ms Lecture 5

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  1. How do you call diseases of
    a) Nervous tissue
    b) NMJ
    c) Muscle
    • a) neuropathies
    • b) myasthenia gravis/syndrome
    • c) myopathies
  2. Motor unit functional components
    • ⋅MN cell body
    • ⋅MN axon
    • ⋅NMJ, synapses
    • ⋅Muscle fibres
  3. General features of neurogenic and myopathic diseases (see on notes sheet)
    No answer given
  4. Fasciculation VS Fibrillation
    • Fasciculation = small visible muscle twitches (single MUs firing)
    • Fibrillation = small spontaneous twitches of single muscle fibres, not visible, require EMG analysis.
  5. A patient has distal limb weakness and fibriallations. Neurogenic or myopathic?
    Neurogenic : Myopathic would include proximal limb weakness.
  6. LOWER MOTONEURONES (LMNs) + Lesion effects
    • ⋅Primary MNs
    • ⋅Innervated skeletal muscle directly
    • ⋅Located in spinal cord ventral horn/ cranial nerve nuclei
    • Lesion: weakness, atrophy, ↓ tendon reflexes,  ↓ tone, fasciculation
  7. UPPER MOTONEURONES (UMNs) + Lesion effects
    • ⋅Originate in higher motor centre (eg. celebral cortex)
    • ⋅Synapse with LMN
    • ⋅Relay descending commands
    • Lesion : Weakness, (no paralysis, no/little citrophy), ↑ tendon reflexes, ↑ tone (spasticity), Babinski (extensor plantor responses)
  8. What does the presence of both LMN and UMN lesion signs indicate?
    Amyotrophic lateral sclerosis (LGU Gehrig disease; motor neurone disease)
  9. Tests to distinguish Neurogenic & myogenic diseases
    • ⋅Measurement of muscle enzymes in serum.
    • ⋅Electromyography
    • ⋅Nerve conduction studies
    • ⋅Muscle biopsy
    • ⋅DNA analysis
    • ⋅ Cell membrane integrity is lost in diseased/ damaged muscle cells
    • ⋅Soluble enzymes in sacroplasm leak out and can be detected in serum
    • Neuopathy - Small increase in enzyme serum
    • Myopathy - Large increase in serum enzyme
  11. Examples of enzymes that can be detected via serum enzyme measurement
    • - Creatine kinase (CK)
    • - Serum glutamic-oxaloacetic transaminase (SGOT)
    • - Lactate dehydrogenase (LDH)
  12. Electromyography (in diagnosis of neurogenic/myopatic disease)
    • Action potentials of single or groups of neighboring motor units using intramuscular electrodes
    • Main measurements:
    • -spontaneous activity at rest
    • -number of MUs under voluntary control
    • -duration & amplitude of motor unit APs
  13. Electromyography : Normal muscle
    • ⋅ No spontaneous activity at rest
    • ⋅ During weak voluntary contraction a series of MU potentials are recorded.
    • ⋅ in fully active muscles, potentials overlap so much that it's impossible to identify single potentials.
  14. Electromyograph: Diseased (neurogenic)
    • ⋅ Denervated muscle is spontaneously active at rest
    • ⋅ Muscle MAY still contract
    • ⋅ Reduced interference pattern (possible MN loss)
    • ⋅ Gian potentials -> remaining motor neurones contact more muscle fibres than normal.
  15. Electromyography: Diseased (myogenic/myopathic)
    • ⋅ No activity in muscle at rest
    • ⋅ Number of motor units firing under voluntary action unchanged
    • Motor unit potentials reduced in size : each MU has fewer surviving muscle fibres.
  16. Nerve conduction studies
    • - Record surface EMG
    • - Electrically stimulate motor nerve at 2 sites
    • - Measure latencies of muscle APs from each site (t1,t2)
    • - Distance(D) between stimulation sites
    • - Conduction velocity = D/(t2-t1)
    • CV slowed = demyelination/nerve compression.
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ms Lecture 5
2014-08-22 17:47:06

Lecture 5 of Motor systems
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