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20 Cards in this Set
- Front
- Back
What does a motor unit consist of?
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LMN (anterior horn or cranial nerve nucleus)
Axon Innervated muscle fibers |
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What is the role of Schwann cells?
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Provide myelin for the PNS - myelin composed of 2 layers of fused Schwann cell membrane
Death of axon results in myelin breakdown but Schwann cell remains viable (if myelin is lost axon is not disrupted) |
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What is the epineurium?
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Loose connective tissue binding fascicles into single nerve trunk, contains majority of vascular supply
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What is the perineurium?
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Connective tissue that is circularly arranged around each fascicle & contains tight junctions restricting entry of foreign material into endoneurium - blood nerve barrier
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What is the endoneurium?
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Interstitial connective tissue w/in fascicles & outside the axon-Schwann cell units
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What kind of technique should be used to identify axonal degeneration vs. sedmental demyelination in long lengths of nerve fibers?
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Teased fiber preparation
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What is a neuronopathy or axonopathy?
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Generalized abnormality affecting neuronal cell body or axon which manifests as dying back of distal portion of axon (example: motor neuron disease)
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What is chromatolysis?
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Swelling of neuron cell body w/ peripheral displacement of nucleus & Nissl substance
Occurs with direct axonal injury close to neuron |
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What is Wallerian degeneration?
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Results when axonal injury occurs because of a focal lesion such as trauma (commonly transection)
Distal portion of fiber (axon & myelin) undergoes degeneration |
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What are myelin ovoids or digestion chambers?
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Occur in either Wallerian degeneraton or a neuronopathy/axonopathy
Axon & myelin break down, Schwann cells proliferate & catabolize myelin |
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What is segmental demyelination?
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Occurs with primary dysfunction/damage of Schwann cells or primary damage to myelin sheath, but NO primary abnormality of axon
Causes conduction block or marked slowing but NO chromatolysis Schwann cells replaced & axons remyelinated |
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What are the consequences of segmental demyelination over time?
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With sequential demyelination & remyelination Schwann cell processes accumulate & form concentric circles of cytoplasm & basement membrane known as onion bulbs
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følge (fulgte, fulgt)
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follow
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What is the clinical presentation of Guillan-Barre syndrome?
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Progression over hours to days of symmetric weakness & areflexia
May extend to involve face, bulbar, respiratory muscle Most often presents as ascending paralysis, prominent sensory loss is rare |
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What is chronic demyelinating polyneuritis?
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Resembles GBS but has less acute presentation & recovery & recurs frequently
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What is the clinical pattern of vasculitic neuropathy?
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May see distal symmetric sensorimotor polyneuritis (common pattern for lupus) or mononeuropathy multiplex (common pattern for polyarteritis nodosa)
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What is the most common treatable neuropathy in the world?
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Leprosy
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What are some peripheral neuropathies accompanying inherited metabolic disorders?
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Adrenoleukodystrophy
Familial amyloid polyneuropathies Porphyria Refsum disease |
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What is the most common hereditary peripheral neuropathy?
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Hereditary motor & sensory neuropathy I (Charcot-Marie-Tooth, hypertrophic form or Peroneal Muscular Atrophy)
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What is the most common sarcoma of adulthood?
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Liposarcoma
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