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CHAPTER 19
NERVOUS SYSTEM
Copyright © 2012, 2007, 2003, 1997, 1991 by Mosby, Inc., an affiliate of Elsevier Inc.
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Chapter 19 Learning Objectives

Define at least 10 terms relating to the
nervous system.

Describe the function of the nervous system.

Identify at least 10 structures of the nervous
system.
Copyright © 2012, 2007, 2003, 1997, 1991 by Mosby, Inc., an affiliate of Elsevier Inc.
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Chapter 19 Learning Objectives

Identify at least three methods used to assess
the function of the nervous system.

Describe at least five disorders of the nervous
system.
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Structure and Function

The nervous system is divided into two major
parts:

Central nervous system (CNS)
 Peripheral nervous system (PNS)

The nervous system senses, interprets, and
responds to internal and external
environmental changes to maintain the
body’s homeostasis.
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Central Nervous System

Parts of the CNS




Brain
Spinal cord
Coordinates body’s full nervous system
Contains nerves that control connections
between impulses to and from the brain and
the rest of the body
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Central Nervous System

The CNS plays a critical role in maintaining a
healthy, normally functioning body.

Meninges (tough membranes) protect the
nervous tissues.
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Central Nervous System
FIGURE 19-1 Divisions of the nervous system. A, The central nervous system. (From
Sorrentino SA: Mosby’s textbook for nursing assistants, ed 7, St. Louis, 2008, Mosby.)
Copyright © 2012, 2007, 2003, 1997, 1991 by Mosby, Inc., an affiliate of Elsevier Inc.
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Peripheral Nervous System

The PNS contains

12 pairs of cranial nerves
• Originate in the brain

31 pairs of spinal nerves
• Act independently from the brain in some reflex
reactions
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Peripheral Nervous System
FIGURE 19-1 Divisions of the nervous system. B, The peripheral nervous system. (From
Sorrentino SA: Mosby’s textbook for nursing assistants, ed 7, St. Louis, 2008, Mosby.)
Copyright © 2012, 2007, 2003, 1997, 1991 by Mosby, Inc., an affiliate of Elsevier Inc.
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Functions of the
Peripheral Nervous System
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Organs of the
Peripheral Nervous System

PNS organs contain

Afferent (sensory) neurons
• Carry messages from the sensory cell of the body
to the brain

Efferent (motor) neurons
• Carry messages from the brain to the body organs
or parts
• Classified as somatic (voluntary) or automatic
(involuntary)
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Divisions of the Nervous System
FIGURE 19-5 The nervous system may be divided into parts on the basis of their functions.
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Spinal Reflex Arc
FIGURE 19-3 The spinal reflex arc. The motor response to injury is a reflex action
controlled by the spinal nerves.
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Neurons

The basic structural unit of the nervous
system is the nerve.



A nerve is a bundle of fibers that carries impulses
(messages) to and from the body’s organs.
Nerve fibers consist of neurons (cells).
Three main types of neurons
• Afferent (sensory)
• Efferent (motor)
• Interneuron
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Autonomic Nervous System

Sympathetic system

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Sympathetic nerves are stimulated in situations
that require action (e.g., fight-or-flight reaction).
Parasympathetic system

Parasympathetic nerves respond to normal,
everyday situations.
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Neurons

Important parts of a neuron



Dendrites
• Receive impulses and transmits them to the cell body
Cell body
• Transmits impulses to the axon
Axon
• Transmits impulse away from the cell body to the
dendrite of the next neuron

Myelin (white matter)
• White, fatty substance covering the axon
• Arranged in bundles called Schwann cells
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Neurons
FIGURE 19-6 Neuron.
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Glia


Special nervous tissue cells that act as “glue”
to support, bind, repair, and protect neurons
Five major types

Astrocyte cells
 Oligodendroglia
 Microglia
 Ependymal cells
 Neuroglia
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Synapse



Space between two neurons
Impulses from one neuron are transmitted
across the synapse to another neuron by a
chemical called a neurotransmitter.
Most common neurotransmitters


Acetylcholine
Norepinephrine
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Ganglia



Groups of nerve cell bodies
Located outside of the CNS
Increased ability to transmit impulses
because they are clustered in the ganglion
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Plexus and Dermatome
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Plexus
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Four major networks of interwoven spinal nerves
•
•
•
•


Cervical
Brachial
Lumbar
Sacral
Provides impulses to specific regions of the body
Dermatomes

Spinal nerves that control sensations on the skin
surface
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Brain



Largest structure of the nervous system and
one of the largest organs of the body
Weighs 2 to 3 pounds
Covered by three layers of membranes called
meninges



Dura mater
Arachnoid
Pia mater
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The Brain
FIGURE 19-8 The parts of the brain. (From Patton KT, Thibodeau GA: Anatomy & physiology, ed
7, St. Louis, 2010, Mosby.)
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Parts of the Brain
FIGURE 19-8 The parts of the brain. (From Patton KT, Thibodeau GA: Anatomy & physiology, ed
7, St. Louis, 2010, Mosby.)
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Functions of the Brain
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Assessment Techniques

Evaluation of the nervous system includes
assessment of the following:

Mental status
 Cranial nerve function
 Motor and sensory nerve function
 Reflexes
 Coordination
 Gait (walking)
 Balance
 Internal body processes
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Assessment Techniques
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Electroencephalography (EEG)
Lumbar puncture
Myelography
Nerve conduction velocity
Computed tomography (CT)
Positron emission tomography (PET)
Magnetic resonance imaging (MRI)
Magnetic resonance angiography (MRA)
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Electroencephalogram
Showing Waves
FIGURE 19-9 A, Electroencephalogram showing wave types. (From Thibodeau
GA, Patton KT: Human body in health and disease, ed 5, St Louis, 2010, Mosby.)
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Scalp Electrodes
FIGURE 19-9 B, Scalp electrodes detect electrical voltage changes in the cranium. (From
Thibodeau GA, Patton KT: Human body in health and disease, ed 5, St Louis, 2010, Mosby.)
Copyright © 2012, 2007, 2003, 1997, 1991 by Mosby, Inc., an affiliate of Elsevier Inc.
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Magnetic Resonance Imaging
FIGURE 19-10 Magnetic resonance imagery allows the visualization of the body without
use of radiation. (From Elkin MK, et al: Nursing intervention and clinical skills, ed 4, St.
Louis, 2008, Mosby.)
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Disorders of the Nervous System
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Alzheimer’s disease
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Cerebrovascular accident (CVA)
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Form of senile dementia
Commonly called a stroke, it is caused by loss of
oxygen to an area of the brain when a clot blocks
a vessel or when a vessel breaks.
Down syndrome

Genetic disorder caused by the presence of an
extra chromosome
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Warning Signs of Alzheimer’s
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Disorders of the Nervous System

Encephalitis
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Guillain-Barré syndrome


Inflammation of the brain caused by a viral or
bacterial infection or by a chemical agent
Also called infectious polyneuritis, it may appear
shortly after a viral immunization or infection
Headache

The muscles around the occipital area of the brain
constrict the blood flow to the area.
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33
Disorders of the Nervous System

Migraine headaches



Sinus headaches


Vascular headaches of unknown cause
Pain results from narrowing of blood vessels in the
brain
Caused by swelling of the membranes that line the
sinus cavities
Head injury

Occurs when the brain impacts the skull as a
result of a blow or rapid movement
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Disorders of the Nervous System
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Huntington’s chorea
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Degenerative neural disorder that affects brain
tissues
Hydrocephalus
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More cerebrospinal fluid is produced than is
absorbed into the circulatory system.
 Excess fluid increases intracranial pressure and
may enlarge the head.

Intracranial tumors

Usually involve neuroglia, blood vessels, or
membranes rather than neurons
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35
Disorders of the Nervous System
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Meningitis
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Meningocele
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Serious inflammation of the meninges caused by a
bacterium, virus, or fungus
Birth defect that occurs when the membranes
covering the brain or spinal cord protrude through
a congenital defect in the skull or spinal column
Multiple sclerosis

Defect in electrical transmission of the neurons
caused by degeneration of the myelin sheath
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36
Disorders of the Nervous System
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Neural tube defect
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Neurofibromatosis
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Abnormal formation of the skull and spinal column
Defect in an autosomal dominant gene
Parkinson’s disease

Degeneration of certain brain cells
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Tumors of Nervous System Tissue
FIGURE 19-12 Tumors of nervous system tissue develop with neurofibromatosis. (From
Patton KT, Thibodeau GA: Anatomy & physiology, ed 7, St. Louis, 2010, Mosby.)
Copyright © 2012, 2007, 2003, 1997, 1991 by Mosby, Inc., an affiliate of Elsevier Inc.
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Signs of Parkinsonism
FIGURE 19-13 The signs of Parkinsonism include rigidity and
trembling of the head and extremities. (From Thibodeau GA, Patton
KT: Human body in health and disease, ed 4, St Louis, 2005, Mosby.)
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Disorders of the Nervous System
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Poliomyelitis
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Sciatica
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Caused by a virus that spreads from the nose and
throat to neural tissue
Usually a ruptured intervertebral disk and
osteoarthritis, producing pressure on the nerve or
other nerve injury
Seizure

Results from injury, infection, or epilepsy
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Disorders of the Nervous System
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Spina bifida
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Birth defect involving a malformed spinal column
resulting from neural tube defects
Spinal cord injuries


Trauma occurring in the cervical and lumbar area
of the spinal column
Transient ischemic attack (TIA)
 Decreased blood supply to an area of the brain
resulting from a small clot that temporarily lodges
in a vessel
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41
Disorders of the Nervous System

Trigeminal neuralgia
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Sudden, intense, unpredictable pain on one side
of the face caused by pressure on or deterioration
of the trigeminal facial nerve
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Trigeminal Neuralgia
FIGURE 19-14 One method used to relieve the pain of trigeminal neuralgia
is surgically to remove the ganglion on the end of the nerve. (From Patton
KT, Thibodeau GA: Anatomy & physiology, ed 7, St. Louis, 2010, Mosby.)
Copyright © 2012, 2007, 2003, 1997, 1991 by Mosby, Inc., an affiliate of Elsevier Inc.
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Issues and Innovations

Memory research

Memories are retained differently and in different
parts of the brain.
 Ribonucleic acid (RNA) may play a role in storing
and recalling information.
 Most memory research uses a marine slug called
Aplysia or people who have sustained neurologic
loss
• Slugs are used because their ganglia are large and their
behavior pattern is limited.

Computer networks are being designed to
simulate actions of the brain.
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Issues and Innovations

Correction of Parkinson’s disease
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

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Transplantation of adrenal cells to stimulate
production of dopamine
Fetal tissue research
Deep brain stimulation
Autologous neural stem cell transplantation
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45
Summary

The function of the nervous system is to
sense, interpret, and respond to internal and
external environmental changes to maintain
homeostasis.

Structures of the nervous system include the
CNS and PNS and their parts.
Copyright © 2012, 2007, 2003, 1997, 1991 by Mosby, Inc., an affiliate of Elsevier Inc.
46
Summary

Methods of assessment of the nervous
system

EEG
 Lumbar puncture
 Myelography
 CT
 PET
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47