14

The Autonomic Nervous System Student Objectives

ANS Physiology

When you have completed the exercises in this chapter, you will have accomplished the following objectives: Introduction 1. Define the autonomic nervous system and explain its relationship to the peripheral nervous system.

6. Describe the clinical importance of drugs that mimic or inhibit adrenergic or cholinergic effects.

E L

7. State the effects of the parasympathetic and sympathetic divisions on the following organs: heart, blood vessels, gastrointestinal tract, lungs, adrenal medulla, and external genitalia.

P M

2. Compare the somatic and autonomic nervous systems relative to effectors, efferent pathways, and neurotransmitters released.

3. Compare and contrast the general functions of the parasympathetic and sympathetic divisions. ANS Anatomy

5. Define cholinergic and adrenergic fibers, and list the different types of their receptors.

A S

4. For the parasympathetic and sympathetic divisions, describe the site of CNS origin, locations of ganglia, and general fiber pathways.

8. Describe autonomic nervous system controls.

Homeostatic Imbalances of the ANS 9. Explain the relationship of some types of hypertension, Raynaud’s disease, and the mass reflex reaction to disorders of autonomic functioning.

Copyrighted material - all rights reserved. Adapt design for new edition; update, revise, and new composition and line art [email protected]

357

358

Study Guide for Anatomy & Physiology

The autonomic nervous system (ANS) is the involuntary part of the efferent motor division of the peripheral nervous system (PNS). The ANS is structurally and functionally subdivided into sympathetic and parasympathetic divisions. The two divisions innervate cardiac muscle, smooth muscle, and glands in a coordinated and reciprocal manner to maintain homeostasis of the internal environment. In Chapter 14, topics for study include structural and functional comparisons between the somatic and autonomic nervous systems and between the sympathetic and parasympathetic divisions. Also included are exercises on the anatomy and physiology of the ANS and impairments and developmental aspects of the ANS.

E L

BUILDING THE FRAMEWORK

P M

Introduction

1. Identify the following descriptions as characteristic of the somatic nervous system (use S), of the autonomic nervous system (use A), or of both systems (use S, A). Insert your letter responses in the answer blanks.

A S

_______

1. Has efferent motor fibers

_______

2. Single axonal pathway extends from the CNS to each effector

_______

3. Slower conduction of nerve impulses

_______

4. Motor neuron cell bodies are located in the CNS

_______

5. Typically thick, heavily myelinated motor fibers

_______

6. Target organs are skeletal muscles

_______

7. Has preganglionic and ganglionic neurons

_______

8. Effectors are glands and involuntary muscles

_______

9. Neural pathways are found in cranial and spinal nerves

_______ 10. One ganglion of each motor unit is located outside the CNS _______ 11. Typically thin fibers with little or no myelination _______ 12. Effect of neurotransmitter on target organ is always excitatory

Copyrighted material - all rights reserved. Adapt design for new edition; update, revise, and new composition and line art [email protected]

Chapter 14

The Autonomic Nervous System

359

_______ 13. Neurotransmitter at effector site is always acetylcholine _______ 14. No ganglia are present _______ 15. Neurotransmitter effect on target organ may be excitation or inhibition _______ 16. Motor activities under control of higher brain centers 2. Identify, by color coding and coloring, the following structures in Figure 14.1, which depicts the major anatomical differences between the somatic and autonomic motor divisions of the PNS. Also identify by labeling all structures provided with leader lines.



Somatic motor neuron



Effector of the somatic motor neuron



ANS preganglionic neuron



Effector of the autonomic motor neuron



ANS ganglionic neuron



Intrinsic ganglionic cell



Autonomic ganglion



Myelin sheath



Gray matter of spinal cord (CNS)



White matter of spinal cord (CNS)

E L

P M

A S

Figure 14.1

Copyrighted material - all rights reserved. Adapt design for new edition; update, revise, and new composition and line art [email protected]

360

Study Guide for Anatomy & Physiology

ANS Anatomy 1. Figure 14.2 is a highly simplified diagram of the anatomy of the two ANS divisions. Only certain target structures are indicated; for clarity, the spinal cord is depicted twice. Circles represent ganglia, and neural pathways are shown as dotted lines for use as guidelines. Select eight colors; color the coding circles, structures, and specified boxes listed on the facing page. Use solid lines for preganglionic fibers and dashed lines for postganglionic fibers. Next, label each division in the answer blanks below the figure. Then, insert leader lines and label the four cranial nerves by number. 2. The following paragraphs trace the sympathetic and parasympathetic pathways involved in the innervation of selected organs or structures. Complete the statements by inserting the missing terms in the answer blanks. Referring to Figure 14.2 should help you complete this exercise. _________________________

1.

