Chapter 7 The Nervous System
Chapter Objectives
Upon completion of this chapter the participant will be able to:
1.
2.
3.
4.
5.
6.
7.
8.
9.
Name the divisions of the nervous system.
Describe the major functions of the nervous system.
Discuss the function of the nerve cell.
Label a diagram of the nerve cell and the brain.
Discuss the function of the various divisions of the brain.
List the protective coverings of the brain.
Discuss the function of the spinal cord.
Analyze, define, spell and pronounce the common terms associated with the
nervous system.
Successfully complete the exercises at the end of the chapter.
The nervous system allows the body to adjust to the requirements of both the inside
and outside of our bodies. As soon as a change in either environment is detected the
brain is notified and it decides what would be the appropriate response and then brings
about that change. This may sound simple but in actual fact it is a very complex
process. The nervous system is more complex than the most sophisticated computer.
Anatomy and Physiology of the Nervous System
Nerves
The nervous system is made up of nervous tissue that consists of bundles of fibers that
carry impulses throughout the body. The root word for nerve is neur/i or neur/o. There
are two different types of nerve cells that are found in the nervous system:
 neurons: carry nerve impulses back and forth through the body
 neuroglia: found between the neurons and act as a protection for the neuron.
Neuron
Neurons are made up of three main parts, each with a very distinct role. These parts
are:
 Cell Body: Contains all the structures that maintain the cell.
 Dendrites: Root like structures that receive impulses and conduct them toward
the cell body. The root for dendrites is dendr/o.
 Axon:
Extends away from the cell body and conducts the impulse away
from the nerve body. Some axons are protected by a white fatty substance
called myelin. The root for axon is axo/.
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Dendrite
Nucleus
Cell body
Axon
Myelin bead
Myelin sheath
Direction of
Impulse Flow
The nervous system is divided into three major structures:
 Central Nervous System: Consists of the brain and spinal cord which is
protected by fluid and a series of membranes. Protection from trauma in the
environment is obtained by the skull and the bones of the vertebrae. The brain
is the information processing area and the spinal cord is the body’s information
super-highway.
 Peripheral Nervous System: Consists of cranial nerves which extend from the
brain, and spinal nerves which come from the spinal cord.
 Autonomic Nervous System: Consists of ganglia on either side of the spinal
cord. Nerves of the autonomic nervous system control involuntary actions of the
body which we are not able to control; e.g. heart rate, breathing.
Impulse Transmission
In order for the nervous system to carry on its many functions there must be
transmission of messages back and forth from one part of the body to another. The
nerves allow for this and the process occurs smoothly with the help of
neurotransmitters. Neurotransmitters are chemical substances that make it possible
for the impulse to jump from one nerve cell to another. We know of at least 40
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neurotransmitters in the body, each with a very specific function. The space between
the nerve cells is referred to as the synapse. An impulse will travel down a neuron to a
synapse and then a neurotransmitter is released that allows the impulse to jump to the
next neuron.
Central Nervous System
The Central Nervous System is made up of the brain and spinal cord. The root for
brain is either encephal/o or cerebr/o. The root for spine is spin/o and for spinal cord
is myel/o. The brain which is encased in the skull is made up of the following parts:
 Cerebrum: The largest part of the brain which receives impulses from all areas
of the body. It is the area of the brain that holds our intellectual ability. The
cerebrum is divided into two hemispheres by a gap that extends down the middle
of the tissue. These two areas are connected by bundles of nerves that allow
the two hemispheres to function together. If for some reason the hemispheres
become spilt each can function independently but there isn’t the integration of
functions that normally occurs.
The outer layer of the cerebrum is a thin gray layer called the cerebral cortex.
The cerebrum is involved in sensory and motor function as well as thought,
judgment and our perception.
Each of the two hemispheres of the brain is divided into lobes: frontal lobe,
parietal lobe, temporal lobe and occipital lobe.
 Thalamus: The thalamus acts as a relay station for impulses coming into the
brain. This area is responsible for detection of touch, temperature and pain.
The root for thalamus is thalam/o.
 Hypothalamus: Located below the thalamus. It helps regulate the functions of
the autonomic nervous system. It helps regulate appetite, thirst, temperature,
sleep cycles and the amount of water retained by the body.
 Brain Stem: This area is sometimes referred to as the “animal brain” because it
is the site of the basic life functions of breathing, heart beat, blood pressure,
ability to see and ability to hear. It is also responsible for the responses of
coughing, sneezing and swallowing.
 Cerebellum: Lies just below the occipital lobe of the cerebrum. It is responsible
for balance, coordination and equilibrium. Root for cerebellum is cerebell/o.
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Parietal Lobe
Skull
Dura Mater
Arachnoid Mater
Frontal Lobe
Pia Mater
Temporal Lobe
Brain Stem
Hypothalamus
s
Thalamus
Cerebellum
Spinal Cord
The human brain weights a mere three pounds and looks like a gray, unshelled walnut,
yet it is the most complex structure in our world and the body's most vital organ. It
encases some 100 billion or more nerve cells, and is capable of sending signals to
thousands of other cells at speeds of more than 200 miles an hour. It defines who we
are, yet is influenced by what we do. It holds the secrets to conditions that have
perplexed mankind for centuries.
Protection for the Brain
 Skull:
The bones that make up our skull protect the brain tissue from
external trauma. The root for skull is crani/o.
 Meninges:
A series of three membranes that cover the brain tissue. The root
for meninges is mening/o and meningi/o. The three membranes
are the dura mater, arachnoid mater and pia mater. In the space
below the arachnoid mater and above the pia mater (subarachnoid)
there is a fluid called the cerebrospinal fluid that acts as a
cushion to absorb trauma during a head injury. This fluid absorbs a
great deal of the impact so the brain tissue doesn’t become
bruised.
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 Blood-Brain Barrier:
A mechanism that prevents dangerous or toxic substances from
leaving the blood stream and moving into brain tissue. It does
allow necessary substances like oxygen and nutrition to pass
through, into the brain.
Spinal Cord
The spinal cord extends from the base of the brain down the back in a canal referred to
as the spinal canal. The cord consists of nerves that are encased in 31 vertebrae for
protection. The spinal cord branches into 31 pairs of spinal nerves that extend from the
cord to the limbs and lower parts of the body. The root for spinal cord is myel/o. Like
the brain it is protected by the three layers of meninges and the cerebrospinal fluid.
Peripheral Nervous System
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The peripheral nervous system consists of the cranial nerves which extend from the
brain and the spinal nerves which extend from the spinal cord. We have 12 pairs of
cranial nerves and they are named for the area they affect or the function they are
responsible for such areas of the body as the: eyes, face, throat, mouth, tongue, thorax.
There are 31 pairs of spinal nerves, which are generally named for the artery they
accompany or the body part they affect; e.g. the femoral nerve affects the muscles
along the femur.
Autonomic Nervous System
This aspect of the nervous system is divided into two parts; the parasympathetic and
sympathetic. Each division acts as a balancer of the activities of the other. This
allows a state of homeostasis to exist in the body.
The sympathetic system is concerned with preparing the body for emergency/stressful
situations. To prepare you to react quickly in these situations, your breathing rate, heart
rate and blood circulation to the muscles is greatly increased. It also decreases the rate
of your digestion as this is not a necessity in an emergency situation.
The parasympathetic system, in contrast, returns your body to a state of calm after a
stressful situation has passed. It also maintains normal body functions during ordinary
daily circumstances.
Diagnostic Procedures
The most common procedures used to diagnose problems of the nervous system
involve the use of sound and dyes to create graphic pictures. The advances in
technology have allowed for two very specific procedures to be developed: Magnetic
Resonance Imaging (MRI) uses a combination of radio waves and a strong magnetic
field to create images in any part of the body. This procedure is used in diagnosing
brain problems, as well as other problems in the body. The second procedure is the
Computerized Axial Tomography (CAT Scan). During this procedure an X-Ray
beam rotates around the patient and details the structure to be examined at various
depths. The information is then computerized and converted to a picture of that part of
the body.
Pathology of Diseases of the Nervous System
Injuries to the nervous system may be the result of one or a combination of the
following:




Inflammation
Trauma
Decrease in blood circulation to the tissue resulting in death of tissue
Congenital injuries
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Word Parts for the Nervous System
Roots






















ax/o
cephal/o
cerebell/o
cerebr/o, encephal/o
cortic/o
dendr/o
dur/o
encephal/o, cerebr/o
gangli/o, ganglion/o
hydr/o
medull/o
mening/o, meningi/o
myel/o
narc/o
neur/o
noct/i
radicul/o
somn/i, somn/o
spin/o
synaps/o, synapt/o
thalam/o
ventricul/o
axon
head
cerebellum
brain
cortex, outer covering
dendrite
dura mater
brain
ganglion
water
medulla, inner section
meninges, membrane
spinal cord, bone marrow
numbness
nerve
night
nerve root
sleep
spine
synapse
thalamus
ventricles
Suffixes










-algia, -dynia
-cele
-ectomy
-esthesia
-graphy
-kinesia, -kinesis
-oma
-phasia
-plegia
-taxia
pain
hernia, protrusion
removal
sensation, feeling
process of recording, producing images
movement, motion
tumor
speech
paralysis, loss of motor function
order
Prefixes




deechopachysub-
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lack of, removal
sound
thick
below
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Term Analysis and Definition
Word Part
Term
Term Analysis
cerebell/o
cerebellar
cerebell =
cerebellum
-ar = pertaining to
Pertaining to the cerebellum
cerebr/o,
encephal/o
cerebral
cerebr = brain
-al = pertaining to
Pertaining to the brain
cerebrospinal
spin = spine
Pertaining to the brain and
spine
cerebrovascular vascul = vessel
-ar = pertaining to
Definition
Pertaining to the brain and
blood vessels
encephalitis
encephal = brain
-itis = inflammation
Inflammation of the brain
encephalomalacia
-malacia = softening
Softening of the brain
cortical
cortic = cortex, outer
covering
-al= pertaining to
Pertaining to the cortex
corticospinal
spin = spine
Pertaining to the cortex and
spine
epidural
epi = on, upon,
above
dur = dura mater
-al = pertaining to
Pertaining to above the dura
mater
subdural
sub = below, under
Pertaining to under the dura
mater
hydr/o
hydrocephalus
hydr = water
cephal = head
-us = pertaining to
Pertaining to an accumulation
of fluid in the brain
mening/o,
meningi/o
meningitis
mening = meninges,
-itis = inflammation
Inflammation of the meninges
meningoencephalitis
encephal = brain
Inflammation of the meninges
and the brain
myelogram
myel = spinal cord,
bone marrow
-gram = record
Record of the spinal cord
cortic/o
dur/o
myel/o
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Word Part
Term
Term Analysis
Definition
poliomyelitis
-itis = inflammation
polio= gray
Inflammation of the gray matter
of the spinal cord
myoneural
my = muscle
-al = pertaining to
neur = nerve
Pertaining to the muscle and
nerve
neuralgia
-algia = pain
Nerve pain
neurology
-logy = study of
Study of the nervous system
neurologist
-logist = one who
specializes in the
study of
A specialist in the diagnosis
and treatment of nervous
system diseases
neurolysis
-lysis = destruction,
breakdown
Nerve destruction
radicul/o
myeloradiculitis
myel = spinal cord
radicul = nerve root
-itis = inflammation
Inflammation of the spinal cord
and nerve roots.
spin/o
spinal
spin = spinal
-al = pertaining to
Pertaining to the spine
thalam/o
thalamocortical
thalam = thalamus
cortic = cortex
-al = pertaining to
Pertaining to the thalamus and
cerebral cortex
ventricul/o
ventriculostomy ventric = ventricles
neur/o,
neur/i
-stomy = permanent
new opening
Creating a permanentnew
opening into the ventricles
-algia
cephalalgia
cephal = head
-algia = pain
A pain in the head (Headache)
-cele
encephalocele
encephal = brain
-cele = hernia
Hernia of the brain
meningocele
mening = meninges
Hernia of the meninges
myelomeningocele
myel = spinal cord
Hernia of the spinal cord and
meninges
lobectomy
lobe = lobe
-ectomy = surgical
excision
Surgical excision of a lobe of
the brain
-ectomy
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Word Part
-esthesia
-graphy
-kinesia,
-kinesis
-oma
-otomy
Term
Term Analysis
Definition
craniectomy
crani = skull
Surgical removal of a part of
the skull
anesthesia
an = no, not
-esthesia =
sensation
No sensation
hypoesthesia
hypo = below, under
Decreased sensation
hyperesthesia
hyper- excessive,
above
Increased sensation
paresthesia
para = abnormal
Abnormal sensation
cerebral
angiography
cereb = brain
-al = pertaining to
angi = vessel
-graphy = process
of recording
Graphic X-Ray image of the
vessels in the brain..
computerized
axial
tomography
tom/o = to cut
X-Ray beam creates a picture
of various depths of the brain
electroencephalo
-graphy
electr= electric
Process of recording the
electric impulses of the brain
myelography
myel= spinal cord
hyperkinesis
hyper = above,
excessive
-kinesis =
movement
Excessive movement,
hyperactivity
dyskinesia
dys = difficult, bad
-kinesia =
movement
Difficult movement
meningioma
mening = meninges
Tumor of the meninges
myeloma
myel = spinal cord
Tumor of the spinal cord
neurotomy
neur = nerve
-tomy = Surgical
incision
Surgical incision into a nerve
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X-Ray image of the spinal cord
Word Part
-pathy
-phasia
-plegia
Term
Term Analysis
Definition
craniotomy
crani = skull
Creation of an opening into the
skull
encephalopathy
encephal = brain
-pathy = disease
Disease of the brain
neuropathy
neur = nerve
Disease of the nerve
aphasia
a = no, not
phasia = speech
No speech
dysphasia
dys = difficult, bad
Difficult speech
hemiplegia
hemi = half
-plegia = paralysis
Paralysis of either (half) the
right side or left side of the
body
monoplegia
mono = one
Paralysis of one extremity
paraplegia
para = beside, near
Paralysis of the lower part of
the body and legs
Paralysis of all four limbs
quadriplegia
quad = four
-taxia
ataxia
a = no, not
-taxia = order
No muscular coordination
de-
demylination
de- = lack of,
removal
mylin = myelin
sheath
-ion = process
Loss of the myelin sheath.
Vocabulary Words:
Alzheimer’s disease A severe form of senile dementia that may
be due to some defect in the neurotransmitter system. There is
cortical destruction that causes variable degrees of confusion,
memory loss and other cognitive defects.
Anorexia nervosa
A complex psychological disorder in which the individual refuses to
eat or has an aberrant eating pattern
coma
An unconscious state or stupor from which the patient
cannot be aroused
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epilepsy
A disorder of cerebral function resulting from abnormal electrical
activity or malfunctioning of the chemical substances of the brain
herpes zoster
shingles, an acute viral disease characterized by painful
vesicular eruptions along the segment of the spinal or cranial
nerves
paresis
A slight, partial, or incomplete paralysis
Parkinson disease A chronic disease of the nervous system. It is characterized by a
loss of equilibrium and by salivation, frustration, nausea, dryness of
the mouth, and muscular tremors, syncope, and fainting
Abbreviations:
ALS
amyotrophic lateral sclerosis
ANS
autonomic nervous system
CNS
central nervous system
CSF
cerebrospinal fluid
CT
computerized tomography
CVA
cerebrovascular accident
LP
lumbar puncture
MS
multiple sclerosis
PNS
peripheral nervous system
TIA
transient ischemic attack
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