Nervous System Notes A

PowerPoint®
Lecture Slide Presentation
by Patty Bostwick-Taylor,
Florence-Darlington Technical College
Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings
PART A
7
The Nervous
System

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

Functions of the Nervous System
 Motor output
 A response to integrated stimuli
 The response activates muscles or glands

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

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

Organization of the Nervous System
Figure 7.2

Functional Classification of
the Peripheral Nervous System
 Motor (efferent) division (continued)
 Two subdivisions
 Somatic nervous system = voluntary
 Autonomic nervous system = involuntary
Nervous Tissue: Support Cells
 Support cells in the CNS are grouped together as
“neuroglia”
 Function: to support, insulate, and protect
neurons

 Astrocytes
 Abundant, star-shaped cells
 Brace neurons
 Form barrier between capillaries and neurons
 Control the chemical environment of
the brain

 Microglia
 Spiderlike phagocytes
 Dispose of debris

 Ependymal cells
 Line cavities of the brain and spinal cord
 Circulate cerebrospinal fluid

 Oligodendrocytes
 Wrap around nerve fibers in the central
nervous system
 Produce myelin sheaths

 Satellite cells
 Protect neuron cell bodies
 Schwann cells
 Form myelin sheath in the peripheral nervous
system
*Oligodendrocytes wrap
central nerves and
Schwann cells wrap
peripheral nerves.

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

 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

Figure 7.4

 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
 http://www.youtube.com/watch?v=LT3VKAr4roo Synapse
Synaptic
Cleft

Figure 7.5

 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
 https://www.youtube.com/watch?v=G3WUJ9XaZWc saltatory
conduction
 http://www.youtube.com/watch?v=qgySDmRRzxY
 https://www.youtube.com/watch?v=i30Bv_E0qAU

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
 Ganglia—collections of cell bodies outside the central nervous
system

Functional Classification of Neurons
Figure 7.7

Functional Classification of Neurons
 Interneurons (association neurons)
 Found in neural pathways in the central
nervous system
 Connect sensory and motor neurons

Neuron Classification
Figure 7.6

Figure 7.8a
Structural Classification of Neurons
 Multipolar neurons—many extensions from the cell body

Functional Properties of Neurons
 Irritability
 Ability to respond to stimuli
 Conductivity
 Ability to transmit an impulse

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

Nerve Impulses
Figure 7.9a–b
http://www.youtube.com/watch?v=YP_P6bYvEjE

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
 http://www.youtube.com/watch?v=R0TdXkxBOkE

Nerve Impulses
Figure 7.9c–d

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

Nerve Impulses
Figure 7.9e–f

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

Figure 7.10, step 1
Axon
terminal
Vesicles
Synaptic
cleft
Action
potential
arrives
Synapse
Axon of
transmitting
neuron
Receiving
neuron

Figure 7.10, step 6
Neurotrans-
mitter is re-
leased into
synaptic cleft
Neurotrans-
mitter binds
to receptor
on receiving
neuron’s
membrane
Vesicle
fuses with
plasma
membrane
Synaptic cleft
Neurotransmitter
molecules
Ion channels
Receiving neuron
Transmitting neuron
Receptor
Neurotransmitter
Na+
Na+
Neurotransmitter
broken down
and released
Ion channel opens Ion channel closes

Nervous System Notes A

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