Human Biology
Sylvia S. Mader
Michael Windelspecht
Chapter 13
Nervous
System
Lecture Outline
Part 1
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Nervous System
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Points to ponder
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What are the 3 types of neurons?
What are neuroglia?
What is the structure of a neuron?
What is the myelin sheath? Saltatory conduction?
Schwann cell? Node of Ranvier?
Explain the resting and action potential as they relate to a
nerve impulse.
How does the nerve impulse traverse the synapse?
What are the 2 parts of the nervous system?
What 3 things protect the CNS?
What are the 4 parts of the brain and their functions?
What is the reticular activating system and the limbic
system?
What are some higher mental functions of the brain?
What are the 2 parts of the peripheral nervous system?
How do abused drugs work?
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13.1 Overview of the Nervous System
The nervous divisions
• 2 divisions
– __________________ (CNS): Brain and
spinal cord
– __________________ (PNS): Nerves
and ganglia (collections of cell bodies)
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13.1 Overview of the Nervous System
The nervous divisions
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
brain
Central Nervous System (CNS)
cranial nerves
brain
spinal cord
spinal cord
spinal nerves
Peripheral Nervous System (PNS)
sensory (afferent) nerves —
carry sensory information
into brain and spinal cord
somatic sensory
nerves: signals
from skin,
muscles,
joints, special
senses
a.
Figure 13.1 The two divisions of the nervous system.
visceral sensory
nerves:
signals from
body organs
motor (efferent) nerves —
carry motor information
from CNS to effectors
somatic motor
nerves: signals
to skeletal
muscles,
voluntary
autonomic motor
nerves: signals
to smooth
muscle, cardiac
muscle, glands,
involuntary
sympathetic
division
“fight or flight”
parasympathetic
division
“rest and digest”
b.
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13.1 Overview of the Nervous System
The nervous system
• The nervous system allows for
_____________ between cells through
sensory input, integration of data, and
motor output.
• 2 cell types: _______ and ________
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13.1 Overview of the Nervous System
Expanding on neurons
• 3 types of neurons
• _________ – takes impulses from sensory
receptor to CNS
• _________ – receives information in the
CNS and sends it to a motor neuron
• ______ – takes impulses from the CNS to an
effector (i.e., gland or muscle fiber)
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13.1 Overview of the Nervous System
Expanding on neurons
• Neuron structure (Ch. 4 review)
• Cell body – main cell where nucleus and
most organelles reside
• Dendrites – many short extensions that
carry impulses to a cell body
• Axon (nerve fiber) – single, long extension
that carries impulses away from the cell
body
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13.1 Overview of the Nervous System
Types of neurons
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
a. Sensory
neuron
sensory
receptor
cell body
axon
myelin
sheath
direction
of conduction
Schwann
cell
b. Interneuron
400 nm
axon
dendrite
c. Motor neuron
cell body
axon
node of Ranvier
2.7 μm
axon terminal
Figure 13.2 The structure
of sensory neurons,
interneurons, and motor
neurons.
direction
of conduction
a (myelin): © M.B. Bunge/Biological Photo Service; c (cell body): © Manfred Kage/Peter Arnold/Photolibrary
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13.1 Overview of the Nervous System
The myelin sheath
• A lipid covering on long axons that acts to
increase the speed of nerve impulse conduction,
insulation, and regeneration in the PNS
• _____________ – neuroglia that make up the
myelin sheath in the PNS
• _____________ – gaps between myelination on
the axons
• Saltatory conduction – conduction of the nerve
impulse from node to node
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13.1 Overview of the Nervous System
Neuron structure
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
a. Sensory
neuron
sensory
receptor
cell body
axon
myelin
sheath
direction
of conduction
Schwann
cell
b. Interneuron
400 nm
axon
dendrite
c. Motor neuron
cell body
axon
node of Ranvier
2.7 μm
axon terminal
Figure 13.2 The structure
of sensory neurons,
interneurons, and motor
neurons.
direction
of conduction
a (myelin): © M.B. Bunge/Biological Photo Service; c cell body): © Manfred Kage/Peter Arnold/Photolibrary
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13.1 Overview of the Nervous System
The nerve impulse: Resting potential (RP)
• ___________________ – when the axon is not
conducting a nerve impulse
• More positive ions outside than inside the
membrane
• Negative charge of -70 mV inside the axon
• More Na+ outside than inside
• More K+ inside than outside
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13.1 Overview of the Nervous System
The nerve impulse: Resting potential (RP)
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
reference
electrode
outside axon
recording
electrode
inside axon
axonal
membrane
+

+

+

+

+

+

+

+

+

+


+

+

+

+

+

+

+

+

+

+
inside axon
K+
Na+
gated K+
channel
outside axon
gated Na+
channel
a. Resting potential: Na+ outside the axon, K+ and large
anions inside the axon. Separation of charges polarizes
the cell and causes the resting potential.
Figure 13.3a Generation of an action potential.
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13.1 Overview of the Nervous System
The nerve impulse: Action potential
• ________________ – rapid change in the axon
membrane that allows a nerve impulse to occur
• Sodium gates open, letting Na+ in.
• Depolarization occurs.
• Interior of axon loses negative charge (-55 mV,
then +35 mV).
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13.1 Overview of the Nervous System
The nerve impulse: Action potential
• Potassium gates open, letting K+ out.
• _______________ occurs.
• Interior of axon regains ______________ charge
(-70 mV).
• Wave of depolarization/repolarization travels
down the axon.
• Resting potential is restored by moving
potassium inside and sodium outside.
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