Chapter 29 the_nervous_system

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

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The Nervous SystemThe Nervous SystemPowerPoint® presentation to accompany:

Medical AssistingThird Edition

Booth, Whicker, Wyman, Pugh, Thompson

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Learning Outcomes29.1 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.

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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.

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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.

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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.

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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

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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

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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

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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:

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Neuron Structure

Functional cells of NS

Transmit electrochemical messages called nerve impulses to Other neurons Effectors (muscles or

glands)

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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

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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

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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

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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.

GOOD JOB!

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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

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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

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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

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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!

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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

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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

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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

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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

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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


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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


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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


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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


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CNS: Brain

Four sections Cerebrum Diencephalons Brain stem Cerebellum

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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

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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

OccipitalTemporal

CNS: Brain – Cerebrum (cont.)

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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.)

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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

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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

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

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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

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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

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___ 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!

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Peripheral Nervous System Nerves that branch

off the CNS

Peripheral nerves Two types:

Cranial nerves Spinal nerves

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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.

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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.)

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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


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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


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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


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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

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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.)

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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.)

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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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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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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.)

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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.)

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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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Neurologic Testing

Typical neurologic examination State of consciousness Reflex activity Speech patterns Motor patterns

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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

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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

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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.)

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Neurologic Testing: Reflex Testing

Areflexia Absence of a reflex

Hyporeflexia Decreased reflex

Hyperreflexia Stronger-than-normal reflex

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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

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___ 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:

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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

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Common Diseases and Disorders (cont.)


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

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HeadachesTension

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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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”


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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!

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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

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End of Chapter

Activity of the nervous system improves the capacity for activity, just as exercising a muscle makes it stronger.”

~ Dr. Ralph Gerard

Chapter 29 the_nervous_system

Health & Medicine

Transcript of Chapter 29 the_nervous_system