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PowerPoint® Lecture Slide Presentation
by Patty Bostwick-Taylor,
Florence-Darlington Technical College
The Nervous
System
7
PART A
Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings
Functions of the Nervous System
 Sensory input—gathering information
 To monitor changes occurring inside and
outside the body
 Changes = stimuli
 Integration
 To process and interpret sensory input and
decide if action is needed
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Functions of the Nervous System
 Motor output
 A response to integrated stimuli
 The response activates muscles or glands
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Functions of the Nervous System
Figure 7.1
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Structural Classification
of the Nervous System
 Central nervous system (CNS)
 Brain
 Spinal cord
 Peripheral nervous system (PNS)
 Nerves outside the brain and spinal cord
 Spinal nerves
 Cranial nerves
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Functional Classification of
the Peripheral Nervous System
 Sensory (afferent) division
 Nerve fibers that carry information to the
central nervous system
 Motor (efferent) division
 Nerve fibers that carry impulses away from the
central nervous system
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Organization of the Nervous System
Figure 7.2
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Functional Classification of
the Peripheral Nervous System
 Motor (efferent) division (continued)
 Two subdivisions
 Somatic nervous system = voluntary
 Autonomic nervous system = involuntary
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Nervous Tissue: Support Cells
 Support cells in the CNS are grouped together as
“neuroglia”
 Function: to support, insulate, and protect
neurons
 9 glial cells : 1 neuron
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Nervous Tissue: Support Cells
 Astrocytes
 Abundant, star-shaped cells
 Brace neurons
 Form barrier between capillaries and neurons
 Control the chemical environment of
the brain
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Nervous Tissue: Support Cells
Figure 7.3a
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Nervous Tissue: Support Cells
 Microglia
 Spiderlike phagocytes
 Dispose of debris
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Nervous Tissue: Support Cells
Figure 7.3b
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Nervous Tissue: Support Cells
 Ependymal cells
 Line cavities of the brain and spinal cord
 Circulate cerebrospinal fluid
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Nervous Tissue: Support Cells
Figure 7.3c
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Nervous Tissue: Support Cells
 Oligodendrocytes
 Wrap around nerve fibers in the central
nervous system
 Produce myelin sheaths
 Found in the CNS
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Nervous Tissue: Support Cells
Figure 7.3d
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Nervous Tissue: Support Cells
 Satellite cells
 Protect neuron cell bodies
 Schwann cells
 Form myelin sheath in the peripheral nervous
system
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Nervous Tissue: Support Cells
Figure 7.3e
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Nervous Tissue: Neurons
 Neurons = nerve cells
 Cells specialized to transmit messages
 Major regions of neurons
 Cell body—nucleus and metabolic center
of the cell
 Processes—fibers that extend from the
cell body
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Nervous Tissue: Neurons
 Cell body
 Nissl substance
 Specialized rough endoplasmic reticulum
 Neurofibrils
 Intermediate cytoskeleton
 Maintains cell shape
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Nervous Tissue: Neurons
Figure 7.4
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Nervous Tissue: Neurons
 Cell body
 Nucleus
 Large nucleolus
 Processes outside the cell body
 Dendrites—conduct impulses toward the cell
body
 Axons—conduct impulses away from the cell
body
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Nervous Tissue: Neurons
Figure 7.4
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Nervous Tissue: Neurons
 Axons end in axonal terminals
 Axonal terminals contain vesicles with
neurotransmitters
 Axonal terminals are separated from the next
neuron by a gap
 Synaptic cleft—gap between adjacent neurons
 Synapse—junction between nerves
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Nervous Tissue: Neurons
 Myelin sheath—whitish, fatty material covering
axons
 Schwann cells—produce myelin sheaths in jelly
roll–like fashion
 Nodes of Ranvier—gaps in myelin sheath along
the axon
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Nervous Tissue: Neurons
Figure 7.5
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Neuron Cell Body Location
 Most neuron cell bodies are found in the central
nervous system
