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86 Cards in this Set
- Front
- Back
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What is neuropathy?
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any generic syndrome in which one or more nerves are affected by any of several known or unknown causes
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What is mononeuropathy?
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a single, major nerve is specifically involved usually due to trauma or compression; sensory and motor deficits depend on the nerve's anatomic distribution
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What is polyneuropathy (peripheral neuropathy)?
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a disorder of multiple nerves, both major and small, unnamed branches
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What are the symptoms of polyneuropathy?
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early sensory loss or impairment (distal limbs feet before hands, stocking and glove pattern, paresthesia or dysesthesia); distal limb weakness and atrophy; early loss or decrease of reflexes (often prior to weakness); autonomic symptoms if involved (orthostatic hypertension, incontinence, impotence, sweating abnormalities)
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Why does polyneuropathy begin by affecting the sensory of the most distal part of the body (feet)?
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these are the longest sensory fibers of the body
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What is the pathology of neuropathy?
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Demyelination (due to focal compression, primary cause of Guillan-Barre, if severe can cause secondary axonal degeneration); Axonal loss (degeneration of axon distal to the traumatic nerve injury, the primary process in most polyneuropathies due to metabolic problems)
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What is wallerian degeneration?
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where axons and myelin degenerate distal to the point of nerve injury in traumatic mononeuropathy
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What is the primary process in most polyneuropathies?
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axonal degeneration, possibly due to metabolic problems and inadequate axoplasmic flow; secondary demyelination may occur
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How is polyneuropathy diagnosed?
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review of family history, occupation, hobbies, and medications; clinical pattern of nerve involvement; blood and urine tests for causes; EMG to evaluate the electrical activity and function of nerves and muscles; nerve biopsy; 50-60% cause is unknown
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How is polyneuropathy treated?
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treat the underlying cause (DM, alcoholism) if found; orthotic devices for safe ambulation; physical therapy to maintain joint range of motion; medications to reduce symptoms of dysesthesia and pain
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What is dysesthesia?
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an unpleasant sensation from a nonnoxious stimulus
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What is Guillain-Barre syndrome?
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an acute inflammatory demyelinating polyradiculoneuropathy; due to an immune system attack of peripheral nerve myelin because of an antigenic similarity with a virus; affecting all ages, 50% with recent viral illness;
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What does a primary slowing of nerve conduction velocity in a nerve conduction study suggest?
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a demyelination problem
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What does a primary reduction of amplitude in a nerve conduction study suggest?
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an axonal loss
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What are symptoms of Guillain-Barre syndrome?
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an ascending (leg first) areflexic paralysis, which may become generalized and severe with respiratory paralysis; primarily motor loss with parasthesia and minimal sensory loss; progressive weakness over hours to days, usually plateauing around 2-4 weeks
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What is the pathology seen in Guillain-Barre?
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inflamed and demyelinated peripheral nerves/roots possibly with secondary axonal loss
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How is Guillain-Barre confirmed/diagnosed?
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EMG which shows demyelination of multiple nerves; elevated CSF protein with few to no WBC
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What is the treatment for Guillain-Barre syndrome?
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ICU monitoring; plasmapheresis (mechanical removal of antibodies from the blood) or gamma globulin infusions to shorten the immune attack and hasten recovery
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What is chronic acquired polyneuropathy?
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a slow development of polyneuropathy symptoms over months to years due to many causes: diabetes, metabolic/endocrine (uremia, hypothyroidism); rheumatologic dz; cancer, myeloma; infection (leprosy is the most common cause worldwide); nutritional deficiencies; toxins (alcohol, lead, solvents, drugs)
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What are hereditary polyneuropathies?
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non-curative polyneuropathies which begin in childhood and may be subtle, often present with orthopedic deformities (scoliosis, hammertoes) bc it begins when growing; caused by metabolic mechanisms or genetic disorders; treat with assistive devices
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What is myopathy?
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generic term for primary muscle disease of several types
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What are the symptoms of myopathy?
