Download 7.1 Functions of the Nervous System

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
 They activate muscles and glands
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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
 Can be divided into sympathetic and
parasympathetic
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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
 Cells are called glial cells
 Have special functions
 Can’t transport impulses
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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
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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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Multiple Sclerosis
 Myelin sheath around nerve fiber is gradually
destroyed
 Converted to hardened sheaths called scelroses
 Is an autoimmune disorder
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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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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
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
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
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
Figure 7.10, step 1
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
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
Impairment of Electrical Impulses
 Sedatives and anesthetics block nerve impulses
by altering membrane permeability to sodium ions
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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
Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings
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
Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings
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
Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings
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
Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings
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
Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings
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
Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings
Simple Reflex Arc
Sensory receptors
(pain receptors in
the skin)
Spinal cord
Sensory (afferent)
neuron
Interneuron
(c)
Figure 7.11c, step 3
Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings
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
Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings
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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