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Supportive Cells (Neuroglia or Glial Cells)
Overview
52
Anatomy
Undergraduate 1
03/13/2013

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Cards

Term
What is the role of glial cells?
Definition
Bind neurons together and provide a supportive framework for nervous tissue
Term
Are there more neurons or glial cells in the body?
Definition
Glial cells - outnumber about 50 to 1
Term
Wherever a mature neuron is not in synaptic contact with another cell, it is covered in what?
Definition
Glial cells
Term
What are the four types of neuroglia (glial cells) in the CNS?
Definition
1 - Oligodendrocytes
2 - Ependymal cells
3 - Microglia
4 - Astrocytes
Term
What is the main function of oligodendrocytes?
Definition
To provide support to axons and to produce the Myelin sheath, which insulates axons.
Term
How are ependymal cells different to true epithelial cells?
Definition
Have no basement membrane - exhibit root-like processes - penetrate into underlying tissue
Term
What types of cells do ependymal cells resemble?
Definition
Cuboidal epithelium cells
Term
What area of the body fo ependymal cells line?
Definition
The internal cavities of the spinal cord and brain
Term
What type of cells produce cerebrospinal fluid (CSF)?
Definition
Ependymal cells
Term
How do ependymal cells help circulate the CSF that they produce?
Definition
Have patches of cilia on their apical surfaces - helps circulate CSF
Term
What types of cells are microglia?
Definition
Small macrophages that develop from monocytes
Term
What type of glial cells are small macrophages that develop from monocytes
Definition
Microglia
Term
What is the function of microglia?
Definition
Wander through CNS looking for debris and other problems and perform complete checkup of brain several times a day
Term
Pathologists may look for microglia cells as clues to what?
Definition
Sites of injury - microglial cells become concentrated in areas of stroke, infection, or trauma
Term
What type of glial cells become concentrated in areas of stroke, infection, or trauma?
Definition
Microglia
Term
What is the most abundant type of glial cell?
Definition
Astrocytes
Term
Astrocytes cover what area of the body?
Definition
The entire brain surface and most synaptic regions of neurons in grey matter of CNS
Term
What gives astrocytes their name?
Definition
They look like stars
Term
Forming a supportive framework for nervous tissue, stimulating the production of the blood brain barrier, convert blood glucose to lactate to supply neurons with nourishment, and secreting nerve growth factors are some of the functions of which type of glial cell?
Definition
Astrocytes
Term
What are the two types of glial cells in the PNF?
Definition
Schwann Cells and Satellite Cells
Term
What is the function of Schwann cells?
Definition
Envelop nerve fibers, most producing a myelin sheath, and assisting in regeneration of damaged fibers
Term
Satellite cells are found where?
Definition
Surrounding neurosomas in ganglia of PNS
Term
What is the function of satellite cells?
Definition
Provide electrical insulation around soma, and regulate chemical environment of the neurons
Term
Myelin is formed by which type of cells?
Definition
Oligodendrocytes in CNS, Schwann cells in PNS
Term
What is myelin made up of?
Definition
20% protein, 80% lipid
Term
Is myelin mainly made from protein or lipid?
Definition
Lipid - makes 80%, protein is only 20%
Term
What is myelination?
Definition
The production of myelin sheath
Term
In the PNS, do schwann cells spiral inward or outward?
Definition
Outward
Term
In the CNS, where does the myelin sheath end?
Definition
In the neurilemma - the thick outermost coil
Term
What is the neurilemma?
Definition
The thick outermost coil of the myelin sheath that contains the nucleus and most of cytoplasm
Term
What is external to the neurilemma?
Definition
Basil lamina
Term
What is external to the basil lamina?
Definition
Endoneurium - a thin sleeve of fibrous connective tissue
Term
What is the endoneurium?
Definition
A thin sleeve of fibrous connective tissue, external to the basil lamina of a myelin sheath
Term
Why can oligodendrocytes spiral like Schwann cells?
Definition
They are anchored to multiple nerve fibers
Term
What is the difference between the neurilemma and endoneurium in Schwann cells and oligodendrocytes?
Definition
Oligodendrocyte nerve fibers have no neurilemma or endoneurium
Term
How does an oligodendrocyte create a new layer of myelin?
Definition
Must push newer layer of myelin under old ones
Term
What are the gaps between the segments of myelin called?
Definition
Nodes of Ranvier
Term
Why do nerve fibers of both the CNS and PNS need many glial cells?
Definition
Nerve fiber is much longer than the reach of single glial cell
Term
What are internodes?
Definition
Myelin covered segments that from between one gap (node of Ranvier) to the next
Term
What is the initial segment on a nerve cell?
Definition
Short section of nerve fiber between axon hillock and first glial cell
Term
What is the collective name given to the axon hillock and initial segment?
Definition
Trigger zone
Term
In the PNS, even unmyelinated nerve fibers enveloped in what type of cells?
Definition
Schwann cells
Term
The conduction speed of nerve fibers depends on what two factors?
Definition
The diameter of the fiber, and the presence or absence of myelin
Term
If signal conduction is not deep within the axoplasm, where along a nerve fiber does it travel?
Definition
Along the surface of fiber
Term
Why do larger fibers conduct nerve signals quicker than smaller ones?
Definition
They have a higher surface area, signals travel along the surface of a fiber, thus signals conducts more rapidly
Term
If larger, myelinated fibers carry conduction the fastes, why aren't all nerves large and myelinated?
Definition
The nervous system would be impossibly bulky or limited to far fewer fibers
Term
What type of processes are suited to smaller, unmyelinated fibers?
Definition
Processes where quick responses not particularly important - eg secreting stomach acid, dilating pupils
Term
Are nerve fibers of the PNS or CNS more vulnerable to injury?
Definition
PNS
Term
Why are nerve fibers of the CNS less vulnerable to injury than those in the PNS?
Definition
Nerves in the CNS enclosed in bone
Term
What is needed for a nerve of the PNS to be able to regenerate?
Definition
The soma must still be intact and at least some neurilemma remains
Term
In what ways is the regeneration of PNS nerve fibers not perfect?
Definition
Some nerve fibers connect to wrong muscle fiber or never find muscle fiber
Term
How to damaged nerve fibers of the CNS regenerate?
Definition
They cannot
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