Transcript Nervous Tissue: Support Cells

Nervous Tissue:
Neuroglia = Support Cells
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Support cells in the Central
Nervous System (CNS) are
grouped together as neuroglia
Neuroglia literally means
“nerve glue”
The function of neuroglia is to
support, insulate, and protect
the delicate neurons of the
brain
Types of
Neuroglia
in CNS
 Astrocytes
– Star-shaped cells
– Half of all brain tissue
– Brace neurons; they keep
the neurons in contact with
their blood supply (capillaries)
– Control the chemical environment
of the brain by mopping up leaked
ions
Types of
Neuroglia
in CNS
 Microglia
– Spiderlike phagocytes
(white blood cells)
– Dispose of debris like
dead brains cells and
bacteria
Types of Neuroglia in CNS
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Ependymal cells
– Lines the cavities of the brain and spinal cord
– Circulate cerebrospinal fluid by beating their cilia
– Cerebrospinal fluid fills the space the brain does
not take up and forms a protective cushion
around the brain and spinal cord
Types of
Neuroglia
in CNS
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Oligodendrocytes
– Wrap around nerve cells in
the brain and spinal chord
– Produce myelin sheaths for
spinal cord and brain (CNS)
– Myelin is a fatty, insulation
covering the nerve cells;
allows for the electrical signal
to transmit faster (like wire
coating)
Types of Neurolgia in PNS
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Schwann cells
– Form myelin sheath in the peripheral
nervous system (nerves of the body;
not nerves of the CNS)
So what’s a Neuron?
 Neurons
are nerve cells
– Cells specialized to
transmit messages
– Major parts of neurons
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Cell body — nucleus and
metabolic center of the cell
(main part of nerve cell)
Processes — fibers that
extend from the cell body
(where messages sent or
received)
– can be microscopic or up to
3-4 feet in length
Anatomy of a Neuron
 Cell
body
– Nucleus
 Processes
cell body
outside the
– Dendrites — send
impulses toward the
cell body
– Axons — send
impulses away from
the cell body
Anatomy of a
Neuron
 Axons
end in axon
terminals
 Axonal terminals contain
small sacs with neurotransmitters
(chemicals)
Synapse and
Synaptic Cleft
 Axonal
terminals are
separated from the
next neuron by a gap
(they never really
touch)
– Synaptic cleft — gap
(space) between
adjacent neurons
– Synapse — junction
between nerves
What happens at
a synapse?
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For communication
between neurons to occur,
an electrical impulse must
travel down an axon to the
synaptic terminal.
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The neurotransmitter
diffuses across the
synaptic cleft .
They bind with receptor sites on
the other neurons’ dendrite.s
This influences the electrical
response in the neuron.
If enough neurotrasmitter is
released, it changes the cell's
excitability
This allows for the signal to move
on to the next neuron
Multiple
Sclerosis
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MS affects the ability
of nerve cells in the
brain and spinal cord
to communicate with
each other.
In MS, the body's
own immune system
attacks and damages
the myelin