1. The Autonomic Nervous System
Objectives
Introduction
1. Define autonomic nervous system and explain its relationship to the peripheral nervous system.
2. Compare the somatic and autonomic nervous systems relative to effectors, efferent pathways, and
neurotransmitters released.
3. Compare and contrast the roles of the parasympathetic and sympathetic divisions.
ANS Anatomy
4. Describe the site of CNS origin, location of ganglia, and general fiber pathways for the
parasympathetic and sympathetic divisions.
ANS Physiology
5. Define cholinergic and adrenergic fibers, and list the different types of their receptors.
6. Explain the clinical importance of drugs that mimic or inhibit adrenergic or cholinergic effects.
7. Underscore the effects of the parasympathetic and sympathetic divisions on the following organs:
heart, blood vessels, gastrointestinal tract, lungs, adrenal medulla, and external genitalia.
8. Identify the autonomic nervous system controls of the spinal cord, brain stem, hypothalamus, and
cerebral cortex.
Homeostatic Imbalances of the ANS
9. Correlate the relationship of some types of hypertension, Raynaud’s disease, and the mass reflex
reaction to disorders of autonomic functioning.
Developmental Aspects of the ANS
10. Describe some effects of aging on the autonomic nervous system.
Suggested Lecture Outline
I. Introduction (pp. 533–535, Figs. 14.1–14.2)
A. Comparison of the Somatic and Autonomic Nervous System (pp. 533–535)
1. The somatic nervous system stimulates skeletal muscles, while the ANS innervates cardiac
and smooth muscle and glands.
2. In the somatic nervous system, the cell bodies of the neurons are in the spinal cord and their
axons extend to the skeletal muscles they innervate. The ANS consists of a two-neuron chain.
3. The neurotransmitter released by the somatic motor neurons is acetylcholine, which always
has an excitatory effect; the neurotransmitters released by the ANS are epinephrine and
acetylcholine, and both may have either an excitatory or an inhibitory effect.
4. There is overlap between the somatic and autonomic nervous systems, and most body
responses to changing internal and external stimuli involve both skeletal muscle activity and
visceral organ responses.
B. Divisions of the Autonomic Nervous System (p. 535)
1. The parasympathetic division keeps body energy use as low as possible while directing

2. digestion and elimination activities.
2. The sympathetic division prepares the body to respond to an emergency or threatening
situation (or vigorous exercise).
II. ANS Anatomy (pp. 535–542; Figs. 14.3–14.7; Tables 14.1–14.2)
A. Parasympathetic (Craniosacral) Division (pp. 536–538; Fig. 14.4)
1. The preganglionic axons extend from the CNS nearly all the way to the structures to be
innervated where they synapse with ganglionic neurons in the terminal ganglia.
2. The cranial outflow consists of preganglionic fibers that run in the oculomotor, facial,
glossopharyngeal, and vagus cranial nerves.
3. The rest of the large intestine and the pelvic organs are served by the sacral outflow, which
arises from neurons located in the lateral gray matter of spinal cord segments S2–S4.
B. Sympathetic (Thoracolumbar) Division (pp. 538–542; Figs. 14.5–14.6; Table 14.2)
1. The sympathetic division supplies the visceral organs in the internal body cavities but also all
visceral structures in the somatic part of the body.
2. When synapses are made in chain ganglia, the postganglionic axons enter the ventral (or
dorsal) ramus of the adjoining spinal nerves by way of communicating branches called gray
rami communicantes.
3. The preganglionic fibers from T5 down synapse in collateral ganglia; thus these fibers enter
and leave the sympathetic chains without synapsing.
4. Some fibers of the thoracic splanchnic nerves terminate by synapsing with the hormone
producing medullary cells of the adrenal cortex.
C. The visceral sensory neurons are the first link in autonomic reflexes by sending information
concerning chemical changes, stretch, and irritation of the viscera. (p. 542; Fig. 14.7)
III. ANS Physiology (pp. 543–550, Tables 14.3–14.5)
A. Neurotransmitters and Receptors (pp. 543–544; Fig. 14.8; Table 14.3)
1. Cholinergic receptors, such as nicotinic and muscarinic receptors, bind acetylcholine.
2. Adrenergic receptors alpha and beta bind to epinephrine.
B. Knowing the locations of the cholinergic and adrenergic receptor subtypes allows specific drugs
to be prescribed to obtain desired inhibitory or stimulatory effects on target organs (pp. 543–544;
Table 14.4).