_________________________

2.

_________________________

3.

_________________________

4.

_________________________

5.

_________________________

6.

_________________________

7.

_________________________

8.

_________________________

9.

P M

A S

_________________________ 10. _________________________ 11. _________________________ 12. _________________________ 13. _________________________ 14. _________________________ 15. _________________________ 16.

E L

Sympathetic preganglionic fibers arise from cell bodies located (1) horns of segments ______ (2) of the ______ (3) . These in the ______ (4) rami fibers leave the ventral root by passing through the ______ (5) , which are aligned communicantes and enter adjoining ______ (6) trunk or chain. Synapses of sympathetic to form the ______ fibers may or may not occur in the adjoining ganglia. In cases where synapses are made within the adjoining ganglia, the (7) axons enter the spinal nerves by way of the gray ______ (8) . ______ (9) The term gray means that the axons are ______. Examples of structures with this type of sympathetic innervation are the (10) sweat glands and the ______ __ in blood vessel walls. Some preganglionic axons may travel within the sympathetic trunk to synapse in other than adjoining ganglia. For example, (11) synapses within the superior ______ __ ganglion contribute fibers (12) (13) __ glands, the heart, innervating the ______ __ of the eye, the ______ and the respiratory tract organs. Though some fibers serve the heart, most of the postganglionic fibers issuing from the other (14) two cervical ganglia innervate the ______ __ .

Some fibers enter and leave the sympathetic chain without (15) synapsing. Preganglionic fibers T5 –L2 synapse in ______ __ ganglia located anterior to the vertebral column. For example, fibers (16) __ nerves, which synapse mainly T5 –T12 contribute to the ______ (17) in the ______ __ ganglia. From there, postganglionic fibers distrib(18) ute to serve most of the ______ __ organs. A few fibers pass through the celiac ganglion without synapsing. These fibers (19) (20) __ synapse within the medulla of the ______ __ gland. The ______ (L1 and L2) splanchnic nerves synapse in prevertebral ganglia, (21) from which postganglionic fibers innervate the ______ __ and reproductive organs. (continues on page 362)

_________________________ 17. _________________________ 18.

_________________________ 20.

_________________________ 19.

_________________________ 21.

Copyrighted material - all rights reserved. Adapt design for new edition; update, revise, and new composition and line art [email protected]

Chapter 14



Sites of parasympathetic neurons in the CNS

The Autonomic Nervous System



Terminal ganglia



Boxes specifying organs that are provided only with sympathetic fibers



Sites of sympathetic neurons in the CNS



Sympathetic fibers



Parasympathetic fibers



Sympathetic trunk of paravertebral ganglia



Prevertebral ganglia

E L

P M

A S

division A. _____________________________________

361

division B. _____________________________________ Figure 14.2

Copyrighted material - all rights reserved. Adapt design for new edition; update, revise, and new composition and line art [email protected]

362

Study Guide for Anatomy & Physiology

_________________________ 22. _________________________ 23. _________________________ 24. _________________________ 25. _________________________ 26. _________________________ 27. _________________________ 28. _________________________ 29. _________________________ 30.

Parasympathetic preganglionic neurons are located in the (22) (23) ______ __ and in the ______ __ region of the spinal cord. Pregan(24) glionic axons extend from the CNS to synapse in ______ __ ganglia close to or within target organs. Some examples of cranial outflow are the following. In the ciliary ganglion, pregan(25) glionic fibers traveling with the ______ __ nerve synapse with ganglionic neurons within the orbits. The salivary glands are innervated by parasympathetic fibers that travel with cranial (26) (27) __ . nerves ______ __ and ______ (28) ______ __ nerve fibers account for about 90% of all preganglionic parasympathetic fibers in the body. These fibers enter networks (29) of interlacing nerve fibers called ______ __ , from which arise sev(30) eral branches that serve the organs located in the ______ __ and in (31) (32) __ of the spinal the ______ __ . Preganglionic fibers from the ______ cord synapse with ganglionic neurons in ganglia within the walls of the urinary and reproductive organs and the distal half of the large intestine.

