Disorders Of Motor Units Flashcards
Components of motor unit:
Alpha motor neurone
Skeletal muscle
NMJ
What are the 2 variants of the classification of motor neurones
Upper motoneurone
Lower motoneurone
Lower motoneurone signs
Loss of muscle tone
Weakness in muscle
Flaccidity
Fasciculations - twitching
Atrophy - waste away
Is re innervation always successful?
Re Innervation to original effector organ not always successful
Leads to unexpected results or syndromes
What would loss/ damage to soma result in?
Death of motoneurone
What does Polio Myelitis target
Communicable infection that targets cell bodies of LMN
Toxic infection (death) of cell bodies in ventral horn
What causes polio myelitis
Infection by polio virus
How is polio myelitis prevented
By immunisation programmes
What is the effect of polio myelitis
Death of motoneurones leads to denervation hence paralysis of muscles they innervate
What are the 2 possible targets of motoneurone disease
- UMN and LMN
- LMN only
What is programmed cell death known as
Apoptosis
2 variant examples of motoneurone disease
Lou Gherigs Disease
Amyotrophic lateral sclerosis
Which motor neurone are susceptible to motor neurone disease
Motor neurones supplying 6 extraocular muscles
Motor neurones supplying the anal sphincter (neural root values S2-24
How else can motor neurones be damaged/ death
(Rare) Infection of ventral horn of grey matter
Crashing injuries to spinal cord - damage grey matter
What is denervation
Loss of innervation for the muscle
How can complete transaction of axons of a motor nerve occur
Crushing injuries to a nerve
Stabbing injuries
Usually accidental
What is Guillain-Barre Syndrome
Acquired as a complication following a viral infection like a common cold
Clinical signs reverse when condition is cured or goes into remission
Clinical motor signs can return with a relapse
What does diabetic neuropathy demyelinate?
Both sensory and motor axons
What is botulinum toxin and how is it cultured?
Unskilled domestic preservation of cooked food can lead to culturing of botulinum toxin
Badly preserved tinned food commonest cause
Ingestion of toxin leads to paralysis of muscles
How does botulinum toxin work to cause muscle paralysis
Depletes presynaptic terminal of the NMJ of its neurotransmitter
What are nerve gases
Phosphorus containing organic chemicals (organophosphates)
Used during world wars
How do nerve gases cause damage
Act by blocking acetylcholinesterase from breaking down ACh in NMJ
What is myasthenia Gravis
Rare genetic disease of NMJ
Nicotinic receptors of post synaptic membrane on NMJ are destroyed by IMS
Affects any NMJ
Flaccid weakness of affected muscles
Can cause respiratory failure if muscle of respiration are affected
What is Duchenne Muscular Dystrophy
Genetic
Progressive muscle weakness
Defects in muscle proteins
Death of muscle tissue
Eventual death of individual
