Disorders Of Motor Units

Question 1

Components of motor unit:

Answer 1

Alpha motor neurone
Skeletal muscle
NMJ

Question 2

What are the 2 variants of the classification of motor neurones

Answer 2

Upper motoneurone
Lower motoneurone

Question 3

Lower motoneurone signs

Answer 3

Loss of muscle tone
Weakness in muscle
Flaccidity
Fasciculations - twitching
Atrophy - waste away

Question 4

Is re innervation always successful?

Answer 4

Re Innervation to original effector organ not always successful
Leads to unexpected results or syndromes

Question 5

What would loss/ damage to soma result in?

Answer 5

Death of motoneurone

Question 6

What does Polio Myelitis target

Answer 6

Communicable infection that targets cell bodies of LMN
Toxic infection (death) of cell bodies in ventral horn

Question 7

What causes polio myelitis

Answer 7

Infection by polio virus

Question 8

How is polio myelitis prevented

Answer 8

By immunisation programmes

Question 9

What is the effect of polio myelitis

Answer 9

Death of motoneurones leads to denervation hence paralysis of muscles they innervate

Question 10

What are the 2 possible targets of motoneurone disease

Answer 10

1. UMN and LMN
2. LMN only

Question 11

What is programmed cell death known as

Answer 11

Apoptosis

Question 12

2 variant examples of motoneurone disease

Answer 12

Lou Gherigs Disease
Amyotrophic lateral sclerosis

Question 13

Which motor neurone are susceptible to motor neurone disease

Answer 13

Motor neurones supplying 6 extraocular muscles
Motor neurones supplying the anal sphincter (neural root values S2-24

Question 14

How else can motor neurones be damaged/ death

Answer 14

(Rare) Infection of ventral horn of grey matter
Crashing injuries to spinal cord - damage grey matter

Question 15

What is denervation

Answer 15

Loss of innervation for the muscle

Question 16

How can complete transaction of axons of a motor nerve occur

Answer 16

Crushing injuries to a nerve
Stabbing injuries

Usually accidental

Question 17

What is Guillain-Barre Syndrome

Answer 17

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

Question 18

What does diabetic neuropathy demyelinate?

Answer 18

Both sensory and motor axons

Question 19

What is botulinum toxin and how is it cultured?

Answer 19

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

Question 20

How does botulinum toxin work to cause muscle paralysis

Answer 20

Depletes presynaptic terminal of the NMJ of its neurotransmitter

Question 21

What are nerve gases

Answer 21

Phosphorus containing organic chemicals (organophosphates)
Used during world wars

Question 22

How do nerve gases cause damage

Answer 22

Act by blocking acetylcholinesterase from breaking down ACh in NMJ

Question 23

What is myasthenia Gravis

Answer 23

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

Question 24

What is Duchenne Muscular Dystrophy

Answer 24

Genetic
Progressive muscle weakness
Defects in muscle proteins
Death of muscle tissue
Eventual death of individual