Chapter 11 Fundamentals of the Nervous System and Nervous Tissue Part A.

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 columnar-shaped cells

47b

Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings

Figure 7.17b

CEREBROSPINAL FLUID- SHOWN CIRCULATING BY ARROWS

Protection of the Central Nervous SystemProtection of the Central Nervous System

Slide 7.44a


Figure 7.16a

47b


Figure 7.17b

CEREBROSPINAL FLUID

Figure 11.3d, e

Oligodendrocytes, Schwann Cells,

and Satellite CellsIN CNS

IN PNS

• Oligodendrocytes –

• Schwann cells (neurolemmocytes) –

• Satellite cells-

Neuron Neuron

AnatomyAnatomy

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 -

• Nucleolus-

• Where outgrowth of neuronal processes

• There are no centrioles (amitotic nature)

• Nissl bodies-

• Axon 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 ClassificationNeuron Classification

Slide 7.15Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings

Figure 7.6

StructuralStructural Classification of Neurons Classification of Neurons

Slide 7.16a


Multipolar neurons –

Figure 7.8a

Structural Classification of NeuronsStructural Classification of Neurons

Slide 7.16b


Bipolar neurons –

Figure 7.8b

Structural Classification of NeuronsStructural Classification of Neurons

Slide 7.16c


Unipolar neurons –

Figure 7.8c

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

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Chapter 11 Fundamentals of the Nervous System and Nervous Tissue Part A.

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