Muscle Problems

Question 1

Where do motor neurons cell bodies arise from?

Answer 1

ventral horn of the spinal cord

Question 2

What is the motor end plate?

Answer 2

the synapse between the muscle and the motor neurones

Question 3

How many motor neurones does each muscle cell respond to?

Answer 3

ONE MOTOR NEURONE = ONE MUSCLE CELL

Question 4

What is Curare?

Answer 4

a toxin that acts in the same position as Ach but does not open the channel

Question 5

What does Curare lead to?

Answer 5

no muscle contraction = no respiration

Question 6

Name 2 pre synaptic disorders?

Answer 6

Botulism

Lambert Eaton Myasthenic syndrome

Question 7

What is Botulism?

Answer 7

rapid onset weakness WITHOUT SENSORY LOSS

Question 8

What causes Botulism?

Answer 8

clostridium botulism - heroin is often contaminated with it, or it is found in soil

Question 9

What is the action of botulism toxin to cause the problems?

Answer 9

cleaves pre synaptic proteins involved in vesicle formation and blocks vesicle docking with the presynaptic membrane

Question 10

What is the presentation of Lambert Eaton syndrome?

Answer 10

very like Myasthenia gravis
weakness throughout the day
extraocular and facial weakness

Question 11

What causes LES?

Answer 11

antibodies to presynaptic calcium channels leads to less vesicle release
strong association with underlying small cell carcinoma

Question 12

What is the treatment for LES?

Answer 12

3-4diaminopyridine

Question 13

What type of disorder is myasthenia gravis?

Answer 13

post synaptic disorder

Question 14

What is the pathophysiology behind myasthenia gravis?

Answer 14

autoimmune disorder - antibodies to acetyl choline receptors

reduced number of receptors leads to muscle weakness and fatigue

Question 15

What is the pathophysiology of myasthenia gravis?

Answer 15

reduced number of ACh receptros and flattening of end plate folds leads to inefficeint transmission of ACh

Question 16

What is the epidemiology of myasthenia gravis?

Answer 16

females in 30s
males in 60-70s
females>males

Question 17

What is the presentation of myasthenia gravis?

Answer 17

symptoms start when ACh receptros are reduced to 30% of normal
Ach antibodies are found in 80-90% of patients
weakness is typically worse throughout the day
extraocular weakness and facial and bulbar weakness
proximal limb weakness
75% of patients have thymus hyperplasia or thymoma

Question 18

What is the acute treatment of myasthenia gravis?

Answer 18

aceytlcholinerase inhibitor - pyridostigmine
IV immunoglobulin - mops up antibodies
thymectomy - even in absence of thymus abnormality

Question 19

What is the chronic treatment of myasthenia gravis?

Answer 19

immunomodulation

steroids and steroid sparing agents - azathioprine or mycophenolate

Question 20

What must be avoided in myasthenia gravis and why?

Answer 20

gentamicin - precipitates it

Question 21

What is the prognosis for those with myasthenia gravis?

Answer 21

mortality 3-4%, usually from respiratory failure or aspiration pneumonia

Question 22

What are fasiculations?

Answer 22

visible, fast, spontaneous twitch in smooth muscle
normal in large muscles
abnormal in small muscles
indicates a deinnervated muscle has become overexcitable due to motor neurone disease

Question 23

What is myotonia?

Answer 23

failure of muscle relaxation after use

due to chloride channel abnormalities

Question 24

What is the presentation of myotonic dystrophy?

Answer 24

myotonia
weakness
cataracts
cardiac weakness/defects
proximal weakness
frontal balding

Question 25

What causes myotonic dystrophy?

Answer 25

autosomal dominant - trinucleotide repeat disorder

Question 26

What is rhabdomyolysis?

Answer 26

damage to the skeletal muscle that causes leakage of large quantise of toxic intracellular components into plasma

Question 27

What is the presentation of rhabdomyolysis?

Answer 27

myalgia
weakness
myoglobinuria

Question 28

What can cause rhabdomyolysis?

Answer 28

post convulsion
extreme excercise
crash injuries