 Gray matter—cell bodies and unmyelinated
fibers
 Nuclei—clusters of cell bodies within the white
matter of the central nervous system
 Ganglia—collections of cell bodies outside the
central nervous system
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Functional Classification of Neurons
 Sensory (afferent) neurons
 Carry impulses from the sensory receptors to
the CNS
 Cutaneous sense organs
 Proprioceptors—detect stretch or tension
 Motor (efferent) neurons
 Carry impulses from the central nervous
system to viscera, muscles, or glands
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Functional Classification of Neurons
Figure 7.7
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Functional Classification of Neurons
 Interneurons (association neurons)
 Found in neural pathways in the central
nervous system
 Connect sensory and motor neurons
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Neuron Classification
Figure 7.6
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Structural Classification of Neurons
 Multipolar neurons—many extensions from the
cell body
Figure 7.8a
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Structural Classification of Neurons
 Bipolar neurons—one axon and one dendrite
Figure 7.8b
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Structural Classification of Neurons
 Unipolar neurons—have a short single process
leaving the cell body
Figure 7.8c
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Functional Properties of Neurons
 Irritability
 Ability to respond to stimuli
 Conductivity
 Ability to transmit an impulse
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Nerve Impulses
 Resting neuron
 The plasma membrane at rest is polarized
 Fewer positive ions are inside the cell than
outside the cell
 Depolarization
 A stimulus depolarizes the neuron’s
membrane
 A depolarized membrane allows sodium (Na+)
to flow inside the membrane
 The exchange of ions initiates an action potential
in the neuron
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Nerve Impulses
Figure 7.9a–b
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Nerve Impulses
 Action potential
 If the action potential (nerve impulse) starts, it
is propagated over the entire axon
 Impulses travel faster when fibers have a
myelin sheath
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Nerve Impulses
Figure 7.9c–d
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Nerve Impulses
 Repolarization
 Potassium ions rush out of the neuron after
sodium ions rush in, which repolarizes the
membrane
 The sodium-potassium pump, using ATP,
restores the original configuration
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Nerve Impulses
Figure 7.9e–f
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Na+
Na+
K+
K+
3 Additional Na channels open,
K channels are closed; interior of
cell becomes more positive.
4 Na channels close and
50
Membrane potential
(mV)
Na+
K+
2 A stimulus opens some Na
channels; if threshold is reached,
action potential is triggered.
Sodium
channel
Na+
Action
potential
3
0
4
2
5 The K channels
–50 Threshold
1
–100
Potassium
channel
inactivate. K channels
open, and K rushes
out; interior of cell more
negative than outside.
Resting potential
5
close relatively
slowly, causing a
brief undershoot.
1
Time (msec)
Na+
Neuron
interior
K+
Neuron
interior
Plasma
membrane
1 Resting state: voltage-gated Na
K+
and K
channels closed; resting
potential is maintained.
1
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43
Return to resting state.
Transmission of a Signal at Synapses
 Impulses are able to cross the synapse to another
nerve
 Neurotransmitter is released from a nerve’s
axon terminal
 The dendrite of the next neuron has receptors
that are stimulated by the neurotransmitter
 An action potential is started in the dendrite
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Transmission of a Signal at Synapses
Axon of
transmitting
neuron
Axon
terminal
Action
potential
arrives
Vesicles
Synaptic
cleft
Receiving
neuron
Synapse
Transmitting neuron
Vesicle
fuses with
plasma
membrane
Neurotransmitter is released into
synaptic cleft
Neurotransmitter
molecules
Synaptic cleft
Ion channels
Neurotransmitter binds
to receptor
on receiving
neuron’s
membrane
Receiving neuron
Neurotransmitter
Receptor
Neurotransmitter
broken down
and released
Na+
Na+
Ion channel opens
Ion channel closes
Figure 7.10
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Transmission of a Signal at Synapses
Axon of
transmitting
neuron
Axon
terminal
Action
potential
arrives
Vesicles
Synaptic
cleft
Receiving
neuron
Synapse
Figure 7.10, step 1
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Transmission of a Signal at Synapses
Axon of
transmitting
neuron
Axon
terminal
Action
potential
arrives
Vesicles
Synaptic
cleft
Receiving
neuron
Synapse
Transmitting neuron
Vesicle
fuses with
plasma
membrane
Synaptic cleft
Ion channels
Receiving neuron
Figure 7.10, step 2
Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings
Transmission of a Signal at Synapses
Axon of
transmitting
neuron
Axon
terminal
Action
potential
arrives
Vesicles
Synaptic
cleft
Receiving
neuron
Synapse
Transmitting neuron
Vesicle
fuses with
plasma
membrane
Synaptic cleft
Ion channels
Neurotransmitter is released into
synaptic cleft
Neurotransmitter
molecules
Receiving neuron
Figure 7.10, step 3
Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings
Transmission of a Signal at Synapses
Axon of
transmitting
neuron
Axon
terminal
Action
potential
arrives
Vesicles
Synaptic
cleft
Receiving
neuron
Transmitting neuron
Vesicle
fuses with
plasma
membrane
Synaptic cleft
Ion channels
Neurotransmitter is released into
synaptic cleft
Synapse
Neurotransmitter binds
to receptor
on receiving
neuron’s
membrane
Neurotransmitter
molecules
Receiving neuron
Figure 7.10, step 4
Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings
Transmission of a Signal at Synapses
Axon of
transmitting
neuron
Axon
terminal
Action
potential
arrives
Vesicles
Synaptic
cleft
Receiving
neuron
Transmitting neuron
Vesicle
fuses with
plasma
membrane
Neurotransmitter is released into
synaptic cleft
Neurotransmitter binds
to receptor
on receiving
neuron’s
membrane
Neurotransmitter
molecules
Synaptic cleft
Ion channels
Synapse
Receiving neuron
Neurotransmitter
Receptor
Na+
Ion channel opens
Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings
Figure 7.10, step 5
Transmission of a Signal at Synapses
Axon
Axon of
terminal
transmitting
neuron
Vesicles
Action
potential
arrives
Synaptic
cleft
Receiving
neuron
Transmitting neuron
Vesicle
fuses with
plasma
membrane
Neurotransmitter is released into
synaptic cleft
Neurotransmitter binds
to receptor
on receiving
neuron’s
membrane
Neurotransmitter
molecules
Synaptic cleft
Ion channels
Synapse
Receiving neuron
Neurotransmitter
Receptor
Na+
Ion channel opens
Neurotransmitter
broken down
and released
Na+
Ion channel closes
Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings
Figure 7.10, step 6
Transmission of a Signal at Synapses
Axon
terminal
Axon of
transmitting
neuron
Action
potential
arrives
Vesicles
Synaptic
cleft
Receiving
neuron
Synapse
Transmitting neuron
Vesicle
fuses with
plasma
membrane
Neurotransmitter is released into
synaptic cleft
Neurotransmitter
molecules
Synaptic cleft
Ion channels
Neurotransmitter binds
to receptor
on receiving
neuron’s
membrane
Receiving neuron
Neurotransmitter
Receptor
Na+
Ion channel opens
Neurotransmitter
broken down
and released
Na+
Ion channel closes
Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings
Figure 7.10, step 7
The Reflex Arc
 Reflex—rapid, predictable, and involuntary
response to a stimulus
 Occurs over pathways called reflex arcs
 Reflex arc—direct route from a sensory neuron, to
an interneuron, to an effector
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The Reflex Arc
Skin
Spinal cord
(in cross section)
Stimulus at distal
end of neuron
Sensory neuron
Receptor
Motor neuron
(a)
Effector
Integration
center
Interneuron
Figure 7.11a
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The Reflex Arc
Skin
Stimulus at distal
end of neuron
Receptor
(a)
Figure 7.11a, step 1
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The Reflex Arc
Skin
Stimulus at distal
end of neuron
Sensory neuron
Receptor
(a)
Figure 7.11a, step 2
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The Reflex Arc
Skin
Stimulus at distal
end of neuron
Spinal cord
(in cross section)
Sensory neuron
Receptor
Integration
center
Interneuron
(a)
Figure 7.11a, step 3
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The Reflex Arc
Skin
Stimulus at distal
end of neuron
Spinal cord
(in cross section)
Sensory neuron
Receptor
Motor neuron
Integration
center
Interneuron
(a)
Figure 7.11a, step 4
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The Reflex Arc
Skin
Spinal cord
(in cross section)
Stimulus at distal
end of neuron
Sensory neuron
Receptor
Motor neuron
(a)
Effector
Integration
center
Interneuron
Figure 7.11a, step 5
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Simple Reflex Arc
Sensory receptors
(stretch receptors
in the quadriceps
muscle)
Sensory (afferent)
neuron
Spinal cord
Sensory receptors
(pain receptors in
the skin)
Sensory (afferent)
neuron
Synapse in
ventral horn
gray matter
Interneuron
Motor
(efferent)
neuron
Motor
(efferent)
neuron
(b)
Effector
(quadriceps
muscle of
thigh)
Effector
(biceps
brachii
muscle)
(c)
Figure 7.11b–c
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Simple Reflex Arc
Sensory receptors
(stretch receptors
in the quadriceps
muscle)
Spinal cord
(b)
Figure 7.11b, step 1
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Simple Reflex Arc
Sensory receptors
(stretch receptors
in the quadriceps
muscle)
Sensory (afferent)
neuron
Spinal cord
(b)
Figure 7.11b, step 2
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Simple Reflex Arc
Sensory receptors
(stretch receptors
in the quadriceps
