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Jan 03, 2016
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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)
• 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
Neurons (nerve cells)
• Neuron - structural & functional unit of
nervous tissue; cell body with
many extensions or processes
(nerve “fibers”) which conduct
impulses
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
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
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
Classification of Neurons
• Structural - # of processes = unipolar,
bipolar, multipolar
• Functional - sensory, motor, or
associative
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]