E L

P M

_________________________ 31. _________________________ 32.

3. Characterize each of the following anatomical descriptions as it relates to the sympathetic division (use S), the parasympathetic division (use P), or to both divisions (use S, P). Write the correct letter answers in the answer blanks.

A S

_______

1. Short preganglionic and long postganglionic axons

_______

2. Travel within cranial and sacral nerves

_______

3. Called the thoracolumbar division

_______

4. Long preganglionic and short postganglionic axons

_______

5. No fibers in rami communicantes

_______

6. Called the craniosacral division

_______

7. Ganglia are close to the CNS

_______

8. Minimal branching of preganglionic fibers

_______

9. Terminal ganglia are close to or in the visceral organs served

_______ 10. Gray and white rami communicantes utilized _______ 11. Extensive branching of preganglionic fibers _______ 12. Nearly all fibers are accompanied by sensory afferent fibers

Copyrighted material - all rights reserved. Adapt design for new edition; update, revise, and new composition and line art [email protected]

Chapter 14

The Autonomic Nervous System

ANS Physiology 1. The following table lists general functions of the ANS. Use a check mark (✓) to show which division of the ANS is involved in each function. Function

Sympathetic

Parasympathetic

1. Normally in control 2. “Fight-or-flight” system 3. More specific local control 4. Causes a dry mouth, dilates bronchioles

E L

5. Constricts eye pupils, decreases heart rate 6. Conserves body energy

P M

7. Causes increased blood glucose levels

8. Causes increase in digestive tract mobility

9. Arector pili muscles contract (“goose bumps”)

A S

2. Define cholinergic fibers, and name the two types of cholinergic receptors below. 1. Cholinergic fibers __________________________________________________________________________ 2. Cholinergic receptors ______________________________________________________________________ 3. Define adrenergic fibers, and name the two major classes of adrenergic receptors. 1. Adrenergic fibers ___________________________________________________________________________ 2. Adrenergic receptors _______________________________________________________________________

Copyrighted material - all rights reserved. Adapt design for new edition; update, revise, and new composition and line art [email protected]

363

364

Study Guide for Anatomy & Physiology

4. Using the key choices, select which CNS centers control the autonomic activities listed below. Write the correct letters in the answer blanks.

Key Choices A. Brain stem

B. Cerebral cortex

C. Hypothalamus

D. Spinal cord

_________________________

1. The main integration center of the ANS

_________________________

2. Exerts the most direct control over ANS functioning

_________________________

3. Coordinates blood pressure, water balance, and endocrine activity

_________________________

4. Integrates defecation and micturition reflexes

_________________________

5. Controls some autonomic functioning through meditation

_________________________

6. Regulates heart and respiration rates and gastrointestinal reflexes

_________________________

7. Awareness of autonomic functioning through biofeedback training

_________________________

8. Influences autonomic functioning via limbic system connections

E L

P M

A S

5. The following table lists several physiological conditions. Use a check mark (✓) to show which autonomic division is involved for each condition. Function

Sympathetic

Parasympathetic

1. All neurons secrete acetylcholine

2. Controls secretions of catecholamines 3. Control of reflexes that act in thermoregulation 4. Accelerates metabolism 5. Short-lived control of effectors 6. Postganglionic neurons secrete NE 7. Localized control of effectors; not diffuse

6. Circle the term that does not belong in each of the following groupings. (Note: ACh = acetylcholine; NE = norepinephrine.) 1. Skeletal muscle contraction 2. NE

Cholinergic receptors

Usually stimulatory

3. Beta receptor

Cardiac muscle

Nicotinic receptor Heart rate slows

ACh

NE

Adrenergic receptor NE

Copyrighted material - all rights reserved. Adapt design for new edition; update, revise, and new composition and line art [email protected]

Chapter 14

4. Blood pressure control

Sympathetic tone

The Autonomic Nervous System

Parasympathetic tone

Blood vessels partially constricted 5. Parasympathetic tone 6. External genitalia

Urinary tract Sympathetic tone

Digestive tract

Rapid heart rate

Blood vessels dilate

Penis erection

Homeostatic Imbalances of the ANS 1. If a statement is true, write the letter T in the answer blank. If a statement is false, change the underlined word(s) and write the correct word(s) in the answer blank.

