Download The Nervous System - INAYA Medical College

CHAPTER 11
Fundamentals of the
Nervous System and
Nervous Tissue
Part A
LEARNING OBJECTIVES
At the end of the discussion students should be
able to :
• Explain the Organization of Nervous system
• Define and enlist the histological structures of
Nervous Tissue.
• Recognize and compare the structural and
functional classification of Neurons
• Explain the developmental aspects of Neurons
LECTURE OUTLINE


Organization of the Nervous System
Histology of Nervous Tissue
1.
2.
3.
4.


Neuron
Neuroglia cells
Structural Classification of Neurons
Functional Classification of Neurons
Grey mater and white mater
Developmental Aspects of Neurons
Before starting lets have a look on the basic
function of nervous system.
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The Nervous System
The nervous system is the master controlling and
communicating system of the body. Nervous system
has three overlapping systems.
1. Sensory input
2. Integration
3. Motor output
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Sensory input
Integration
Motor output
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Figure 11.1
Organization of the Nervous System
1. Central nervous system (CNS)
• Brain and spinal cord
• Integration and command center
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Organization of the Nervous System
2. Peripheral nervous system (PNS)
• Paired spinal and cranial nerves carry messages to
and from the CNS
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Organization of the Nervous System
Peripheral nervous system
1. Sensory (afferent) division
2. Motor (efferent) division
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Organization of the Nervous System
Motor division of PNS
1. Somatic (voluntary) nervous system
2. Autonomic (involuntary) nervous system (ANS)
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• Somatic
(Conscious control of skeletal muscles)
• Autonomic (Regulates smooth muscle, cardiac
muscle, and glands)
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Autonomic
Two functional subdivisions
Sympathetic
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Parasympathetic
Confused
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Don’t worry
we will do it together
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Copyright © 2010 Pearson Education, Inc.
Before going to next slide just revise
What is histology?????
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Histology of Nervous Tissue
Two principal cell types
1. Neurons
(excitable cells that transmit electrical
signals)
2. Neuroglia cells
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A. Neuron
Excitable cells of the nervous system having two types
of processes.
1. Dendrites
2. Axons
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Bundles of processes are called
• Tracts in the CNS
• Nerves in the PNS
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Dendrites
(receptive regions)
Cell body
(biosynthetic center
and receptive region)
NEURON
Axon
Nucleus
Axon hillock
(b)
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Schwann cell
(one internode)
Axon
terminals
(secretory
region)
Figure 11.4b
NEURON
Dendrites
1. Impulse Receiving processes
2. Projects out from cell body of the
neuron
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NEURON
Axon
1. One axon per cell arising from the axon
hillock
2. Impulse sending processes
3. Long axons (nerve fibers)
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NEURON
Structural Classification of Neurons
Multipolar—1 axon and several dendrites
•
Most abundant
•
Motor neurons and interneurons
Bipolar—1 axon and 1 dendrite
•
Rare, e.g., retinal neurons
Unipolar (pseudounipolar)
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Table 11.1 (2 of 3)
NEURON
Functional Classification of Neurons
1.
Sensory (afferent)
Transmit impulses from sensory receptors toward the CNS
2. Motor (efferent)
Carry impulses from the CNS to effectors
3. Interneurons
most are entirely within the CNS
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B. NEUROGLIA CELLS
(supporting cells)
1. Astrocytes (CNS)
2. Microglia (CNS)
3. Ependymal cells (CNS)
4. Oligodendrocytes (CNS)
5. Satellite cells (PNS)
6. Schwann cells (PNS)
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Astrocytes
• Most abundant, versatile, and highly branched
glial cells
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Microglia
• Small, ovoid cells with thorny processes
• Migrate toward injured neurons
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Ependymal Cells
• Range in shape from squamous to columnar
• May be ciliated
• Line the central cavities of the brain and spinal
column
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Oligodendrocytes
• Branched cells
• Processes wrap CNS nerve fibers, forming
insulating myelin sheaths
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White Matter and Gray Matter
White matter
• Dense collections of myelinated fibers
Gray matter
• Mostly neuron cell bodies and unmyelinated fibers
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Table 11.1 (3 of 3)
Developmental Aspects of Neurons
• The nervous system originates from the neural tube
and neural crest formed from ectoderm
• The neural tube becomes the CNS
• Neuroepithelial cells of the neural tube undergo
differentiation to form cells needed for
development
• Neuroblasts sprout axons to connect with targets
and become neurons
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WOW WE DID IT
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BUT BEFORE GOING WE HAVE TO SUMMARIZE IT.
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KEYPOINTS
Organization of the nervous system
1. Central nervous system
2. Peripheral nervous system
a. Sensory division
b. Motor division
- Somatic nervous system
- Autonomic nervous system
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KEYPOINTS
Histology of nervous Tissue
• Neurons
Dendrites
Axons
Classification
• Neuroglia cells
• Gray matter & white matter
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KEYPOINTS
Neuroglia cells
•
Astrocytes (CNS)
•
Microglia (CNS)
•
Ependymal cells (CNS)
•
Oligodendrocytes (CNS)
•
Satellite cells (PNS)
•
Schwann cells (PNS)
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Developmental Aspects of Neurons
The nervous system originates from the neural tube
and neural crest formed from ectoderm
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FINALLY WE FINISHED FOR TODAY
ANY QUESTIONS????
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