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proximal limb weakness and atrophy (where there is a lot of muscle); preservation of reflexes (lost only after severe atrophy); intact sensation; cramps/fatigue
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Which disease, polyneuropathy or myopathy, presents with distal weakness and early loss of reflexes?
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polyneuropathy
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Which disease, polyneuropathy or myopathy, presents with proximal weakness and late loss of reflexes?
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myopathy
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How are myopathies diagnosed?
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clinical symptoms, review of family history (muscular dystrophy); measure muscle enzymes (creatine kinase is often elevated in serum); EMG abnormalities; muscle biopsy
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What is polymyositis?
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inflammation of multiple muscles most often due to an autoimmune disorder; viral infections and drug reactions can also cause this
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What are symptoms of polymyositis?
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proximal weakness which progresses over weeks to months, may be accompanied by a rash around the eyes or fingers or distributed diffusely (dermatomyositis)
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What is the epidemiology of polymyositis?
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occurs btw 30-60 years of age; 2 females:1 male; rarely associated with an underlying carcinoma (esp small cell lung carcinoma); biospy shows mononuclear inflammatory cells and muscle fiber necrosis
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What is the treatment for polymyositis?
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corticosteroids and other immunosuppressants (azathioprine, cyclophosphamide, methotrexate)
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What is muscular dystrophy?
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several different types of variably progressive inherited myopathies, severe types are obvious in childhood, while subtle types can go unnoticed into adulthood
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What is Duchenne's muscular dystrophy?
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an X-linked disease caused by a break in the short arm of the X chromosome which leads to a deficiency in dystrophin (structural protein) in muscle; results in calf pseudohypertrophy, proximal weakness, cardiac involvement; usually results in death by the third decade of life from respiratory weakness
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What are types of muscular dystrophy other than Duchenne's?
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facioscapulohumeral; oculopharyngeal; limb-girdle are restricted to fewer muscles
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What is myotonic dystrophy?
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autosomal dominant defect of chromosome 19 (multiple trinucleotide repeats) causing abn muscle membrane ion channels; leading to distal and proximal weakness, myotonia, cateracts, frontal baldness, testicular atrophy, low IQ, cardiac arrhythmias, treated with meds to alleviate myotonia but not weakness
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What is myotonia?
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the impaired relaxation of a muscle after percussion or contraction, due to abnormally phosphorylated muscle membrane ion channels
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What are some lower motor neuron specific disorders (due to anterior horn cells)?
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infantile (Werdnig-Hoffman) spinal muscular atrophy with fatal outcome; childhood and adult spinal muscular atrophy (Kugelberg-Welander); adult benign focal amyotrophy which involves one limb (has best prognosis and normal life span)
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What are some upper motor neuron specific disorders?
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primary lateral sclerosis; progressive bulbar palsy; pseudorbulbar palsy
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What is primary lateral sclerosis?
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involves corticospinal tracts, no structural or metabolic cause; UMN signs (weakness, spasticity, hyperreflexia, babinski); may be familial
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What is progresive bulbar palsy?
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degeneration of pons and medulla motor nuclei (CN V, VII, IX, X, XII)
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What is pseudobulbar palsy?
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involves corticobulbar tracts, possibly due to bilateral strokes or brain tumors, UMN signs of facial weakness, dysarthria, dysphagia, and hoarseness
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What is amyotrophic lateral sclerosis?
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most common motor neuron disease, yet has the worst prognosis; both UMN and LMN degeneration
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What is the epidemiology of ALS?
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4-6/100,000; 2males:1female; symptom onset btw 40-70 yo; rare familial or associated with dementia and parkinsonism; 50% of pts die within 3 years of diagnosis due to respiratory failure
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What are signs/symptoms of ALS?
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regional weakness and atrophy of a limb which spreads and becomes bilateral; diffuse fasciculations; progressively involves all motor neuron subgroups leading to hyperreflexia, spasticity, or babinski, affects speech, chewing, swallowing, and breathing; spare eye muscles, bowel and bladder control; sensation remains intact
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What is the pathology seen in ALS?