E L

_________________________

1. Most autonomic disorders reflect the abnormal control of adrenal medulla activity.

_________________________

2. The cause of Raynaud’s disease is thought to be intense vasoconstriction in response to exposure to cold or emotional stress.

_________________________

3. To promote vasodilation in the patient with a severe case of Raynaud’s disease, a parasympathectomy is performed.

_________________________

4. Hypertension in the overly stressed patient can be controlled with cholinergic blocker medication.

A S

P M

CHALLENGING YOURSELF

At the Clinic 1. After surgery, patients are often temporarily unable to urinate, and bowel sounds are absent. What division of the ANS is affected by anesthesia?

2. Stress-induced stomach ulcers are due to excessive sympathetic stimulation. For example, one suspected cause of the ulcers is almost total lack of blood flow to the stomach wall. How is this related to sympathetic function?

Copyrighted material - all rights reserved. Adapt design for new edition; update, revise, and new composition and line art [email protected]

365

366

Study Guide for Anatomy & Physiology

3. Mrs. Griswold has been receiving treatment at the clinic for Raynaud’s disease. Lately her symptoms have been getting more pronounced and severe, and her doctor determines that surgery is her only recourse. What surgical procedure will be performed, and what effect is it designed to produce?

4. Which is the more likely side effect of Mrs. Griswold’s surgery—anhidrosis or hyperhidrosis—in the area of concern? (Hidrosis = sweating.)

E L

5. Brian, a young man who was paralyzed from the waist down in an automobile accident, has seen considerable progress in the return of spinal cord reflexes. However, quite unexpectedly, he is brought to the ER because of profuse sweating and involuntary voiding. From what condition is Brian suffering? For what life-threatening complication will the clinical staff be alert?

P M

A S

6. John Ryder, a black male in his mid-40s, has hypertension for which no organic cause can be pinpointed. Which class of autonomic nervous system drugs will most likely be prescribed to manage his condition and why?

7. Roweena Gibson, a high-powered marketing executive, develops a stomach ulcer. She complains of a deep abdominal pain that she cannot quite locate, plus a pain in her abdominal wall. Exactly where on the abdominal wall is the superficial pain most likely to be located? (Doing a little research in Chapter 23 may be helpful here.)

8. Imagine that a mad scientist is seeking to invent a death ray that destroys a person’s ciliary, sphenopalatine, and submandibular ganglia (and nothing else). List all the symptoms that would be apparent in the victim. Would the victim die, or would the scientist have to go back to the laboratory to try again?

Copyrighted material - all rights reserved. Adapt design for new edition; update, revise, and new composition and line art [email protected]

Chapter 14

The Autonomic Nervous System

9. How would a drug that inhibits the parasympathetic nervous system affect a person’s pulse?

Stop and Think 1. Can the autonomic nervous system function properly in the absence of visceral afferent input? Explain your response.

E L

Use the following information for questions 2–6: Stretch receptors in the bladder send impulses along visceral afferent nerve fibers to the sacral region of the spinal cord. Synapses with motor neurons there initiate impulses along visceral efferent fibers that stimulate contraction of the smooth muscle of the bladder wall and relaxation of the smooth muscle (involuntary) sphincter to allow urination.

P M

2. What division of the autonomic nervous system is involved?

A S

3. What sort of neuronal circuit does this exemplify?

4. What nerves carry the impulses?

5. How is urination inhibited consciously?

6. How would this pathway be affected by spinal cord transection above the sacral region?

7. Migraine headaches are caused by constriction followed by dilation of the vessels supplying the brain. The pain is associated with the dilation phase and is apparently related to the high rate of blood flow through these vessels. Some migraine sufferers seek relief through biofeedback, learning to trigger dilation of the vessels in the hand(s). How does this provide relief?

