Download The Nervous System - Learning on the Loop

29-1
The Nervous System
PowerPoint® presentation to accompany:
Medical Assisting
Third Edition
Booth, Whicker, Wyman, Pugh, Thompson
© 2009 The McGraw-Hill Companies, Inc. All rights reserved
29-2
Learning Outcomes
29.1 Explain the difference between the central
nervous system and the peripheral nervous
system.
29.2 Describe the functions of the nervous system.
29.3 Describe the structure of a neuron.
29.4 Describe the function of a nerve impulse and how
a nerve impulse is created.
© 2009 The McGraw-Hill Companies, Inc. All rights reserved
29-3
Learning Outcomes (cont.)
29.5 Describe the structure and function of a synapse.
29.6 Describe the function of the blood-brain barrier.
29.7 Describe the structure and functions of meninges.
29.8 Describe the structure and functions of the spinal
cord.
© 2009 The McGraw-Hill Companies, Inc. All rights reserved
29-4
Learning Outcomes (cont.)
29.9 Describe the location and function of
cerebrospinal fluid.
29.10 Define reflex and list the parts of a reflex arc.
29.11 List the major divisions of the brain and give the
general functions of each.
29.12 Explain the functions of the cranial and spinal
nerves.
© 2009 The McGraw-Hill Companies, Inc. All rights reserved
29-5
Learning Outcomes (cont.)
29.13 Describe the differences between the somatic
nervous system and autonomic nervous system.
29.14 Explain the two divisions of the autonomic
nervous system.
29.15 Describe the causes, signs and symptoms, and
treatments of various diseases and disorders of
the nervous system.
© 2009 The McGraw-Hill Companies, Inc. All rights reserved
29-6
Introduction

Highly complex system
of two parts

Central nervous
system (CNS)

Peripheral nervous
system (PNS)

Controls all other organ
systems and is
important for
maintaining balance
within those systems
Disorders are numerous and often
difficult to diagnose and treat
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29-7
General Functions of the NS

CNS


Brain
Spinal cord

PNS


Peripheral nerves
Two sections


Somatic nervous system
(SNS)
 Skeletal or voluntary
muscles
Autonomic nervous system
(ANS)
 Automatic functions
© 2009 The McGraw-Hill Companies, Inc. All rights reserved
29-8
General Functions (cont.)

Three types of neurons

Afferent or sensory nerves


Efferent or motor nerves


Sensory information from environment or inside body
to CNS for interpretation
Impulses from CNS to PNS to allow for movement or
action
Interneruons

Interpretive neurons between afferent and efferent
nerves in the CNS
© 2009 The McGraw-Hill Companies, Inc. All rights reserved
29-9
Apply Your Knowledge
Match the following:
ANSWER:
___
B Somatic nervous system
A. Motor nerves
___
C Autonomic nervous system
B. Governs skeletal or voluntary muscles
___
E Afferent nerves
C. Governs respiratory and GI systems
___
A Efferent nerves
D. Go-betweens or interpreters
___
D Interneurons
E. Sensory nerves
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29-10
Neuron Structure

Functional cells of NS

Transmit electrochemical
messages called nerve
impulses to


Other neurons
Effectors (muscles or
glands)
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29-11
Neuron Structure (cont.)

Neurons lose their ability to divide


If destroyed, not replaced
Neuralgia




Support cells for neurons that can divide
Astrocytes – anchor blood vessels to nerves
Microglia – act as phagocytes
Oligodendrocytes – assist with production of
myelin sheath
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29-12
Neuron Structure (cont.)

Neurons have cell
body processes called
nerve fibers that
extend from the cell
body.
Dendrites – short


Receive nerve impulses
for the neuron
Axons – long

Send nerve impulses
away from the cell body
© 2009 The McGraw-Hill Companies, Inc. All rights reserved
29-13
Neuron Structure (cont.)

White matter – axons with
myelin sheath

Dendrites
Schwann cells – neurological cells



Schwann
cells
Axon

Wrap around some axons
Cell membranes contain myelin
Myelin insulates axons and
enables axons to send nerve
impulses more quickly
Gray matter – axons without
myelin sheath
© 2009 The McGraw-Hill Companies, Inc. All rights reserved
29-14
Apply Your Knowledge
True or False:
ANSWER:
___
F Effectors are neurons.
F Neurons can reproduce.
___
They are the muscles or glands.
Neurons cannot reproduce.
T Astrocytes anchor blood vessels to nerve cells.
___
T Microglia act as phagocytes.
___
They take part in
myelin production.
T Repolarization is the return to the resting state.
___
F Oligodendrocytes are reproductive cells.
___
GOOD JOB!
© 2009 The McGraw-Hill Companies, Inc. All rights reserved
29-15
Nerve Impulse

Membrane potential

Neuron cell membrane at rest is in a polarized state



As Na+ and K+ move into the cell, the membrane becomes
depolarized



Inside of cell membrane is negative
Outside of cell membrane is positive due to more Na+ and K+
Inside becomes more positive
Action potential (nerve impulse) is created
Repolarization occurs when K+ and later Na+ move to the
outside of the cell membrane

Return of the cell to polarized (resting) state
© 2009 The McGraw-Hill Companies, Inc. All rights reserved
29-16
Nerve action
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29-17
Nerve Impulse (cont.)

Impulse travels down axon to synaptic knob

Vesicles or small sacs in synaptic knob


Produce chemicals called neurotransmitters
Neurotransmitters are released by synaptic knob

Allow impulse transmission to postsynaptic structures



Dendrites
Cell bodies
Axons of other neurons
© 2009 The McGraw-Hill Companies, Inc. All rights reserved
29-18
Synapse
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29-19
Nerve Impulse (cont.)

Functions of neurotransmitters

Cause muscles to contract or relax

Cause glands to secrete products

Activate or inhibit neurons
© 2009 The McGraw-Hill Companies, Inc. All rights reserved
29-20
Apply Your Knowledge
What is the function of neurotransmitters?
ANSWER: Neurotransmitters cause muscles to
contract or relax, cause glands to secret products,
activate neurons to send nerve impulses, or inhibit
neurons from sending them.
Right!
© 2009 The McGraw-Hill Companies, Inc. All rights reserved
29-21
Central Nervous System


Includes the spinal cord and brain
Blood-brain barrier


Protects layers of the membranes of the CNS
Formed by tight capillaries


Prevents unwanted substances from entering the CNS
tissues
Inflammation can make more permeable
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29-22
CNS (cont.)

Meninges –protect brain and spinal cord

Dura mater


Arachnoid mater


Tough outer layer
Middle layer (web-like)
Pia mater



Innermost and most
delicate
Directly on top of brain
and spinal cord
Holds blood vessels on the
surface of these structures
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29-23
CNS (cont.)

Epidural space


Subdural space


Above dura mater
Below dura mater
Subarachnoid space



Between arachnoid mater and pia mater
Contains cerebrospinal fluid (CSF)
Cushions CNS
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29-24
CNS: Spinal Cord

Slender structure continuous with the
brain

Descends into the vertebral canal and
ends around the level of the first or
second lumbar vertebra

31 spinal segments:





8 cervical segments
12 thoracic segments
5 lumbar segments
5 sacral segments
1 coccygeal segment
© 2009 The McGraw-Hill Companies, Inc. All rights reserved
29-25
CNS: Spinal Cord (cont.)

Cervical enlargement


Motor neurons that control
muscles of the arms
Lumbar enlargement

Motor neurons that control
muscles of the legs
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29-26
CNS: Spinal Cord (cont.)

Gray matter

Inner tissue with darker color

Contains neuron cell bodies and their dendrites

Divisions are called horns

Central canal runs down the entire length of the
spinal cord through the center of the gray
Spinal
matter
Cord/Nerve
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29-27
CNS: Spinal Cord (cont.)

White matter

Outer tissue

Contains myelinated axons

Divisions are called columns (funiculi)

Columns contain groups of axons called nerve
tracts
Spinal
Cord/Nerve
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29-29
CNS: Spinal Cord (cont.)

One function of the spinal cord is to carry sensory
information to and from the brain

Ascending tracts


Carry sensory information up to the brain
Descending tracts

Carry motor information down from the brain to muscles
and glands
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29-30
CNS: Spinal Cord (cont.)

Reflexes


Another function of the spinal cord is to participate in
reflexes
Reflex – a predictable, automatic response to stimuli
Receptor
Sensory Neurons
Interneurons
Effectors
Motor Neurons
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29-31
CNS: Brain

Four sections




Cerebrum
Diencephalons
Brain stem
Cerebellum
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29-32
CNS: Brain – Cerebrum


Largest section
Two cerebral hemispheres




Connected by a thick bundle of nerve fibers
called the corpus callosum
Longitudinal fissure between hemispheres
Sulci – grooves on surface
Gyri or convolutions – bumps of brain matter
between sulci
Brain
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29-33
CNS: Brain – Cerebrum (cont.)

Lobes

Frontal


Motor areas for voluntary
body movements
Somatosensory – interprets
sensations
Temporal


Parietal
Parietal


Frontal
Auditory – interprets sounds
Occipital

Temporal
Occipital
Interprets what a person sees
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29-34
CNS: Brain – Cerebrum (cont.)

Cortex

Outer layer – gray
matter







Interconnected
cavities within the
brain

Filled with CSF
Contains about 75%
of all neurons
Inner layer – white matter
Functions

Ventricles
Interpret sensory information
Initiate body movements
Stores memories and creates emotions
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29-35
CNS: Brain – Diencephalon

Between the cerebral hemispheres superior to
the brain stem

Thalamus


Relay station for sensory information going to the
cerebral cortex for interpretation
Hypothalamus

Maintains homeostasis by regulating vital
activities
Brain
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29-36
CNS: Brain – Brain Stem


Connects the cerebrum to
the spinal cord
Midbrain



Just beneath
diencephalon
Controls both visual
and auditory reflexes
Pons



Rounded bulge on
underside of brain stem
Between midbrain and
medulla oblongata
Regulates respiration

Medulla oblongata



Inferior portion of brain
stem
Directly connected to spinal
cord
Controls many vital
activities, such as heart rate,
blood pressure, and
breathing
Brain
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29-37
CNS: Brain – Cerebellum

Location



Inferior to the occipital lobes of the cerebrum
Posterior to the pons and medulla oblongata
Coordinates


Complex skeletal muscle contractions that are
needed for body movements
Fine movements
Brain
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29-39
Preventing Brain and Spinal Cord
Injuries

Wear appropriate
protective gear for
sports

Avoid diving into
unknown waters

Always wear seat belts

Follow safety rules on
playgrounds

Children should be in
car seats appropriate
for age and weight

Know how to get help
quickly in emergencies

Follow traffic rules and
signs while walking,
biking, or driving
© 2009 The McGraw-Hill Companies, Inc. All rights reserved
29-40
Apply Your Knowledge
SUPER!
Match the following:
___
H Meninges
A. Carry motor information from brain
___
D Ascending tracts
B. Stores memories and creates emotions
___
A Descending tracts
C. Grooves on the surface of the cerebrum
___
B Cerebral cortex
D. Carry sensory information to the brain
___
F Hypothalamus
E. Predictable, automatic response to stimuli
___
C Sulci
F. Maintains homeostasis
___
G Cerebellum
G. Coordinates skeletal muscle contractions
___
E Reflexes
H. Protects the brain and spinal cord
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29-41
Peripheral Nervous System

Nerves that branch
off the CNS

Peripheral nerves

Two types:
 Cranial nerves
 Spinal nerves
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29-42
PNS: Cranial Nerves
I.
Olfactory nerves

Carry smell information to the brain for interpretation
II. Optic nerves

Carry visual information to the brain for interpretation
III. Oculomotor nerves

Found within the muscles that move the eyeball, eyelid,
and iris
IV. Trochlear nerves

Act in the muscles that move the eyeball.
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29-43
PNS: Cranial Nerves (cont.)
V. Trigeminal nerves


Carry sensory information from the surface of the
eye, the scalp, facial skin, the lining of the gums,
and the palate to the brain for interpretation
Also found within the muscles needed for
chewing
VI. Abducens nerves

Act in the muscles that move the eyeball
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29-44
PNS: Cranial Nerves (cont.)
VII. Facial nerves


Found in the muscles of facial expression as
well as in the salivary and tear glands
Also carry sensory information from the
tongue
VIII. Vestibulocochlear nerves

Carry hearing and equilibrium information
from the inner ear to the brain for
interpretation
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29-45
PNS: Cranial Nerves (cont.)
IX. Glossopharyngeal nerves


Carry sensory information from the throat and
tongue to the brain for interpretation
Also act in the muscles of the throat
X. Vagus nerves


Carry sensory information from the thoracic and
abdominal organs to the brain for interpretation
Also found within the muscles in the throat,
stomach, intestines, and heart
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29-46
PNS: Cranial Nerves (cont.)
XI. Accessory nerves

Found within the muscles of the throat, neck,
back, and voice box
XII. Hypoglossal nerves

Found within the muscles of the tongue
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29-47
PNS: Spinal Nerves


Peripheral nerves originating from the spinal
cord
31 pairs of spinal nerves





8 pairs of cervical nerves (C1 through C8)
12 pairs of thoracic nerves (T1 through T12)
5 pairs of lumbar nerves (L1 through L5)
5 pairs of sacral nerves (S1 through S5)
Spinal
1 pair of coccygeal nerves (C0)
Nerves
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29-48
PNS: Spinal Nerves (cont.)

Dermatome



Ventral root


Skin segment innervated by spinal nerve
C1 is not associated with a dermatome
Axons of motor neurons only
Dorsal root


Axons of sensory neurons only
Dorsal root ganglion

Contains cell bodies of sensory neurons
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29-49
PNS: Spinal Nerves (cont.)

Main portions of spinal nerves fuse to form
nerve plexuses

Cervical – supply skin and muscles of neck

Phrenic nerve originates from this plexus



Controls diaphragm
Brachial – control muscles in the arms
Lumbosacral – lower abdomen, external genitalia,
buttocks, thighs, legs, and feet

Sciatic nerve originates from this plexus

Controls muscles of legs
Spinal
Nerves
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29-51
PNS: Somatic Nervous System


Nerves that connect the CNS to skin and skeletal
muscle
“Voluntary” nervous system

Controls skeletal muscles, which are under voluntary
control
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29-52
PNS: Autonomic Nervous System



Nerves that connect the CNS to organs and other
structures
“Involuntary” nervous system
Motor neurons located in ganglia

Neuron cell bodies outside the CNS
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29-53
PNS: Autonomic Nervous System (cont.)

Sympathetic division


“Fight or flight” – Prepares body for stressful or
emergency situations
Neurons release neurotransmitter norepinephrine




Increases heart and breathing rates
Slows down muscles of the stomach and intestines
Dilates pupils
Constricts blood vessels – increases blood pressure
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29-54
PNS: Autonomic Nervous System (cont.)

Parasympathetic division



Prepares body for rest and digesting
Controls most of the body’s organs
Releases acetylcholine





Slows heart and breathing rates
Constricts pupils
Activates muscles of stomach and intestine
No communication with blood vessels
Sympathetic and parasympathetic divisions
are antagonistic
© 2009 The McGraw-Hill Companies, Inc. All rights reserved
29-55
Apply Your Knowledge
What is the difference between the sympathetic and
parasympathetic nervous systems?
ANSWER: The sympathetic nervous system prepares the
body for stress. It releases norepinephrine, causing an
increase in heart and respiratory rate, slows down the GI
system, and dilates pupils. The sympathetic system also
controls constriction of blood vessels.
The parasympathetic system prepares the body for resting
and digesting. It releases acetylcholine, which slows heart
and respiratory rate, constricts pupils and stimulates the GI
system. It has no effect on most blood vessels.
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29-56
Neurologic Testing

Typical neurologic examination




State of consciousness
Reflex activity
Speech patterns
Motor patterns
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29-57
Neurologic Testing: Diagnostic Procedures

Lumbar puncture

Computerized
tomography (CT) scan

Magnetic resonance
imaging (MRI)

Electroencephalogram
(EEG)
Positron emission
tomography (PET) scan

X-ray


Cerebral angiography
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29-58
Neurologic Testing – Cranial Nerve Tests

Olfactory nerves (Cranial nerve I)


Cranial nerves III, IV, and VI


Have patient smell various substances
Have patient track movement of finger
Cranial nerve V

Have patient clench teeth, feel jaw muscles
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29-59
Neurologic Testing – Cranial Nerve Tests (cont.)

Cranial nerve VII


Check patient’s facial expression
Cranial nerve XII

Have patient extend his tongue and move it from
side to side
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29-60
Neurologic Testing: Reflex Testing

Areflexia


Hyporeflexia


Absence of a reflex
Decreased reflex
Hyperreflexia

Stronger-than-normal reflex
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29-61
Neurologic Testing: Reflex Testing

Biceps reflex


Absence indicates spinal cord damage in the
cervical region
Knee reflex

Absence may indicate damage to lumbar or
femoral nerves
 Abdominal

reflexes
Used to evaluate damage to thoracic spinal nerves
© 2009 The McGraw-Hill Companies, Inc. All rights reserved
29-62
Apply Your Knowledge
Match the following:
ANSWER:
C State of consciousness
___
A Reflex activity
___
D Speech patterns
___
B Motor patterns
___
A. Determines the health of
peripheral nerves
B. Loss of balance, abnormal
posture
C. Stupor, delirium, vegetative
D. Loss of ability to form words
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29-63
Common Diseases and Disorders
Disease/Disorder Description
Alzheimer’s
disease
Amyotrophic
lateral sclerosis
(ALS)
Bell’s palsy
Progressive, degenerative disease of
the brain
Lou Gehrig’s disease
Degeneration of neurons in the spinal
cord and brain
Weak or paralyzed facial muscles
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29-64
Common Diseases and Disorders (cont.)
Disease/Disorder Description
Brain tumors and Abnormal growths
cancers
Can be primary or secondary tumors
Most common – gliomas
Epilepsy and
Occurs as a result of bursts of
seizures
electrical signals that disrupt normal
brain functioning
Guillain-Barré
Syndrome
Body’s immune system attacks the
PNS
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29-65
Common Diseases and Disorders (cont.)
Disease/Disorder Description
Headaches
Tension
Migraines
Cluster
Episodic or chronic
With aura/without aura
Form of migraines; occurs in groups
Meningitis
Inflammation of meninges
Multiple
sclerosis (MS)
Chronic disease of CNS
Myelin is destroyed
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29-66
Common Diseases and Disorders (cont.)
Disease/Disorder Description
Neuralgias
Disorders causing nerve pain
Parkinson’s
disease
Progressive and degenerative motor
system disorder
Sciatica
Damage to sciatic nerve
Stroke
Brain cells die because of an
inadequate blood flow; “brain attack”
© 2009 The McGraw-Hill Companies, Inc. All rights reserved
29-67
Apply Your Knowledge
True or false:
Bravo!
ANSWER:
T Alzheimer’s disease is a progressive degenerative disease of
___
the brain.
F Epilepsy is due to degenerative neurons in the spinal cord
___
and brain.
Due to a burst of electrical signals that disrupt brain function.
F Neuralgias are motor system disorders.
___
They are group of disorders referred to as nerve pain.
T Stroke occurs when brain cells die because of inadequate
___
blood flow.
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29-68
In Summary

Functions of the nervous system





Detecting and interpreting sensory information
Making decision about that information
Responding to and carrying out motor functions
Neurons are responsible for functions
Divisions


CNS – brain and spinal cord
PNS – cranial and spinal nerves
Knowledge of this system is essential when assisting the
physician during a neurologic exam
© 2009 The McGraw-Hill Companies, Inc. All rights reserved
29-69
End of Chapter
Activity of the nervous
system improves the
capacity for activity, just
as exercising a muscle
makes it stronger.”
~ Dr. Ralph Gerard
© 2009 The McGraw-Hill Companies, Inc. All rights reserved