Myasthenia Flashcards

1
Q

This toxin cleaves presynaptic proteins involved in vesicle formation and block vesicle docking with the presynaptic membrane

A

Botulinum toxin

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2
Q

This condition results from antibodies to presynaptic calcium channels

A

LAMBERT EATON Myasthenia gravis syndrome

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3
Q

In LAMBERT EATON myasthenia gravis syndrome, why are antibodies to presynaptic calcium channels bad?

A

This prevents vesicle release

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4
Q

Which calcium channels are affected in LAMBERT EATON myasthenia gravis syndrome?

A

Presynaptic

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5
Q

LAMBERT EATON Myasthenia gravis syndrome has a strong association with which type of cancer?

A

Underlying small cell carcinoma

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6
Q

Name 2 PRE-synaptic disorders

A
  • botulism

- lambert eaton myasthenia gravis syndrome

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7
Q

Name a POST-synaptic disorder

A

Myasthenia gravis

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8
Q

Most common disorder of neuromuscular junction

A

Myasthenia gravis

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9
Q

In myasthenia gravis, the antibodies are targeted against which receptors?

A

Acetyl choline receptors (AChR)

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10
Q

Reduced numbers of functioning receptors leads to what _____

A

Muscle weakness and fatiguability

myasthenia gravis

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11
Q

In myasthenia gravis, symptoms start when ACh receptors reduced to __% of normal

A

30% of normal

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12
Q

Flattening of endplate folds?

A

Myasthenia gravis

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13
Q

Apart from blocking the binding of ACh, what do the antibodies in myasthenia gravis do?

A

Trigger inflammatory cascades that damage the folds of the postsynaptic membrane

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14
Q

Which other gland-y thing plays a role in myasthenia gravis?

A

The thymus - 75% of patients have hyperplasia or thymoma

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15
Q

When are the two peaks of incidence in myasthenia gravis?

A

Females in the third decade
Males in 6th/7th decade
(female:male ratio - 3:2)

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16
Q

What is the most common presentation of myasthenia gravis?

A

Extraoccular weakness, facial and bulbar weakness

17
Q

If limbs become weak in myasthenia gravis, are distal or proximal usually affected?

A

Proximal

18
Q

Treatment for myasthenia gravis?

A

Pyridostigmine (acetylcholinesterase inhibitor)
Thymemctomy

Steroids/aziathioprine (immune modulating)
Emergency treatment - plasma exchange/immunoglobulin

19
Q

Emergency treatment for myasthenia gravis?

A

Plasma exchange or immunoglobulin

20
Q

What is the motor endplate?

A

The synapse between the motor neuron and the muscle

21
Q

IV drug users are at risk of this presynaptic disorder

A

Botulism (can get it from black tar heroin)

22
Q

Treatment for myasthenia gravis

A

Acetylcholinesterase inhibitor - pyridostigmine

Thymemctomy

23
Q

How does pyridostigmine work?

A

Stops acetylcholinesterase working

24
Q

Smallest contractile unit of skeletal muscle

A

The muscle fibre

25
Q

Type I muscle fibres

A

Slow oxidative

  • dense capillary network
  • myoglobin
  • resist fatigue
26
Q

Type IIa muscle fibres

A

Fast oxidative

-aerobic metabolism

27
Q

Type IIb muscle fibres

A

Fast glycolytic

-easily fatigued

28
Q

What is myotonia?

A

When the muscle cannot relax after use

-chloride channel

29
Q

Why should you be particularly concerned with dermatomyositis?

A

up to 50% have underlying malignancy

30
Q

This disease presents with slowly progressive weakness in the 6th decade of life with CHARACTERISTIC THUMB SPARING

A

Inclusion body myositis

31
Q

Rhabdomyolysis triad

A

Myalgia
Weakness
Myoglobinuria

32
Q

NEED 2 KNOW: epidemiology of myasthenia gravis

A

2 incidences: women in the 3rd decade, men in the 6th/7th decade
F:M 3:2

33
Q

How does a neuromuscular junction work?

A

Action potential travels along nerve
Voltage gated calcium channels open allowing lots of calcium in!!
Vesicles of acetylcholine released into synaptic cleft
Acetylcholine binds to receptors and this opens the Na/K channels
Depolarisation starts an action potential at the motor endplate

34
Q

Name 2 possible causes of rhabdomyolysis

A
  • DIC

- renal failure