Term
| What is the role of glial cells? |
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Definition
| Bind neurons together and provide a supportive framework for nervous tissue |
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Term
| Are there more neurons or glial cells in the body? |
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Definition
| Glial cells - outnumber about 50 to 1 |
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Term
| Wherever a mature neuron is not in synaptic contact with another cell, it is covered in what? |
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Definition
|
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Term
| What are the four types of neuroglia (glial cells) in the CNS? |
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Definition
1 - Oligodendrocytes
2 - Ependymal cells
3 - Microglia
4 - Astrocytes |
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Term
| What is the main function of oligodendrocytes? |
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Definition
| To provide support to axons and to produce the Myelin sheath, which insulates axons. |
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Term
| How are ependymal cells different to true epithelial cells? |
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Definition
| Have no basement membrane - exhibit root-like processes - penetrate into underlying tissue |
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Term
| What types of cells do ependymal cells resemble? |
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Definition
| Cuboidal epithelium cells |
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Term
| What area of the body fo ependymal cells line? |
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Definition
| The internal cavities of the spinal cord and brain |
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Term
| What type of cells produce cerebrospinal fluid (CSF)? |
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Definition
|
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Term
| How do ependymal cells help circulate the CSF that they produce? |
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Definition
| Have patches of cilia on their apical surfaces - helps circulate CSF |
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Term
| What types of cells are microglia? |
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Definition
| Small macrophages that develop from monocytes |
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Term
| What type of glial cells are small macrophages that develop from monocytes |
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Definition
|
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Term
| What is the function of microglia? |
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Definition
| Wander through CNS looking for debris and other problems and perform complete checkup of brain several times a day |
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Term
| Pathologists may look for microglia cells as clues to what? |
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Definition
| Sites of injury - microglial cells become concentrated in areas of stroke, infection, or trauma |
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Term
| What type of glial cells become concentrated in areas of stroke, infection, or trauma? |
|
Definition
|
|
Term
| What is the most abundant type of glial cell? |
|
Definition
|
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Term
| Astrocytes cover what area of the body? |
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Definition
| The entire brain surface and most synaptic regions of neurons in grey matter of CNS |
|
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Term
| What gives astrocytes their name? |
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Definition
|
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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? |
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Definition
|
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Term
| What are the two types of glial cells in the PNF? |
|
Definition
| Schwann Cells and Satellite Cells |
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|
Term
| What is the function of Schwann cells? |
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Definition
| Envelop nerve fibers, most producing a myelin sheath, and assisting in regeneration of damaged fibers |
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Term
| Satellite cells are found where? |
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Definition
| Surrounding neurosomas in ganglia of PNS |
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|
Term
| What is the function of satellite cells? |
|
Definition
| Provide electrical insulation around soma, and regulate chemical environment of the neurons |
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|
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
|
|
Term
| Is myelin mainly made from protein or lipid? |
|
Definition
| Lipid - makes 80%, protein is only 20% |
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|
Term
|
Definition
| The production of myelin sheath |
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|
Term
| In the PNS, do schwann cells spiral inward or outward? |
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Definition
|
|
Term
| In the CNS, where does the myelin sheath end? |
|
Definition
| In the neurilemma - the thick outermost coil |
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|
Term
|
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
|
|
Term
| What is external to the basil lamina? |
|
Definition
| Endoneurium - a thin sleeve of fibrous connective tissue |
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|
Term
|
Definition
| A thin sleeve of fibrous connective tissue, external to the basil lamina of a myelin sheath |
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|
Term
| Why can oligodendrocytes spiral like Schwann cells? |
|
Definition
| They are anchored to multiple nerve fibers |
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|
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 |
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|
Term
| What are the gaps between the segments of myelin called? |
|
Definition
|
|
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 |
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|
Term
|
Definition
| Myelin covered segments that from between one gap (node of Ranvier) to the next |
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|
Term
| What is the initial segment on a nerve cell? |
|
Definition
| Short section of nerve fiber between axon hillock and first glial cell |
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|
Term
| What is the collective name given to the axon hillock and initial segment? |
|
Definition
|
|
Term
| In the PNS, even unmyelinated nerve fibers enveloped in what type of cells? |
|
Definition
|
|
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 |
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|
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 |
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|
Term
| If larger, myelinated fibers carry conduction the fastes, why aren't all nerves large and myelinated? |
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Definition
| The nervous system would be impossibly bulky or limited to far fewer fibers |
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|
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 |
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|
Term
| Are nerve fibers of the PNS or CNS more vulnerable to injury? |
|
Definition
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|
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 |
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|
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
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