C. Interactions of the Autonomic Divisions (pp. 544–547; Table 14.5)
1. Most visceral organs receive dual innervation by both ANS divisions, allowing for a dynamic
antagonism to exist between the divisions and precise control of visceral activity.
2. The sympathetic division will increase heart and respiratory rates during a fight-or-flight
situation and decrease activity of digestive and elimination organs.
3. Sympathetic tone occurs in the vascular system, and parasympathetic tone occurs in the
digestive and urinary tracts.
4. The parasympathetic and sympathetic divisions may work together to achieve a common
purpose. For example, the parasympathetic division controls erection while the sympathetic
division controls ejaculation.
5. The sympathetic division mediates reflexes that regulate body temperature, release renin
from the kidneys, and promote metabolic effects.
6. The parasympathetic division exerts short-lived, localized control over its effectors, while the
sympathetic division responds in a diffuse and interconnected way to cause a body-wide

3. mobilization.
D. Control of Autonomic Functioning (pp. 547–550, Fig. 14.9)
1. The brain stem appears to exert the most direct influence over autonomic functions.
2. The hypothalamus is the main integration center for the autonomic nervous system.
3. Cortical or voluntary control of the autonomic nervous system does appear to be possible.
IV. Homeostatic Imbalances of the ANS (pp. 550–551)
A. Hypertension, or high blood pressure, may result from an overactive sympathetic vasoconstrictor
response due to continuous high levels of stress.
B. Raynaud’s disease is characterized by intermittent attacks causing the skin of the fingers and the
toes to become pale, then cyanotic and painful.
C. Mass reflex reaction is a life-threatening condition involving uncontrolled activation of both
somatic and autonomic motor neurons.
V. Developmental Aspects of the ANS (p. 551)
A. Embryonic and fetal development of the autonomic nervous system
1. ANS preganglionic neurons and somatic motor neurons derive from the embryonic neural
tube.
2. ANS structures found in the PNS (ganglionic neurons, adrenal medulla, and all autonomic
ganglia) derive from the neural crest.
3. Nerve growth factor is a protein secreted by target cells of the postganglionic axons.
B. In old age the efficiency of the ANS begins to decline, partly due to structural changes of some
preganglionic axonal terminals.
Cross References
Additional information on topics covered in Chapter 14 can be found in the chapters listed below.
1. Chapter 3: Membrane functions; membrane receptors
2. Chapter 4: Nervous tissue
3. Chapter 11: Membrane potentials; neuronal integration; serial and parallel processing; synapses;
neurotransmitters
4. Chapter 12: Ascending and descending tracts of the spinal cord; spinal roots; gray and white matter of
the spinal cord
5. Chapter 18: The role of the sympathetic and parasympathetic pathways (as well as epinephrine and
norepinephrine) in medullary control of cardiac rate
6. Chapter 19: Sympathetic control of blood vessel diameter
7. Chapter 23: Sympathetic and parasympathetic control of digestive processes
8. Chapter 25: Sympathetic control of blood vessels to the kidney; parasympathetic pelvic splanchnic
nerves and the urinary system
9. Chapter 27: Sympathetic and parasympathetic effects in human sexual response
Laboratory Correlations
1. Marieb, E. N. Human Anatomy & Physiology Laboratory Manual: Cat and Fetal Pig Versions. Eighth
Edition Updates. Benjamin Cummings, 2006.

4. Exercise 21: Spinal Cord, Spinal Nerves, and Autonomic Nervous System
2. Marieb, E. N. Human Anatomy & Physiology Laboratory Manual: Main Version. Seventh Edition
Update. Benjamin Cummings, 2006.
Exercise 21: Spinal Cord, Spinal Nerves, and Autonomic Nervous System
Histology Slides for the Life Sciences
Available through Benjamin Cummings, an imprint of Pearson Education, Inc. To order, contact your
local Benjamin Cummings sales representative.
Slide 73 Myelinated Nerve Cross Section—Myelin Sheaths.
Slide 74 Myelinated Nerve Longitudinal Section—Nodes of Ranvier.
Slide 75 Efferent (Motor) Neuron.
Slide 76 Spinal Cord Bottom, Stained for Axons.