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neurogenic atrophy of muscle; gliosis and loss of anterior horn cells, pyramidal neurons; degeneration of corticospinal and corticobulbar tracts
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How is ALS diagnosed?
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clinical features; EMG showing widespread subclinical motor denervation and reinnervation; exclusion of other toxic causes, if prominent LMN signs in upper limbs with UMN signs in lower limb then must r/o cervical spinal cord lesion
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What is the treatment for ALS?
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no curative; riluzole (glutamate antagonist) prolongs survival
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What is neurulation?
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formation of the neural tube from the neuroectoderm, closure of the neural tube and formation of the primitive brain and spinal cord
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What are three characteristics of the neural plate?
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polarity; bilateral symmetry; regionalization
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What is necessary for the formation of the polarity, bilateral symmetry and regionalization of the neural plate?
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requires neural patterning that endow the precursor cells with the ability to give rise to the correct type of neuron in the right location
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What is neural induction?
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the induction of neural ectoderm from ectoderm which by default forms epidermis; the secretion of BMP inhibitors by the dorsal mesoderm (neural organizer) signals the formation of the neural ectoderm rather than epidermis
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How do neural cells change throughout the proliferative, differentiation, and migratory stages of neural development?
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changes in patterns of gene expression in a progressive, wave-like manner for the proper cell types to be formed in the proper regions/stages of development
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What two things control the neural fate of cells?
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extrinsic determinants (a source sends a signal which drives the fate of cells via paracrine/autocrine signal transduction pathways and subsequent changes in gene expression); intrinsic determinants (genes that are turned on/off and the pattern of which are passed on to daughter cells in the lineage and not affected by external signals)
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What are three different directions of migration in neural development?
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1st: Anterior-posterior (via differential gene expression); 2nd: Dorsal-ventral (via extrinsic gradient of SHH concentration); 3rd: Radial (along the glial cells)
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How is the dorsal-ventral axis of neural development controlled?
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via the notochord secretion of the sonic hedgehog (SHH) which is in high conc. Ventrally and signals the induction of motor neurons and in low conc. Dorsally and signals the induction of sensory neurons
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How do neuroblasts migrate radially?
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along radial glial fibers laterally
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How are axons of neuroblasts guided in their growth?
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push-pull-hem method: chemorepulsive signals push the axons away; chemoattractive molecules pull the axons towards (this gradient sets up longitudinal axis) and short range cues/signals prevent lateral motion and "hem"
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What is synapse matching?
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the molecular cues from presynaptic nerve terminals (ie Agrin in motor neuron) must match with post synpatic signals (ie. AchR clusters on muscle); to form the proper link and formation of a neuromuscular junction or proper synapse
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What is programmed cell death and its role in neural development?
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too many neurons are made during the development of the nervous system, there is spatiotemporal cell loss/patterning (via genetic and environmental factors) to "prune" the system, dependent on signals from cell to cell interactions and external, neurotrophic factor exposure (which promotes survival)
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What results from an aberration in the balance btw neural development and programmed cell death?
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cancer if no response to or no signal for programmed cell death signals (glioma, neuroblastoma); or neurodegeneration if too much neural cell death occurs (ie. ALS)
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What is synapse elimination?
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transient, redundant/overlapping synapses are formed during neural development which are replaced with adult circuitry that is unique and functionally distinct such as multiple neural connections to a single m. fiber develops into a single innervation per muscle fiber
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What major steps must occur for proper neural patterning (spatial ordering)?
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neural induction (BMPs); cellular determination (intrinsic and extrinsic); migration (AP, DV, radial); connectivity (push-pull-hem of axons; synapse matching); regressive events (programmed cell death); influence of genetics and activity of neurons
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What is the critical period of neural development?
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a period of time that synaptic connections pass through in early life during which the capacity to adjust to environmental stimuli/experiences is great and can modify the neural pathways/connections formed (esp binocular vision, language, social imprinting)
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What process mimics neural development?
