Transcript Nervous Tissue - NHSAdvancedBiology

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Nervous Tissue
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Neuroglia “Nerve Glue”
(Support Cells)
• Neuroglia - nonconductiong cells that
provide protection & support
and assist with metabolism
Neuroglia “Nerve Glue”
(Support Cells)
Neuroglia “Nerve Glue”
(Support Cells)
• Oligodendrocytes - form the myelin
sheaths, which wrap
around neurons in
the CNS to protect &
insulate
• Schwann cells - form the myelin sheaths &
neurilemma in neurons of the
PNS
Neuroglia “Nerve Glue”
(Support Cells)
• Microglia - spider shaped phagocytic
cells of CNS; engulf & digest
bacteria, foreign objects & dead
cells
• Astrocytes - star shaped cells that help
maintain the blood-brain
barrier
Neuroglia “Nerve Glue”
(Support Cells)
• Ependymal Cells - line cavities of the CNS
and have cilia which help
to circulate cerebrospinal
fluid (CSF)
Glial Cells Activity
Neuron Video Clip
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Neurons (nerve cells)
• Neuron - structural & functional unit of
nervous tissue; cell body with
many extensions or processes
(nerve “fibers”) which conduct
impulses
Neurons (nerve cells)
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Neuron Structure
• Cell body (soma) - metabolic center of
the neuron; contains the
nucleus, neuroplasm &
organelles such as Nissl
bodies (rough ER for protein
synthesis) and neurofibrils
(provide support & transport
proteins
-Does not contain centrioles; neurons
cannot divide (reproduce)
Neuron Structure
• Dendrites - short, numerous, and thickly
branched extensions of the cell body
(like tree roots)
-Receive messages from other neurons
and conduct the impulses toward the
cell body = afferent process
Neuron Structure
• Axon - single, long, cylindrical tube with
the same consistent diameter,
runs through and out of the cell
body(like a tail). End has many
fine branches.
-Carries impulses away from the cell
body to another neuron or effector cell
(muscle or gland) = efferent process
Other Parts of a Neuron
• Myelin sheath - pearly white, shiny lipid
substances that cover the axon of many
neurons; protects, insulates, & allows
for faster conduction of impulses
• Neurilemma - delicate covering over
myelin sheath (made by Schwann cells
in PNS neurons); helps to repair
damaged nerve processes
Other Parts of a Neuron
• Axis cylinder - central core of a nerve
fiber - part which impulse travels down
• Nodes of Ranvier - indentations in the
myelin sheath; important in the
conduction process
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What is the difference
between a neuron & a nerve?
• Neuron = an individual nerve cell
capable of conducting impulses
• Nerve = a group of individually insulated
nerve cell fibers
Nerve Structure
Individual nerve fiber wrapped by
endoneurium -->
Fascicle (group of nerve fibers)
wrapped by perineurium -->
Nerve (cord-like) wrapped by
epineurium
Nerve Structure
White vs. Grey Matter
• White matter - nervous tissue that has a
myelin sheath
-mainly consists of axons & found in
outer portion of spinal cord and
inner part of brain
White vs. Grey Matter
• Grey matter - nervous tissue that lacks
a myelin sheath
-mainly consists of cell bodies on
outer surface of brain & central
portion of spinal cord
White vs. Grey Matter
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Classification of Neurons
• Structural - # of processes = unipolar,
bipolar, multipolar
• Functional - sensory, motor, or
associative
Classification of Neurons
Types of Nerves
• Mixed - carry both sensory & motor
fibers (like a two way street)
• Afferent (sensory) - carry only sensory
fibers [like a one-way street to the
brain/spinal cord]
• Efferent (motor) - carry only motor fibers
[like a one way street from the
brain/spinal cord]
Video Clip: Nerve Types
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The End!