muscle)
Sensory (afferent)
neuron
Spinal cord
Synapse in
ventral horn
gray matter
(b)
Figure 7.11b, step 3
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Simple Reflex Arc
Sensory receptors
(stretch receptors
in the quadriceps
muscle)
Sensory (afferent)
neuron
Spinal cord
Synapse in
ventral horn
gray matter
Motor
(efferent)
neuron
(b)
Figure 7.11b, step 4
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Simple Reflex Arc
Sensory receptors
(stretch receptors
in the quadriceps
muscle)
Sensory (afferent)
neuron
Spinal cord
Synapse in
ventral horn
gray matter
(b)
Motor
(efferent)
neuron
Effector
(quadriceps
muscle of
thigh)
Figure 7.11b, step 5
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Simple Reflex Arc
Sensory receptors
(pain receptors in
the skin)
Spinal cord
(c)
Figure 7.11c, step 1
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Simple Reflex Arc
Sensory receptors
(pain receptors in
the skin)
Spinal cord
Sensory (afferent)
neuron
(c)
Figure 7.11c, step 2
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Simple Reflex Arc
Sensory receptors
(pain receptors in
the skin)
Spinal cord
Sensory (afferent)
neuron
Interneuron
(c)
Figure 7.11c, step 3
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Simple Reflex Arc
Sensory receptors
(pain receptors in
the skin)
Spinal cord
Sensory (afferent)
neuron
Interneuron
Motor
(efferent)
neuron
(c)
Figure 7.11c, step 4a
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Simple Reflex Arc
Sensory receptors
(pain receptors in
the skin)
Spinal cord
Sensory (afferent)
neuron
Interneuron
Motor
(efferent)
neuron
Effector
(biceps
brachii
muscle)
(c)
Figure 7.11c, step 4b
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Simple Reflex Arc
Sensory receptors
(stretch receptors
in the quadriceps
muscle)
Sensory (afferent)
neuron
Spinal cord
Sensory receptors
(pain receptors in
the skin)
Sensory (afferent)
neuron
Synapse in
ventral horn
gray matter
Interneuron
Motor
(efferent)
neuron
Motor
(efferent)
neuron
(b)
Effector
(quadriceps
muscle of
thigh)
Effector
(biceps
brachii
muscle)
(c)
Figure 7.11b–c
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Types of Reflexes and Regulation
 Somatic reflexes
 Activation of skeletal muscles
 Example: When you move your hand away
from a hot stove
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Types of Reflexes and Regulation
 Autonomic reflexes
 Smooth muscle regulation
 Heart and blood pressure regulation
 Regulation of glands
 Digestive system regulation
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Types of Reflexes and Regulation
 Patellar, or knee-jerk, reflex is an example of a
two-neuron reflex arc
Figure 7.11d
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Central Nervous System (CNS)
 CNS develops from the embryonic neural tube
 The neural tube becomes the brain and spinal
cord
 The opening of the neural tube becomes the
ventricles
 Four chambers within the brain
 Filled with cerebrospinal fluid
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Central Nervous System (CNS)
Figure 7.12a
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Regions of the Brain
 Cerebral hemispheres (cerebrum)
 Diencephalon
 Brain stem
 Cerebellum
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Regions of the Brain: Cerebrum
Figure 7.12b
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Regions of the Brain: Cerebrum
 Cerebral Hemispheres (Cerebrum)
 Paired (left and right) superior parts of the
brain
 Includes more than half of the brain mass
 The surface is made of ridges (gyri) and
grooves (sulci)
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Regions of the Brain: Cerebrum
Figure 7.13a
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Regions of the Brain: Cerebrum
 Lobes of the cerebrum
 Fissures (deep grooves) divide the cerebrum
into lobes
 Surface lobes of the cerebrum
 Frontal lobe
 Parietal lobe
 Occipital lobe
 Temporal lobe
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Regions of the Brain: Cerebrum
Figure 7.13b
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Regions of the Brain: Cerebrum
 Specialized areas of the cerebrum
 Primary somatic sensory area
 Receives impulses from the body’s
sensory receptors
 Located in parietal lobe
 Primary motor area
 Sends impulses to skeletal muscles
 Located in frontal lobe
 Broca’s area
 Involved in our ability to speak
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Regions of the Brain: Cerebrum
Figure 7.13c
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Regions of the Brain: Cerebrum
Figure 7.14
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Regions of the Brain: Cerebrum
 Cerebral areas involved in special senses
 Gustatory area (taste)
 Visual area
 Auditory area
 Olfactory area
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Regions of the Brain: Cerebrum
 Interpretation areas of the cerebrum
 Speech/language region
 Language comprehension region
 General interpretation area
