ms Lecture 5
Card Set Information
ms Lecture 5
Lecture 5 of Motor systems
How do you call diseases of
a) Nervous tissue
b) myasthenia gravis/syndrome
Motor unit functional components
⋅MN cell body
General features of neurogenic and myopathic diseases (see on notes sheet)
No answer given
Fasciculation VS Fibrillation
Fasciculation = small visible muscle twitches (
Fibrillation = small spontaneous twitches of
single muscle fibres
, not visible, require EMG analysis.
A patient has distal limb weakness and fibriallations. Neurogenic or myopathic?
Neurogenic : Myopathic would include proximal limb weakness.
LOWER MOTONEURONES (LMNs) + Lesion effects
⋅Innervated skeletal muscle directly
⋅Located in spinal cord ventral horn/ cranial nerve nuclei
: weakness, atrophy, ↓ tendon reflexes, ↓ tone, fasciculation
UPPER MOTONEURONES (UMNs) + Lesion effects
⋅Originate in higher motor centre (eg. celebral cortex)
⋅Synapse with LMN
⋅Relay descending commands
: Weakness, (no paralysis, no/little citrophy), ↑ tendon reflexes, ↑ tone (spasticity), Babinski (extensor plantor responses)
What does the presence of both LMN and UMN lesion signs indicate?
Amyotrophic lateral sclerosis (LGU Gehrig disease; motor neurone disease)
Tests to distinguish Neurogenic & myogenic diseases
⋅Nerve conduction studies
DIAGNOSTIC SERUM ENZYME MEASUREMENT
⋅ 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
Examples of enzymes that can be detected via serum enzyme measurement
- Creatine kinase (CK)
- Serum glutamic-oxaloacetic transaminase (SGOT)
- Lactate dehydrogenase (LDH)
Electromyography (in diagnosis of neurogenic/myopatic disease)
Action potentials of
groups of neighboring
motor units using
-spontaneous activity at rest
-number of MUs under voluntary control
-duration & amplitude of motor unit APs
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.
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.
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.
Nerve conduction studies
- Record surface
stimulate motor nerve
of muscle APs from each site (t
between stimulation sites
CV slowed = demyelination/nerve compression.