Nervous TissueQuickTime™ and a decompressor

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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!