Lecture Hints
1. Since the autonomic nervous system is more complex than the somatic nervous system, it is
worthwhile to spend some time comparing and contrasting the anatomy of each.
2. Figure 14.4 is a good 3-D representation of parasympathetic pathways; however, as an initial intro-duction
during lecture, it might be useful to use the enlarged transparency Figure 14.3, or to draw a 2-
D schematic diagram of sympathetic and parasympathetic pathways, so that the class can follow the
construction of the circuit logically and understand how it is “wired.” Then refer students to the
overall construction presented in Figure 14.4, p. 536.
3. Emphasize that somatic efferent pathways consist of a motor neuron cell body in the CNS whose axon
extends out through the PNS to directly innervate the skeletal muscle effector. In contrast, autonomic
efferent pathways follow the same general plan, but consist of two motor neurons in series.
4. Point out that in many cases sympathetic and parasympathetic synapses use different neuro-transmitters,
an essential characteristic in the dual nature of autonomic function. This will be
illustrated when discussing fight/flight and rest/digest responses.
5. Many students have difficulty with the idea of neurotransmitter/receptor function. Point out that many
substances similar in chemical construction to the actual neurotransmitter are capable of generating
the same response. Emphasize that it is the binding of a substance to a receptor that generates the
cellular response.
6. To illustrate sympathetic tone, use the example of vasomotor control. Point out that dilation (to
decrease blood pressure) is not a muscle contraction response, but that relaxation of the smooth
muscle in the wall of the blood vessel is the actual cause. To vasoconstrict, increase sympathetic
stimulation. Therefore, in order for dilation to be possible, there must be a certain amount of constant
sympathetic stimulation (tone) even during a relaxed state.
7. Emphasize that there is a constant level of parasympathetic stimulation (tone) to many visceral organs
and that there is just enough sympathetic stimulation to keep systems in homeostasis. To probe the
students ask, “What would happen to resting heart rate if parasympathetic stimulation were cut?”
Activities/Demonstrations
1. Audio-visual materials listed under Multimedia in the Classroom and Lab.
2. Set up a live, exposed frog or turtle heart demonstration to illustrate the effects of acetylcholine and
epinephrine.

5. 3. Without announcing what you will be doing, walk quietly into the lecture room, set your notes down,
and yell very loudly (to startle the students). Then, have each student prepare a list of all those organs
that were affected and what the effects were.
4. Obtain a preserved cat and dissect it to illustrate the sympathetic nerve trunk, celiac ganglia,
splanchnic nerves, and other portions of the ANS.
5. Obtain a 3-D model of a spinal cord cross section and longitudinal section that illustrate the parts of
the ANS and especially the sympathetic, gray, and white rami.
Critical Thinking/Discussion Topics
1. Describe the role of beta blockers in treating certain types of visceral disorders.
2. At certain times when people are very excited or are shocked suddenly, their bowels and/or urinary
sphincters lose control. In terms of the role of the ANS, why does this happen?
3. Some individuals, following a very stressful event such as final exams, frequently come down with
colds. Is there any relationship between the ANS, stress, and the onset of an illness? Discuss.
4. Most people feel very tired after they eat a big meal. Why?
5. How can biofeedback be used to reduce effects of constant pain and stress?
6. Why is sympathetic action diffuse and long-lasting while parasympathetic is local and short-lived?
What would happen to body systems during a stressful situation if these characteristics were reversed?
How would anatomy have to be changed?
Library Research Topics
1. Do all animals have an autonomic nervous system? If so, is it more or less advanced than ours?
2. The ANS regulates peristaltic waves of the GI tract. If the ganglia and/or fibers controlling this
activity were damaged, what would happen? What bacterial agents or type of trauma could cause this?
3. Ulcers seem to occur in hypertensive individuals. What are the causes of this problem and what
treatment is available?
4. Nicotine and muscarine are substances that bind at specific receptors. What exactly do these receptors
look like? Draw a cell membrane and illustrate how the receptors might look.
Multimedia in the Classroom and Lab
Online Resources for Students
www.anatomyandphysiology.com www.myaandp.com
The following shows the organization of the Chapter Guide page in both the Anatomy &
Physiology Place and MyA&P™. The Chapter Guide organizes all the chapter-specific
online media resources for Chapter 14 in one convenient location, with e-book links to
each section of the textbook. Please note that both sites also give you access to other
®
general A&P resources, like InterActive Physiology
, PhysioEx 6.0™, Anatomy 360°,
Flashcards, a Glossary, a Histology Tutorial, and much more.