Copyrighted material - all rights reserved. Adapt design for new edition; update, revise, and new composition and line art [email protected]

367

368

Study Guide for Anatomy & Physiology

8. Trace the sympathetic pathway from the spinal cord to the iris of the eye, naming all associated structures, fiber types, and neurotransmitters.

9. Trace the parasympathetic pathway from the brain to the heart, naming all associated structures, fiber types, and neurotransmitters.

E L

COVERING ALL YOUR BASES

Multiple Choice Select the best answer or answers from the choices given.

P M

1. Which of the following is true of the autonomic, but not the somatic, nervous system?

A S

A. Neurotransmitter is acetylcholine B. Axons are myelinated

C. Effectors are muscle cells

3. Which best describes ANS control?

D. Has motor neurons located in ganglia

2. Examination of nerve fibers supplying the rectus femoris muscle reveals an assortment of type A fibers and type C fibers. The type A fibers are known to be somatic motor fibers supplying the skeletal muscle. Which of these is likely to be the function of the type C fibers? A. Parasympathetic innervation to the muscle spindles

A. Completely under control of the cerebral cortex B. Completely under control of the brain stem C. Entirely controls itself D. Major control by the hypothalamus and spinal reflexes

4. Which of the following disorders is (are) related specifically to sympathetic functions? A. Achalasia B. Raynaud’s disease C. Orthostatic hypotension D. Hirschsprung’s disease 5. Adrenal medulla development involves: A. neural crest cells

B. Sympathetic innervation to the muscle spindles

B. nerve growth factor

C. Parasympathetic innervation to the blood vessels

D. parasympathetic preganglionic axons

D. Sympathetic innervation to the blood vessels

C. sympathetic preganglionic axons

6. Orville said he had a heartache because he broke up with his girlfriend and put his hand over his heart on his anterior chest. Staci told him that if his heart really hurt, he could also be pointing somewhere else. Where? A. His left arm

C. His gluteal region

B. His head

D. His abdomen

Copyrighted material - all rights reserved. Adapt design for new edition; update, revise, and new composition and line art [email protected]

Chapter 14

Use the following choices to respond to questions 7–25:

The Autonomic Nervous System

______ 16. Includes otic ganglion

A. sympathetic division

______ 17. Includes celiac ganglion

B. parasympathetic division

______ 18. Contains cholinergic fibers

C. both sympathetic and parasympathetic D. neither sympathetic nor parasympathetic ______

7. Typically has long preganglionic and short postganglionic fibers

______

8. Some fibers utilize gray rami communicantes

______

9. Courses through spinal nerves

369

______ 19. Stimulatory impulses from hypothalamus and/or medulla pass through the thoracic spinal cord to connect to preganglionic neurons ______ 20. Hyperactivity of this division can lead to ischemia (loss of circulation) to various body parts and hypertension

E L

______ 10. Has nicotinic receptors on its ganglionic neurons

______ 21. Affected by beta blockers

______ 11. Has nicotinic receptors on its target cells

______ 22. Hypoactivity of this division would lead to decrease in metabolic rate

______ 12. Has splanchnic nerves

______ 23. Stimulated by the RAS

P M

A S

______ 13. Courses through cranial nerves ______ 14. Originates in cranial nerves

______ 15. Effects enhanced by direct stimulation of a hormonal mechanism

Word Dissection

______ 24. Has widespread, long-lasting effects

______ 25. Sets the tone for the heart

For each of the following word roots, fill in the literal meaning and give an example, using a word found in this chapter. Word root

Translation

Example

1. adren

________________________________

________________________________

2. chales

________________________________

________________________________

3. epinephr

________________________________

________________________________

4. mural

________________________________

________________________________

5. ortho

________________________________

________________________________

6. para

________________________________

________________________________

7. pathos

________________________________

________________________________

8. splanchn

________________________________

________________________________

Copyrighted material - all rights reserved. Adapt design for new edition; update, revise, and new composition and line art • [email protected]