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Regions of the Brain: Cerebrum
Figure 7.13c
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Regions of the Brain: Cerebrum
 Layers of the cerebrum
 Gray matter—outer layer in the cerebral cortex
composed mostly of neuron cell bodies
 White matter—fiber tracts deep to the gray
matter
 Corpus callosum connects hemispheres
 Basal nuclei—islands of gray matter buried within
the white matter
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Regions of the Brain: Cerebrum
Figure 7.15
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Regions of the Brain: Diencephalon
Figure 7.16
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Regions of the Brain: Diencephalon
 Sits on top of the brain stem
 Enclosed by the cerebral hemispheres
 Made of three parts
 Thalamus
 Hypothalamus
 Epithalamus
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Regions of the Brain: Diencephalon
Figure 7.12b
Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings
Regions of the Brain: Diencephalon
Figure 7.16a
Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings
Regions of the Brain: Diencephalon
Figure 7.16b
Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings
Regions of the Brain: Diencephalon
 Thalamus
 Surrounds the third ventricle
 The relay station for sensory impulses
 Transfers impulses to the correct part of the
cortex for localization and interpretation
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Regions of the Brain: Diencephalon
 Hypothalamus
 Under the thalamus
 Important autonomic nervous system center
 Helps regulate body temperature
 Controls water balance
 Regulates metabolism
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Regions of the Brain: Diencephalon
 Hypothalamus (continued)
 An important part of the limbic system
(emotions)
 The pituitary gland is attached to the
hypothalamus
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Regions of the Brain: Diencephalon
 Epithalamus
 Forms the roof of the third ventricle
 Houses the pineal body (an endocrine gland)
 Includes the choroid plexus—forms
cerebrospinal fluid
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Regions of the Brain: Brain Stem
 Attaches to the spinal cord
 Parts of the brain stem
 Midbrain
 Pons
 Medulla oblongata
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Regions of the Brain: Brain Stem
Figure 7.16a
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Regions of the Brain: Brain Stem
 Midbrain
 Mostly composed of tracts of nerve fibers
 Has two bulging fiber tracts—
cerebral peduncles
 Has four rounded protrusions—
corpora quadrigemina
 Reflex centers for vision and hearing
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Regions of the Brain: Brain Stem
 Pons
 The bulging center part of the brain stem
 Mostly composed of fiber tracts
 Includes nuclei involved in the control of
breathing
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Regions of the Brain: Brain Stem
 Medulla Oblongata
 The lowest part of the brain stem
 Merges into the spinal cord
 Includes important fiber tracts
 Contains important control centers
 Heart rate control
 Blood pressure regulation
 Breathing
 Swallowing
 Vomiting
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Regions of the Brain: Brain Stem
 Reticular Formation
 Diffuse mass of gray matter along the brain
stem
 Involved in motor control of visceral organs
 Reticular activating system (RAS) plays a role
in awake/sleep cycles and consciousness
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Regions of the Brain:
Reticular Formation of the Brain Stem
Figure 7.16b
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Regions of the Brain: Cerebellum
 Two hemispheres with convoluted surfaces
 Provides involuntary coordination of body
movements
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Regions of the Brain: Cerebellum
Figure 7.16a
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Protection of the Central Nervous System
 Scalp and skin
 Skull and vertebral column
 Meninges
 Cerebrospinal fluid (CSF)
 Blood-brain barrier
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Protection of the Central Nervous System
Figure 7.17a
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Meninges
 Dura mater
 Double-layered external covering
 Periosteum—attached to inner surface of
the skull
 Meningeal layer—outer covering of the
brain
 Folds inward in several areas
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Meninges
 Arachnoid layer
 Middle layer
 Web-like
 Pia mater
 Internal layer
 Clings to the surface of the brain
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Meninges
Figure 7.17b
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Cerebrospinal Fluid (CSF)
 Similar to blood plasma composition
 Formed by the choroid plexus
 Forms a watery cushion to protect the brain
 Circulated in arachnoid space, ventricles, and
