Visceral
Sensory
Neurons
Copyright © 2008 Pearson Education, Inc.,
publishing as Benjamin Cummings
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
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Sacral Outflow

Axons run in ventral roots to ventral rami
 Form splanchnic nerves
 Run through the inferior hypogastric plexus
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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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Sympathetic Trunk Ganglia


Located on both sides of the vertebral column
Linked by short nerves into sympathetic trunks
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Sympathetic Trunk Ganglia


Joined to ventral rami by white and gray rami
communicantes
Fusion of ganglia  fewer ganglia than spinal
nerves
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Sympathetic Trunk Ganglia
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Figure 15.8
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,
and inferior hypogastric ganglia
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Sympathetic Division of the ANS
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Figure 15.7
Sympathetic Pathways to the Body Periphery

Innervate
 Sweat glands
 Arrector pili muscles
 Peripheral blood vessels
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Sympathetic Pathways to the Body Periphery
Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings
Figure 15.9
Sympathetic Pathways to the Head


Preganglionic fibers originate in spinal cord at
T1–T4
Fibers ascend in the sympathetic trunk
 Synapse in superior cervical ganglion
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Sympathetic Pathways to the Head

Postganglionic fibers associate with large arteries
 Carried by these structures to
 Glands
 Smooth muscle
 Vessels throughout the head
Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings
Sympathetic Pathways to the Head
Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings
Figure 15.10
Sympathetic Pathways to Thoracic Organs



Preganglionic fibers originate at spinal levels T1–
T6
Some fibers synapse in nearest sympathetic trunk
ganglion
Postganglionic fibers run directly to the organ
supplied
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Sympathetic Pathways to Thoracic Organs


Sympathetic fibers to heart have a less direct
route
Functions
 Increase heart rate
 Dilate bronchioles
 Dilate blood vessels to the heart wall
 Inhibit muscles and glands in the esophagus and
digestive system
Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings
Sympathetic Pathways to Thoracic Organs
Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings
Figure 15.11
Sympathetic Pathways to Abdominal Organs


Preganglionic fibers originate in spinal cord (T5–
L2)
Pass through adjacent sympathetic trunk ganglia
 Then travel in thoracic splanchnic nerves
 Synapse in prevertebral ganglia on the abdominal
aorta
 Celiac and superior mesenteric ganglia
 Inhibit activity of muscles and glands in visceral
organs
Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings
Sympathetic Pathways to the Abdominal Organs
Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings
Figure 15.12
Sympathetic Pathways to the Pelvic Organs




Preganglionic fibers originate in spinal cord
(T10 –L2)
Some fibers synapse in sympathetic trunk
Other preganglionic fibers synapse in prevertebral
ganglia
Postganglionic fibers proceed from plexuses to
pelvic organs
Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings
Sympathetic Pathways to the Pelvic Organs
Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings
Figure 15.13
The Role of the Adrenal Medulla in the Sympathetic Division




Major organ of the sympathetic nervous system
Constitutes largest sympathetic ganglia
Secretes great quantities of norepinephrine and
adrenaline
Stimulated to secrete by preganglionic
sympathetic fibers
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The Adrenal Medulla
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Figure 15.14
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Table 15.2 (1 of 3)
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Table 15.2 (2 of 3)
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Table 15.2 (3 of 3)
Visceral Sensory Neurons

General visceral sensory neurons monitor
 Stretch, temperature, chemical changes, and
irritation


Cell bodies are located in the dorsal root ganglion
Visceral pain – perceived to be somatic in origin
 referred pain
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A Map of Referred Pain
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Figure 15.15
Visceral Reflexes

Visceral sensory and autonomic neurons
 Participate in visceral reflex arcs
 Defecation reflex
 Micturition reflex


Some are simple spinal reflexes
Others do not involve the CNS
 Strictly peripheral reflexes
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Visceral Reflex Arc
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Figure 15.16
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
Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings
Central Control of the ANS
Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings
Figure 15.17
Disorders of the Autonomic Nervous System

Raynaud’s disease – characterized by constriction
of blood vessels
 Provoked by exposure to cold or by emotional
stress

Hypertension – high blood pressure
 Can result from overactive sympathetic
vasoconstriction
Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings
Disorders of the Autonomic Nervous System

Mass reflex reaction
 Uncontrolled activation of autonomic and somatic
motor neurons
 Affects quadriplegics and paraplegics

Achalasia of the cardia
 Defect in the autonomic innervation of the
esophagus
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The ANS Throughout Life



Preganglionic neurons of the ANS develop from
the neural tube
Ganglionic neurons develop from the neural crest
Development of the sympathetic division
 Some cells migrate ventrally
 Form the sympathetic trunk ganglia
 Other cells migrate
 Form the prevertebral ganglia
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The ANS Throughout Life
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Figure 15.18
The ANS Throughout Life

Efficiency of the ANS declines with advancing
age
 Constipation due to reduced mobility of
gastrointestinal (GI) tract
 Dry eyes due to reduced tear formation
Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings