1. © 2009 The McGraw-Hill Companies, Inc. All rights reserved
29-1
The Nervous SystemThe Nervous System
PowerPoint® presentation to accompany:
Medical Assisting
Third Edition
Booth, Whicker, Wyman, Pugh, Thompson

2. 29-2
© 2009 The McGraw-Hill Companies, Inc. All rights reserved
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.

3. 29-3
© 2009 The McGraw-Hill Companies, Inc. All rights reserved
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.

4. 29-4
© 2009 The McGraw-Hill Companies, Inc. All rights reserved
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.

5. 29-5
© 2009 The McGraw-Hill Companies, Inc. All rights reserved
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.

6. 29-6
© 2009 The McGraw-Hill Companies, Inc. All rights reserved
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
Disorders are numerous and often
difficult to diagnose and treat

7. 29-7
© 2009 The McGraw-Hill Companies, Inc. All rights reserved
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

8. 29-8
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General Functions (cont.)
 Three types of neurons
 Afferent or sensory nerves
 Sensory information from environment or inside body
to CNS for interpretation
 Efferent or motor nerves
 Impulses from CNS to PNS to allow for movement or
action
 Interneruons
 Interpretive neurons between afferent and efferent
nerves in the CNS

9. 29-9
© 2009 The McGraw-Hill Companies, Inc. All rights reserved
Apply Your Knowledge
Match the following:
___ Somatic nervous system A. Motor nerves
___ Autonomic nervous system B. Governs skeletal or voluntary muscles
___ Afferent nerves C. Governs respiratory and GI systems
___ Efferent nerves D. Go-betweens or interpreters
___ Interneurons E. Sensory nerves
C
A
E
D
B
ANSWER:

10. 29-10
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Neuron Structure
 Functional cells of NS
 Transmit electrochemical
messages called nerve
impulses to
 Other neurons
 Effectors (muscles or
glands)

11. 29-11
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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

12. 29-12
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Neuron Structure (cont.)
Neurons have cell
body processes called
nerve fibers that
extend from the cell
body.
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

13. 29-13
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Neuron Structure (cont.)
 White matter – axons with
myelin sheath
 Schwann cells – neurological cells
 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
Schwann
cells
Axon
Dendrites

14. 29-14
© 2009 The McGraw-Hill Companies, Inc. All rights reserved
Apply Your Knowledge
True or False:
___ Effectors are neurons.
___ Neurons can reproduce.
___ Astrocytes anchor blood vessels to nerve cells.
___ Microglia act as phagocytes.
___ Oligodendrocytes are reproductive cells.
___ Repolarization is the return to the resting state.
F
T
T
F
T
F
ANSWER:
They are the muscles or glands.
Neurons cannot reproduce.
They take part in
myelin production.
GOODJOB!

15. 29-15
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Nerve Impulse
 Membrane potential
 Neuron cell membrane at rest is in a polarized state
 Inside of cell membrane is negative
 Outside of cell membrane is positive due to more Na+
and K+
 As Na+
and K+
move into the cell, the membrane becomes
depolarized
 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

16. 29-16
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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

17. 29-17
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Nerve Impulse (cont.)
 Functions of neurotransmitters
 Cause muscles to contract or relax
 Cause glands to secrete products
 Activate or inhibit neurons

18. 29-18
© 2009 The McGraw-Hill Companies, Inc. All rights reserved
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

19. 29-19
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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

20. 29-20
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CNS (cont.)
 Meninges –protect brain and spinal cord
 Dura mater
 Tough outer layer
 Arachnoid mater
 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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CNS (cont.)
 Epidural space
 Above dura mater
 Subdural space
 Below dura mater
 Subarachnoid space
 Between arachnoid mater and pia mater
 Contains cerebrospinal fluid (CSF)
 Cushions CNS

22. 29-22
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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

23. 29-23
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CNS: Spinal Cord (cont.)
 Cervical enlargement
 Motor neurons that control
muscles of the arms
 Lumbar enlargement
 Motor neurons that control
muscles of the legs

24. 29-24
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 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
matter Spinal
Cord/Nerve
CNS: Spinal Cord (cont.)

25. 29-25
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 White matter
 Outer tissue
 Contains myelinated axons
 Divisions are called columns (funiculi)
 Columns contain groups of axons called nerve
tracts
Spinal
Cord/Nerve
Spinal
Cord/Nerve
CNS: Spinal Cord (cont.)

26. 29-27
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 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
CNS: Spinal Cord (cont.)

27. 29-28
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 Reflexes
 Another function of the spinal cord is to participate in
reflexes
 Reflex – a predictable, automatic response to stimuli
Receptor Sensory Neurons
Effectors Motor Neurons
Interneurons
CNS: Spinal Cord (cont.)

28. 29-29
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CNS: Brain
 Four sections
 Cerebrum
 Diencephalons
 Brain stem
 Cerebellum

29. 29-30
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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

30. 29-31
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 Lobes
 Frontal
 Motor areas for voluntary
body movements
 Parietal
 Somatosensory – interprets
sensations
 Temporal
 Auditory – interprets sounds
 Occipital
 Interprets what a person sees
Frontal Parietal
Occipital
Temporal
CNS: Brain – Cerebrum (cont.)

31. 29-32
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 Cortex
 Outer layer – gray
matter
 Contains about 75%
of all neurons
 Inner layer – white matter
 Functions
 Interpret sensory information
 Initiate body movements
 Stores memories and creates emotions
 Ventricles
 Interconnected
cavities within the
brain
 Filled with CSF
CNS: Brain – Cerebrum (cont.)

32. 29-33
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 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
CNS: Brain – Diencephalon

33. 29-34
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 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
CNS: Brain – Brain Stem

34. 29-35
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 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
CNS: Brain – Cerebellum

35. 29-37
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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

36. 29-38
© 2009 The McGraw-Hill Companies, Inc. All rights reserved
Apply Your Knowledge
Match the following:
___ Meninges A. Carry motor information from brain
___ Ascending tracts B. Stores memories and creates emotions
___ Descending tracts C. Grooves on the surface of the cerebrum
___ Cerebral cortex D. Carry sensory information to the brain
___ Hypothalamus E. Predictable, automatic response to stimuli
___ Sulci F. Maintains homeostasis
___ Cerebellum G. Coordinates skeletal muscle contractions
___ Reflexes H. Protects the brain and spinal cord
B
F
C
G
E
D
A
H
SUPER!

37. 29-39
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Peripheral Nervous System
 Nerves that branch
off the CNS
 Peripheral nerves
 Two types:
 Cranial nerves
 Spinal nerves

38. 29-40
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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.

39. 29-41
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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
PNS: Cranial Nerves (cont.)

40. 29-42
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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
PNS: Cranial Nerves (cont.)

41. 29-43
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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
PNS: Cranial Nerves (cont.)

42. 29-44
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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
PNS: Cranial Nerves (cont.)

43. 29-45
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 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)
 1 pair of coccygeal nerves (C0) Spinal
Nerves
PNS: Spinal Nerves

44. 29-46
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 Dermatome
 Skin segment innervated by spinal nerve
 C1 is not associated with a dermatome
 Ventral root
 Axons of motor neurons only
 Dorsal root
 Axons of sensory neurons only
 Dorsal root ganglion
 Contains cell bodies of sensory neurons
PNS: Spinal Nerves (cont.)

45. 29-47
© 2009 The McGraw-Hill Companies, Inc. All rights reserved
 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
PNS: Spinal Nerves (cont.)

46. 29-49
© 2009 The McGraw-Hill Companies, Inc. All rights reserved
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

47. 29-50
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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

48. 29-51
© 2009 The McGraw-Hill Companies, Inc. All rights reserved
 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
PNS: Autonomic Nervous System (cont.)

49. 29-52
© 2009 The McGraw-Hill Companies, Inc. All rights reserved
 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
PNS: Autonomic Nervous System (cont.)

50. 29-53
© 2009 The McGraw-Hill Companies, Inc. All rights reserved
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.

51. 29-54
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Neurologic Testing
 Typical neurologic examination
 State of consciousness
 Reflex activity
 Speech patterns
 Motor patterns

52. 29-55
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Neurologic Testing: Diagnostic Procedures
 Lumbar puncture
 Magnetic resonance
imaging (MRI)
 Positron emission
tomography (PET) scan
 Cerebral angiography
 Computerized
tomography (CT) scan
 Electroencephalogram
(EEG)
 X-ray

53. 29-56
© 2009 The McGraw-Hill Companies, Inc. All rights reserved
Neurologic Testing – Cranial Nerve Tests
 Olfactory nerves (Cranial nerve I)
 Have patient smell various substances
 Cranial nerves III, IV, and VI
 Have patient track movement of finger
 Cranial nerve V
 Have patient clench teeth, feel jaw muscles

54. 29-57
© 2009 The McGraw-Hill Companies, Inc. All rights reserved
 Cranial nerve VII
 Check patient’s facial expression
 Cranial nerve XII
 Have patient extend his tongue and move it from
side to side
Neurologic Testing – Cranial Nerve Tests (cont.)

55. 29-58
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Neurologic Testing: Reflex Testing
 Areflexia
 Absence of a reflex
 Hyporeflexia
 Decreased reflex
 Hyperreflexia
 Stronger-than-normal reflex

56. 29-59
© 2009 The McGraw-Hill Companies, Inc. All rights reserved
 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
Neurologic Testing: Reflex Testing

57. 29-60
© 2009 The McGraw-Hill Companies, Inc. All rights reserved
Apply Your Knowledge
Match the following:
___ State of consciousness A. Determines the health of
peripheral nerves
___ Reflex activity B. Loss of balance, abnormal
posture
___ Speech patterns C. Stupor, delirium, vegetative
___ Motor patterns D. Loss of ability to form words
A
D
B
C
ANSWER:

58. 29-61
© 2009 The McGraw-Hill Companies, Inc. All rights reserved
Common Diseases and Disorders
Disease/Disorder Description
Alzheimer’s
disease
Progressive, degenerative disease of
the brain
Amyotrophic
lateral sclerosis
(ALS)
Lou Gehrig’s disease
Degeneration of neurons in the spinal
cord and brain
Bell’s palsy Weak or paralyzed facial muscles

59. 29-62
© 2009 The McGraw-Hill Companies, Inc. All rights reserved
Common Diseases and Disorders (cont.)
Disease/Disorder Description
Brain tumors and
cancers
Abnormal growths
Can be primary or secondary tumors
Most common – gliomas
Epilepsy and
seizures
Occurs as a result of bursts of
electrical signals that disrupt normal
brain functioning
Guillain-Barré
Syndrome
Body’s immune system attacks the
PNS

60. 29-63
© 2009 The McGraw-Hill Companies, Inc. All rights reserved
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
Common Diseases and Disorders (cont.)

61. 29-64
© 2009 The McGraw-Hill Companies, Inc. All rights reserved
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”
Common Diseases and Disorders (cont.)

62. 29-65
© 2009 The McGraw-Hill Companies, Inc. All rights reserved
Apply Your Knowledge
True or false:
___ Alzheimer’s disease is a progressive degenerative disease of
the brain.
___ Epilepsy is due to degenerative neurons in the spinal cord
and brain.
___ Neuralgias are motor system disorders.
___ Stroke occurs when brain cells die because of inadequate
blood flow.
F
F
T
Due to a burst of electrical signals that disrupt brain function.
They are group of disorders referred to as nerve pain.
T
ANSWER:
Bravo!

63. 29-66
© 2009 The McGraw-Hill Companies, Inc. All rights reserved
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

64. 29-67
© 2009 The McGraw-Hill Companies, Inc. All rights reserved
End of Chapter
Activity of the nervous
system improves the
capacity for activity, just
as exercising a muscle
makes it stronger.”
~ Dr. Ralph Gerard