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Nervous Tissue
College of Medical Laboratory Science
OUTLINE
I
...
III
...
Introduction
Membrane Potential
Development of the Nerve Tissue
Cells of the CNS & PNS
A
...
According to the number of processes
2
...
Neuroglia
1
...
Astrocytes
2
...
Ependymal cells
4
...
PNS Neuroglia
1
...
Satellite cells
Nerve tissues
• Formed by a network of many billion nerve cells
(neurons) & assisted by many more supporting
GLIAL cells
...
CNS : brain & spinal cord
2
...
Nerve cells/ Neurons
– Functional unit/ cell of the nervous
system
– Usually show numerous long processes
– Coordinate the functions of other organ
systems
B
...
• All cells maintain such gradient (ELECTRICAL POTENTIAL)
but cells rapidly change this potential in response to
stimuli/ reversal of the ionic gradient (MEMBRANE
DEPOLARIZATION)>>> propagation of this phenomenon
is called action potential/ depolarization wave/ nerve
impulses>>> transmission of signals to other cells>>>
continuous stabilization of the intrinsic condition of the
body
• Eq
...
Ectoderm
2
...
3
...
Neural tube detaches from
ectoderm ; produces mass of
messenchymal cells called
Neural Crest (ENTIRE PNS)
Development of Nerve Tissue
Ectoderm > Neural plate > Neural tube > CNS including its cells
A
...
Classification of neurons according to the number of
processes:
1
...
Bipolar neurons: 1 axon and 1 dendrite
3
...
: 1 axon and 2 branches
A
...
Division of neurons according to function:
a
...
b
...
A
...
• Contain highly developed rough ER
• -RER & free ribosomes appear under light
microscope as clumps of basophilic material called
Nissil bodies (synthesizes neurotransmitters)
• Neurofilament, intermediate filaments found in
perikarya
...
- yellow-brown pigment granules (lipid containing
residues)
B
...
• “Dendron” = tree
• Dendritic spines
– Where most synapses impinging on neurons
are located
...
•
C
...
Terminal boutons (end bulb): dilation of terminal arborization
...
•
•
•
•
•
Axon hillock
– Pyramid shaped region where all axons originated, arising from the perikaryon
...
(decision to propagate or not a nerve impulse)
...
ANTEROGRADE TRANSPORT
– Organelles and macromolecules synthesize in the
cell body
– Move along the axon from the perikaryon to the
synaptic terminals
*KINESIN: microtubule-activated ATPase
B
...
• Presynaptic cell VS
...
Neuromodulator
Neurotransmitter
– chemicals that bind specific receptor proteins to either open or closed
ion channels
...
– Removal of neurotransmitters is functionally important because it
prevents on undesirable sustained stimulation of the post synaptic
neurons
– Ex: acetylcholine- activates muscle, autonomic nervous system
Neuromodulator
– chemical messengers that modify neuron sensitivity to synaptic
stimulation/ inhibition without acting directly on synapses
...
Presynaptic axon terminal (terminal bouton)
– from which neurotransmitter is released
b
...
c
...
Morphological variation of synapse
• Axosomatic synapse
• Axodendritic
• Axoaxonic
Myeline sheath: insulator, electical impulses cant pass, assoc
only with axons
Nodes of ranvier: unmyelinated area around the axon
...
Neuroglia/ Glial cells
• Supportive cell of the nervous system
• 10x more abundant than neurons
...
CNS Neuroglia
1
...
– Most numerous glial cells in CNS gray matter
– Exhibit considerable morphologic & functional diversity
...
– Regulate vasodilation & transfer of O2 ions & other substances from
blood to the neurons
...
Two Types of Astrocytes:
a
...
Fibrous astrocytes
– Found in the white matter
– Long and thin
CNS Neuroglia
2
...
– “Predominant glial cell in CNS white matter”
...
EPENDYMAL CELLS
– Low columnar cells/ cuboidal that line the ventricles of
the brain & central canal of the spinal cord
...
– Joined apically by junctional complexes
...
Instead, the basal ends of ependymal cells are elongated
& extend branching processes into the adjacent
neuropil
...
MICROGLIAL CELL
– More evenly distributed throughout gray & white
matter
...
– Secrete number of immunoregulatory cytokines
& constitute the major mechanism of defense in
CNS tissue
...
PNS Neuroglia
1
...
2
...