central canal of the spinal cord
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Ventricles and Location of
the Cerebrospinal Fluid
Figure 7.18a–b
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Ventricles and Location of
the Cerebrospinal Fluid
Figure 7.18c
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Hydrocephalus in a Newborn
 Hydrocephalus
 CSF accumulates and exerts pressure on the
brain if not allowed to drain
Figure 7.19
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Blood-Brain Barrier
 Includes the least permeable capillaries of the
body
 Excludes many potentially harmful substances
 Useless as a barrier against some substances
 Fats and fat soluble molecules
 Respiratory gases
 Alcohol
 Nicotine
 Anesthesia
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Traumatic Brain Injuries
 Concussion
 Slight brain injury
 No permanent brain damage
 Contusion
 Nervous tissue destruction occurs
 Nervous tissue does not regenerate
 Cerebral edema
 Swelling from the inflammatory response
 May compress and kill brain tissue
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Cerebrovascular Accident (CVA)
 Commonly called a stroke
 The result of a ruptured blood vessel supplying a
region of the brain
 Brain tissue supplied with oxygen from that blood
source dies
 Loss of some functions or death may result
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Alzheimer’s Disease
 Progressive degenerative brain disease
 Mostly seen in the elderly, but may begin in
middle age
 Structural changes in the brain include abnormal
protein deposits and twisted fibers within neurons
 Victims experience memory loss, irritability,
confusion, and ultimately, hallucinations and
death
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Spinal Cord
 Extends from the foramen magnum of the skull to
the first or second lumbar vertebra
 31 pairs of spinal nerves arise from the spinal
cord
 Cauda equina is a collection of spinal nerves at
the inferior end
 L1 – L2
 Lumbar punctures and epidurals
 L3
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Spinal Cord Anatomy
Figure 7.20 (1 of 2)
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Spinal Cord Anatomy
Figure 7.20 (2 of 2)
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Spinal Cord Anatomy
 Internal gray matter is mostly cell bodies
 Dorsal (posterior) horns
 Anterior (ventral) horns
 Gray matter surrounds the central canal
 Central canal is filled with cerebrospinal
fluid
 Exterior white mater—conduction tracts
 Dorsal, lateral, ventral columns
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Spinal Cord Anatomy
Figure 7.21
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Spinal Cord Anatomy
 Meninges cover the spinal cord
 Spinal nerves leave at the level of each vertebrae
 Dorsal root
 Associated with the dorsal root ganglia—
collections of cell bodies outside the
central nervous system
 Ventral root
 Contains axons
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Pathways Between Brain and Spinal Cord
Figure 7.22
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Peripheral Nervous System (PNS)
 Nerves and ganglia outside the central nervous
system
 Nerve = bundle of neuron fibers
 Neuron fibers are bundled by connective tissue
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PNS: Structure of a Nerve
 Endoneurium surrounds each fiber
 Groups of fibers are bound into fascicles by
perineurium
 Fascicles are bound together by epineurium
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PNS: Structure of a Nerve
Figure 7.23
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PNS: Classification of Nerves
 Mixed nerves
 Both sensory and motor fibers
 Sensory (afferent) nerves
 Carry impulses toward the CNS
 Motor (efferent) nerves
 Carry impulses away from the CNS
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PNS: Cranial Nerves
 12 pairs of nerves that mostly serve the head and
neck
 Only the pair of vagus nerves extend to thoracic
and abdominal cavities
 Most are mixed nerves, but three are sensory only
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PNS: Cranial Nerves
 I Olfactory nerve—sensory for smell
 II Optic nerve—sensory for vision
 III Oculomotor nerve—motor fibers to eye
muscles
 IV Trochlear—motor fiber to eye muscles
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PNS: Cranial Nerves
 V Trigeminal nerve—sensory for the face; motor
fibers to chewing muscles
 VI Abducens nerve—motor fibers to eye muscles
 VII Facial nerve—sensory for taste; motor fibers
to the face
 VIII Vestibulocochlear nerve—sensory for
balance and hearing
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PNS: Cranial Nerves
 IX Glossopharyngeal nerve—sensory for taste;
motor fibers to the pharynx
 X Vagus nerves—sensory and motor fibers for
pharynx, larynx, and viscera
 XI Accessory nerve—motor fibers to neck and
upper back
 XII Hypoglossal nerve—motor fibers to tongue