Objectives
Section 14.1 Introduction (pp. 533–535)
Section 14.2 ANS Anatomy (pp. 535–543)

6. Memory: Autonomic Pathways
Memory: The Major Ganglia of the Autonomic Nervous System
Section 14.3 ANS Physiology (pp. 543–547, 550)
Section 14.4 Homeostatic Imbalances of the ANS (pp. 550–551)
Case Study: Nervous Tissues
Case Study: Cardiac Arrhythmia
Section 14.5 Developmental Aspects of the ANS (p. 551)
Chapter Summary
Self-Study Quizzes
Art Labeling Quiz
Matching Quiz
Multiple-Choice Quiz (Level I)
Multiple-Choice Quiz (Level II)
True-False Quiz
Crossword Puzzles
Crossword Puzzle 14.1
Crossword Puzzle 14.2
Media
See Guide to Audio-Visual Resources in Appendix A for key to AV distributors.
Video
1. Biologix: The Neuroendocrine System (IM, UL; 29 min., 1997). This video compares the nervous and
endocrine system by describing how each responds to situations of physical activity, changes in body
temperature, eating, and stress.
2. Brain and Nervous System: Your Information Superhighway (FHS; 25 min., 2000). This program
explores the brain and nervous system using the analogy of computers and the Internet.
3. Managing Stress (FHS; 19 min.). Demonstrates the difference between positive stress, which
strengthens the immune system, and negative stress, which can increase the likelihood of illness.
Excellent aid to encourage class understanding of complicated concepts.
4. Nerve Impulse Conduction (IM; 29 min., 1997). This video explores the electrochemical nature of
nerve impulse conduction and transmission. It uses simulations to analyze the different stages of
membrane potential and presents research on how chemicals affect membrane potential.
5. The Nervous System: The Ultimate Control Center (KV; 20 min., 2001). This video explores
voluntary and autonomic functions, the central nervous system, and the network of nerves and other
structures that make up the peripheral nervous system.
6. Stress and Immune Function (FHS; 26 min., 1986). Presents an in-depth examination of the
relationship between stress and illness. Encourages class discussion.
Software
1. A.D.A.M.® InterActive Anatomy® 4.0 (see p. 9 of this guide for full listing).
2. A.D.A.M.® MediaPro (see p. 9 of this guide for full listing).
3. A.D.A.M.® Anatomy Practice (see p. 86 of this guide for full listing).
4. Bodyworks (see p. 9 of this guide for full listing).
5. InterActive Physiology 9-System Suite CD-ROM: Nervous System I and II (see p. 148 for full listing).
6. The Ultimate Human Body (see p. 9 of this guide for full listing).

7. Lecture Enhancement Material
To view thumbnails of all of the illustrations for Chapter 14, see Appendix B.
Transparencies Index/Media Manager
Figure 14.1 Place of the ANS in the structural organization of the nervous system.
Figure 14.2 Comparison of somatic and autonomic nervous systems.
Figure 14.3 Overview of the subdivisions of the ANS.
Figure 14.4 Parasympathetic (craniosacral) division of the ANS.
Figure 14.5 Sympathetic (thoracolumbar) division of the ANS.
Figure 14.6 Sympathetic trunks and pathways.
Figure 14.7 Visceral reflexes.
Figure 14.8 Referred pain.
Figure 14.9 Levels of ANS control.
Table 14.1 Anatomical and Physiological Differences Between the Parasympathetic and Sympathetic
Divisions
Table 14.2 Segmental Sympathetic Supplies
Table 14.3 Cholinergic and Adrenergic Receptors
Table 14.4 Selected Drug Classes That Influence the Activity of the Autonomic Nervous System
Table 14.5 Effects of the Parasympathetic and Sympathetic Divisions on Various Organs
Answers to End-of-Chapter Questions
Multiple Choice and Matching Question answers appear in Appendix G of the main text.
Short Answer Essay Questions
6. Involuntary nervous system is used to reflect its subconscious control; emotional-visceral system
reflects the fact that the hypothalamus is the major regulatory center for both the emotional (limbic)
response and visceral controls. The term visceral also indicates the location of most of its effectors. (p.