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regeneration recapitulates development (ie. axonal growth and synaptic matching during neuronal damage and repair); follows intrinsic and extrinsic signals
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What are symptoms of a brain tumor?
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slower onset of symptoms than stroke; specific, localizable syndrome; seizures; increased ICP; impaired mental function
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What are presenting symptoms in children with cerebellar tumors?
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vomiting (area postrema); hydrocephalous; HA; cerebellar ataxia (Triad: vomiting, HA, papilledema)
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What are pediatric pitfalls or very bad signs in kids with a head trauma?
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blood loss is lethal; tachycardia; <1 year of age; hyperthermia
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What is the most common diffuse cerebral injury?
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cerebral contusion, 2x as common in children with 53% mortality rate
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What is one of the most important things to consider during a traumatic brain injury?
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oxygenation and perfusion of the brain in the first minutes after injury is essential
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Where is regeneration of neurons more successful?
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peripherally not centrally
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What is neuroregeneration?
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regrowth of a damaged axon
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What is neuro plasticity?
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remodeling of spared, uninjured neural pathways to compensate for region that lost innervation; shows the flexibility and adaptability of the nervous system; is experience related
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What is anterograde degeneration response to nerve injury?
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wallerian degeneration: axon breaks down and myelin breaks down; mediated by macrophages and the innate immune system
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What is retrograde degeneration response to nerve injury?
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the cell body swells, Nissl substance is lost due to ribosomes falling off the RER due to changes in the protein expression in the neuron (chromatalysis)
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What is beneficial about Wallerian degeneration following axonal injury?
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the degeneration creates a growth permissive environment which allows for regeneration to be more successful
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What changes occur in the cell body of a neuron after axonal injury?
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↑rRNA and mRNA →↑ribosomes and protein synthesis→↑production of regeneration-associated proteins/genes (ie. tubulin for length and neurofilaments for radial growth)→↑axonal elongation and synaptogenesis
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Why is regeneration more successful in the PNS vs. the CNS?
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the extrinsic determinants are different and within the CNS they are inhibitory and prevent axonal growth
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What are the positive and negative effects astrocytes/glia can have during neuronal trauma?
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positive: play a role in normal neuronal metabolism, astrocytes provide metabolic support (growth factors, adhesion molecules, spatial buffering, protection from excitotoxicity), microglia modulate the immune response; schwann cells produce a growth permissive environment; Negative: can proliferate and form a glial scar esp in the spinal cord and prevent axonal regeneration
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What substance produced by oligodendrocytes inhibits the regeneration of axons within the CNS environment?
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Nogo-A
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Are old or young neurons more likely to die from trauma?
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young neurons are more vulnerable to injury, yet they are better able to undergo plasticity to regain function
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Is proximal or distal nerve trauma more severe?
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more proximal to the cell body is more severe and is more likely that the neuron will die
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What level does neural plasticity occur at?
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primarily at connectivity points (ie formation of synapses); results in alternate pathways for various NS functions
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What is collateral sprouting?
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the growth/sprout of an axon off of a viable, uninjured peripheral neuron near a damaged axon; axon sprout reinnervates denerveated muscles peripherally at the vacated synapse sites; results in a giant motor unit
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What is synaptic reclaimation?
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collateral sprouting within the CNS results in nearby viable neurons forming synpases at the vacated sites previously occupied by a damaged neuron; may form maladaptive alternative pathways
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What protein is the most important in inducing neurite inhibiton?
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Nogo-A which acts at Nogo-66 receptor to activate p75 and downstream rxns to cause neurite inhibition
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What molecules are responsible for creating an inhibitory regenerative environment in the CNS?
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Nogo-A; MAG; OmgP; proteoglycans
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What can be used to block Nogo-A and help to promote new axonal sprouting in the CNS after a stroke?
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IN-1, monoclonal antibody which neutralizes Nogo-A and prevents its inhibitory function
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What environmental enrichment changes can enhance neuronal plasticity and improve functional recovery?
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social interactions; complex housing; regimented physical therapy
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