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Chapter 11
Fundamentals of the Nervous
System and Nervous Tissue
Part A
Nervous System
• The master controlling and communicating
system of the body
• Functions:
1-Sensory input –
Figure 11.1
Nervous System
2-Integration –
3- Motor output –
Figure 11.1
Organization of the Nervous
System
• Central nervous system (CNS)
• Peripheral nervous system (PNS)
Two principal cell types
• Neurons –
• Supporting cells –
Supporting Cells: Neuroglia
(glia)
• Provide a supportive scaffolding for neurons
• Segregate and insulate neurons
Astrocytes
Figure 11.3a
Astrocytes
• Most abundant, versatile, and highly
branched glial cells
• They cling to neurons and cover capillaries
Microglia and Ependymal Cells
Figure 11.3b, c
Microglia and Ependymal Cells
• Microglia –
• Ependymal cells – squamous- to columnarshaped cells
CEREBROSPINAL FLUID- SHOWN CIRCULATING BY
ARROWS
Figure 7.17b
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Slide
Protection of the Central Nervous System
Figure 7.16a
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Slide
CEREBROSPINAL FLUID
Figure 7.17b
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Slide
Oligodendrocytes, Schwann Cells,
and Satellite Cells
IN CNS
IN PNS
Figure 11.3d, e
• Oligodendrocytes –
• Schwann cells (neurolemmocytes) –
• Satellite cells-
Neuron
Anatomy
Neurons (Nerve Cells)
– Composed of a body, axon, and dendrites
– Long-lived (over 100 yrs), amitotic, and have a
high metabolic rate
• functions in:
– Electrical signaling
– Cell-to-cell signaling during development
Nerve Cell Body (Soma)
•
•
•
•
•
•
nucleus NucleolusWhere outgrowth of neuronal processes
There are no centrioles (amitotic nature)
Nissl bodiesAxon hillock –
Processes
•
•
•
•
Armlike extensions from the soma
Called
in the CNS
Called
in the PNS
Two types:
Dendrites of Motor Neurons
• Short, tapering, and branched
• They are the receptive, or input, regions of
the neuron
Axons: Structure
• Slender processes of uniform diameter
arising from the hillock
• Long axons are called nerve fibers
• Usually there is only one unbranched axon
per neuron
• Axonal terminal – branched terminus of an
axon
Axons: Function
• Generate and transmit action potentials
• Secrete neurotransmitters from the axonal
terminals
Neuron Classification
Figure 7.6
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Slide 7.15
Structural Classification of Neurons
 Multipolar neurons –
Figure 7.8a
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Slide
Structural Classification of Neurons
 Bipolar neurons –
Figure 7.8b
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
Slide
Structural Classification of Neurons
 Unipolar neurons –
Figure 7.8c
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
Slide
Nodes of Ranvier (Neurofibral
Nodes)
• Gaps in the myelin sheath between
adjacent Schwann cells
• They are the sites where collaterals can
emerge (see 1st neuron pic)
Myelin Sheath and Neurilemma:
Formation
Figure 11.5a-d
• In MS, myelin is lost in multiple areas, leaving scar
tissue called sclerosis.
• These damaged areas are also known as plaques
or lesions.
Myelin sheath is green
Axon is yellow
Myelin Sheath
• Whitish, fatty (lipoprotein), segmented
sheath around most long axons
• It functions in:
• Formed by Schwann cells in the PNS
• A Schwann cell:
– Envelopes an axon in a trough
– Encloses the axon with its plasma membrane
– Concentric layers of membrane make up the
myelin sheath
• Neurilemma – remaining nucleus and
cytoplasm of a Schwann cell
Unmyelinated Axons
• A Schwann cell surrounds nerve fibers but
coiling does not take place
• SEE HW PG. 256 #12 A
Axons of the CNS
• Both myelinated and unmyelinated fibers
are present
• Myelin sheaths are formed by
• Nodes of Ranvier are widely spaced
Regions of the Brain and Spinal
• White matter –
• Gray matter –
• Basal nuclei –
Gray matter
White matter