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PNS: The Cranial Nerves
Table 7.1 (1 of 4)
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PNS: The Cranial Nerves
Table 7.1 (2 of 4)
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PNS: The Cranial Nerves
Table 7.1 (3 of 4)
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PNS: The Cranial Nerves
Table 7.1 (4 of 4)
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PNS: Distribution of Cranial Nerves
Figure 7.24
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PNS: Spinal Nerves
 There is a pair of spinal nerves at the level of each
vertebrae for a total of 31 pairs
 Formed by the combination of the ventral and
dorsal roots of the spinal cord
 Named for the region from which they arise
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PNS: Spinal Nerves
Figure 7.25a
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PNS: Anatomy of Spinal Nerves
 Spinal nerves divide soon after leaving the spinal
cord
 Dorsal rami—serve the skin and muscles of
the posterior trunk
 Ventral rami—form a complex of networks
(plexus) for the anterior
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PNS: The Spinal Nerves
Figure 7.25b
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PNS: Spinal Nerve Plexuses
Table 7.2 (1 of 2)
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PNS: Spinal Nerve Plexuses
Table 7.2 (2 of 2)
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PNS: Distribution of Major Peripheral
Nerves of the Upper and Lower Limbs
Figure 7.26a
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PNS: Distribution of Major Peripheral
Nerves of the Upper and Lower Limbs
Figure 7.26b
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PNS: Distribution of Major Peripheral
Nerves of the Upper and Lower Limbs
Figure 7.26c
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PNS: Autonomic Nervous System
 Motor subdivision of the PNS
 Consists only of motor nerves
 Also known as the involuntary nervous system
 Regulates activities of cardiac and smooth
muscles and glands
 Two subdivisions
 Sympathetic division
 Parasympathetic division
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PNS: Differences Between Somatic
and Autonomic Nervous Systems
 Nerves
 Somatic: one motor neuron
 Autonomic: preganglionic and postganglionic
nerves
 Effector organs
 Somatic: skeletal muscle
 Autonomic: smooth muscle, cardiac muscle,
and glands
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PNS: Differences Between Somatic
and Autonomic Nervous Systems
 Neurotransmitters
 Somatic: always use acetylcholine
 Autonomic: use acetylcholine, epinephrine, or
norepinephrine
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PNS: Comparison of Somatic
and Autonomic Nervous Systems
Figure 7.27
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PNS: Anatomy of the Sympathetic Division
 Originates from T1 through L2
 Ganglia are at the sympathetic trunk (near the
spinal cord)
 Short pre-ganglionic neuron and long postganglionic neuron transmit impulse from CNS to
the effector
 Norepinephrine and epinephrine are
neurotransmitters to the effector organs
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PNS: Anatomy of the
Autonomic Nervous System
Figure 7.28
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PNS: Sympathetic Pathways
Figure 7.29
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PNS: Anatomy of the Parasympathetic Division
 Originates from the brain stem and S1 through S4
 Terminal ganglia are at the effector organs
 Always uses acetylcholine as a neurotransmitter
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PNS: Autonomic Functioning
 Sympathetic—“fight or flight”
 Response to unusual stimulus
 Takes over to increase activities
 Remember as the “E” division
 Exercise, excitement, emergency, and
embarrassment
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PNS: Autonomic Functioning
 Parasympathetic—“housekeeping” activites
 Conserves energy
 Maintains daily necessary body functions
 Remember as the “D” division
 digestion, defecation, and diuresis
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Effects of the Sympathetic and
Parasympathetic Divisions of the ANS
Table 7.3 (1 of 2)
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Effects of the Sympathetic and
Parasympathetic Divisions of the ANS
Table 7.3 (2 of 2)
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Development Aspects of the Nervous System
 The nervous system is formed during the first
month of embryonic development
 Any maternal infection can have extremely
harmful effects
 The hypothalamus is one of the last areas of the
brain to develop
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Development Aspects of the Nervous System
 No more neurons are formed after birth, but
growth and maturation continues for several
years (mostly)
 The brain reaches maximum weight as a young
adult
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