533)
7. White rami contain myelinated preganglionic fibers that leave the spinal nerve to enter the
paravertebral ganglion; gray rami represent axons of postganglionic neurons, are unmyelinated, and
enter the spinal nerve to travel to their ultimate destination. (p. 541)
8. Sweat glands—increase the production of sweat; eye pupils—enlarge (dilate); adrenal medulla—
releases norepinephrine and epinephrine; heart—increase in rate and force of contraction; lungs—
bronchodilation; liver—glycogenolysis and the release of glucose to the blood; blood vessels to the
skeletal muscles—dilation; blood vessels to digestive viscera—constriction; salivary glands—
constriction of blood vessels supplying the gland, causing a decrease in saliva production. (p. 546)
9. All except the effects on the adrenal medulla, liver, and blood vessels. (p. 546)
10. All preganglionic fibers and postganglionic fibers of the parasympathetic division secrete
acetylcholine. Some postganglionic sympathetic fibers secrete acetylcholine. Only postganglionic
fibers of sympathetic division release norepinephrine. (p. 543)
11. Sympathetic tone means that the vascular system is under a partial state of contraction.
Parasympathetic tone maintains the tone of the digestive organs and keeps heart rate at the lowest
level that maintains homeostasis. (p. 545)
12. Acetylcholine—nicotinic and muscarinic; norepinephrine—alpha 1, alpha 2, ß1, ß2. See Table 14.3

8. for major locations. (p. 544)
13. The reticular formation nuclei in the brain stem, particularly those in the medulla. (p. 550)
14. The hypothalamus is the main integration center that coordinates heart rate, blood pressure, and body
temperature. (p. 550)
15. The premise of biofeedback training is that we do not routinely exert voluntary controls over our
visceral activities because we have little conscious awareness of our internal environment. The
training allows subjects to become aware of the body’s signals and subsequently make subtle internal
changes to help them control such things as migraine headaches and stress. (p. 550)
16. Elderly people often complain of constipation and dry eyes, and faintness when they change position,
e.g., stand up abruptly after sitting. (p. 551)
17. The cell body of the preganglionic neuron resides in the CNS, whereas the ganglionic neuron’s cell
body lies in the autonomic ganglion, not distal (“post”) to the ganglion. However, its axon does lie
distal to the ganglion, therefore, the term postganglionic axon is correct. (p. 538)
Critical Thinking and Clinical Application Questions
1. Parasympathetic stimulation of the bladder via the release of acetylcholine increases bladder tone and
releases the urinary sphincters, a result which will be reproduced by bethanechol. He will probably
experience dizziness due to low blood pressure (decreased heart rate), deficient tear formation,
wheezing, diarrhea, cramping, and undesirable erection of the penis—all parasympathetic effects. (p.
545)
2. Referred pain is the sensation of pain that appears to originate from a site other than that of the painful
stimulus. Damage to the heart gives rise to pain impulses that enter the spinal cord in the thoracic
region, and also receives impulses from the left chest and arm. (p. 543)
3. Raynaud’s disease. Smoking causes vasoconstriction, i.e., the nicotine mimics the affects of
acetylcholine on sympathetic nicotinic receptors of the skin blood vessels. (p. 551)
4. Tiffany may temporarily experience light-headedness, blurred vision, dry mouth, constipation, and
difficulty urinating or incontinence.
5. The smell stimulates the olfactory nerves and carries the information to the CNS. The response is
parasympathetic activation, which stimulates increased salivary gland secretion (mouth watering) and
increased secretory activity and motility of the stomach (stomach rumbling). (pp. 545–546)
6. Raynaud’s disease. The fingertips turn cyanotic (blue) and once blood flow has been restored to them
they turn red. (p. 551)
Suggested Readings
Herbert, W. “Punching the Biological Timeclock.” Science News 122 (July 1982).
House, M.A. “Cocaine.” American Journal of Nursing 90 (Apr. 1990): 40–45.
Kalin, N.H. “The Neurobiology of Fear.” Scientific American 268 (May 1993): 94.
Revkin, A. “Hunting Down Huntington’s.” Discover (Dec. 1993): 100.
Simpson, S. “Pain, Pain, Go Away.” Science News 155 (Feb. 1999): 108–110.