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Essentials of Human Anatomy & Physiology
Seventh Edition
Elaine N. Marieb
Chapter 7
The Nervous System
Slides 7.1 – 7.22
Lecture Slides in PowerPoint by Jerry L. Cook
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Overview of the Nervous System
Homeostatsis
Endocrine
System
Nervous
System
(uses chemicals, hormones, via
the blood stream to effect target
cells)
(uses electrochemical signals via
neurons to effect muscles and
glands)
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Slide 7.2
Overview of the Nervous System
Nervous
System
Central Nervous
System
Peripheral Nervous
System
(CNS)
(PNS)
Brain and spinal cord
Cranial and spinal nerves
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Slide 7.2
Overview of the Nervous System
Peripheral
Nervous
system
Sensory
(Afferent)
Division
(conveys impulses from sensory
receptors to the CNS)
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Motor (Efferent)
Division
(carries impulses from CNS to
effector organs, muscles, and
glands)
Slide 7.2
Overview of the Nervous System
Motor
(Efferent)
Division
Somatic
Nervous System
Autonomic
Nervous System
(voluntary control)
(involuntary control)
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Slide 7.2
Overview of the Nervous System
Autonomic
Nervous
System
Sympathetic
Division
Parasympathetic
Division
(“fight-or-flight” division)
(“resting and digesting” division)
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Slide 7.2
The Central Nervous System
 The CNS consists of the brain and
the spinal cord.
 They interpret incoming sensory input
and issue instructions for motor output.
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Slide 7.2
Functions of the Nervous System
 Sensory input – gathering information
 To monitor changes occurring inside and
outside the body
 Changes = stimuli
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Slide 7.1a
Functions of the Nervous System
 Integration
 To process and interpret sensory input and
decide if action is needed
 Motor output
 A response to integrated stimuli
 The response activates muscles or glands
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Slide 7.1b
Nervous Tissue: Support Cells
(Neuroglia)
Neuroglia
 support, insulate, and protect the
neurons of the CNS.
 resemble neurons but are not able to
transmit nerve impulses
 never lose their ability to divide,
whereas neurons do
Figure 7.3a
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Slide 7.5
Nervous Tissue: Support Cells
(Neuroglia)
Types of Neuroglia
 Astrocytes
 Microglial cell
 Ependymal cells
 Oligodendrocyte
Figure 7.3a
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Slide 7.5
Nervous Tissue: Support Cells
(Neuroglia)
 Astrocytes
 Connect neurons to blood capillaries, making
an anchor between the two
 Protect neurons from harmful substances that
might be in the blood
 Pick up excess ions and recapture released
neurotransmitters
Figure 7.3a
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Slide 7.5
Nervous Tissue: Support Cells
 Microglia
 Phagocytes that
dispose of debris
 Ependymal cells
 Ciliated cells that line
the cavities of the
brain and spinal cord
 Cilia circulates the
cerebrospinal
fluid, which cushions
the CNS
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Figure 7.3b, c
Slide 7.6
Nervous Tissue: Support Cells
 Oligodendrocytes
 Produce myelin
sheath coverings
around nerve
fibers, called
Schwann cells in
the PNS
Figure 7.3d
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Slide 7.7a
Nervous Tissue: Neurons
 Neurons = nerve cells
 Neurons are specialized cells that transmit
messages from one part of the body to
another
 Unlike neuroglia, neurons transmit nerve
impulses.
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Slide 7.8
Neuron Anatomy
 Cell body (clusters
called nuclei)
 Cell processes
 Axons
 Dendrites
 Axonal terminals
 Myelin sheath,
laid down by
oligodendrocytes,
which lack a
neurilemma
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Figure 7.4a
Slide 7.9a
The Synapse
 Neurons never touch each other. They
are separated by a tiny gap called the
synaptic cleft.
 The axonal terminal of the motor neuron
house vesicles that contain
neurotransmitters.
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Slide 7.11
Nerve Impulses
 Neurons serve two functions:
 Irritability (the ability to respond to a
stimulus and produce a nerve impulse)
 Conductivity (the ability to transmit the
impulse to other neurons, muscles, or
glands)
Figure 7.5
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Slide 7.12
Starting a Nerve Impulse
 Depolarization – a
stimulus depolarizes the
neuron’s membrane
 A deploarized
membrane allows
sodium (Na+) to flow
inside the membrane
 The exchange of ions
initiates an action
potential in the neuron
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Figure 7.9a–c
Slide 7.18
The Action Potential
 If the action potential (nerve impulse)
starts, it is propagated over the entire
axon
 Potassium ions rush out of the neuron
after sodium ions rush in, which
repolarizes the membrane
 The sodium-potassium pump restores
the original configuration
 This action requires ATP
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Slide 7.19
Nerve Impulse Propagation
 The impulse
continues to move
toward the cell body
 Impulses travel
faster when fibers
have a myelin
sheath
Figure 7.9c–e
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Slide 7.20
Continuation of the Nerve Impulse
between Neurons
 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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Slide 7.21
How Neurons Communicate at
Synapses
Figure 7.10
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Slide 7.22
Regions of the Brain
 Cerebral
hemispheres
 Diencephalon
 Brain stem
 Cerebellum
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Figure 7.12
Slide 7.27
Specialized Area of the Cerebrum
Figure 7.13c
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Slide 7.32c
Layers of the Cerebrum
 Gray matter
 Outer layer
 Composed
mostly of neuron
cell bodies
Figure 7.13a
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Slide 7.33a
Layers of the Cerebrum
 White matter
 Fiber tracts
inside the gray
matter
 Example:
corpus callosum
connects
hemispheres
Figure 7.13a
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Slide 7.33b
Layers of the Cerebrum
 Basal nuclei –
internal islands
of gray matter
Figure 7.13a
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Slide 7.33c
Protection of the Central Nervous
System
 Scalp and skin
 Skull and vertebral column
 Meninges
Figure 7.16a
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Slide 7.44a
Protection of the Central Nervous
System
 Cerebrospinal fluid
 Blood brain barrier
Figure 7.16a
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Slide 7.44b
Meninges
 Dura mater
 Double-layered external covering
 Periosteum – attached to surface of the
skull
 Meningeal layer – outer covering of the
brain
Folds inward in several areas
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Slide 7.45a
Meninges
 Arachnoid layer
 Middle layer
 Web-like
 Pia mater
 Internal layer
 Clings to the surface of the brain
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Slide 7.45b
Cerebrospinal Fluid
 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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Slide 7.46
Ventricles and Location of the
Cerebrospinal Fluid
Figure 7.17b
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Slide 7.47b
Blood Brain Barrier
 Includes the least permeable capillaries
of the body
 Excludes many potentially harmful
substances
 Useless against some substances
 Fats and fat soluble molecules
 Respiratory gases
 Alcohol
 Nicotine
 Anesthesia
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Slide 7.48
Spinal Cord
 Extends from the
medulla oblongata to
the region of T12
 Below T12 is the cauda
equina (a collection of
spinal nerves)
 Enlargements occur in
the cervical and lumbar
regions
Figure 7.18
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Slide 7.52
Spinal Cord Anatomy
 Exterior white mater – conduction tracts
Figure 7.19
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Slide 7.53a
Spinal Cord Anatomy
 Internal gray matter - mostly cell bodies
 Dorsal (posterior) horns
 Anterior (ventral) horns
Figure 7.19
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Slide 7.53b
Spinal Cord Anatomy
 Central canal filled with cerebrospinal
fluid
Figure 7.19
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Slide 7.53c
Spinal Cord Anatomy
 Meninges cover the spinal cord
 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
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Slide 7.54
Peripheral Nervous System
 Nerves and ganglia outside the central
nervous system
 Nerve = bundle of neuron fibers
 Neuron fibers are bundled by
connective tissue
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Slide 7.55
Classification of Nerves
 Mixed nerves – both sensory and motor
fibers
 Afferent (sensory) nerves – carry
impulses toward the CNS
 Efferent (motor) nerves – carry impulses
away from the CNS
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Slide 7.57
Cranial Nerves
 12 pairs of nerves that mostly serve the
head and neck
 Numbered in order, front to back
 Most are mixed nerves, but three are
sensory only
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Slide 7.58
Distribution of Cranial Nerves
Figure 7.21
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Slide 7.59
Spinal Nerves
 There is a pair of spinal nerves at the
level of each vertebrae for a total of 31
pairs
 Spinal nerves are formed by the
combination of the ventral and dorsal
roots of the spinal cord
 Spinal nerves are named for the region
from which they arise
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Slide 7.63
Spinal Nerves
Figure 7.22a
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Slide 7.64
Examples of Nerve Distribution
Figure 7.23
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Slide 7.66
Autonomic Nervous System
 The involuntary branch of the nervous
system
 Consists of only motor nerves
 Divided into two divisions
 Sympathetic division
 Parasympathetic division
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Slide 7.67
Anatomy of the Sympathetic
Division
 Originates from T1 through L2 vertebrae
 Norepinephrine and epinephrine are
neurotransmitters to the effector organs
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Slide 7.70
Anatomy of the Parasympathetic
Division
 Originates from the brain stem and S1
through S4 vertebrae
 Always uses acetylcholine as a
neurotransmitter
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Slide 7.72
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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Slide 7.74a
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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Slide 7.74b
Development Aspects of the
Nervous System
 No more neurons are formed after birth,
but growth and maturation continues for
several years
 The brain reaches maximum weight as
a young adult (about 3 pounds)
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Slide 7.75b