Neuromuscular Junction

Question 1

what is the motor end plate

Answer 1

synapses between motor neurons and muscles

Question 2

what neurotransmitter is released from motor neurones

Answer 2

acetyl choline

Question 3

what triggers release of acetyl choline from motor neurones

Answer 3

opening of voltage gated calcium channels (Ca influx)

Question 4

effect of acetyl choline on muscle cells

Answer 4

makes the membrane permeable to Na/K ions starting action potential

Question 5

effect of acetylcholinesterase

Answer 5

breaks down acetyl choline to acetate and choline

Question 6

what is lambert eaton myasthenic syndrome

Answer 6

antibodies to presynaptic calcium channels

means less acetyl choline vesicle production and release

Question 7

what condition is lambert eaton myasthenic syndrome strongly associated with

Answer 7

small cell carcinoma

Question 8

what is the most common disorder of the neuromuscular junction

Answer 8

myasthenia gravis

Question 9

what is myasthenia gravis

Answer 9

autoimmune antibodies to post-synaptic acetyl choline receptors
reduced numberof functioning receptors leading to muscle weakness and fatigue

Question 10

Transmission improves with increased amount of acetyl choline in myasthenia gravis. True/false

Answer 10

False

even with normal amounts of Ach, transmission becomes ineffective

Question 11

what organ plays a role in myasthenia gravis

Answer 11

thymus - 75% patients have hyperplasia or thymoma

Question 12

clinical features of myasthenia gravis

Answer 12

fluctuating weakness - worse through the day

proximal limb weakness

Question 13

most common presentation of mysasthenia gravis

Answer 13

extraocular, facial and bulbar weakness

Question 14

treatment for myasthenia gravis

Answer 14

acetylcholinesterase inhibitor - pyridstigmine
thymectomy
immunomodulating
steroids/azathioprine

Question 15

common causes of morbidity in myasthenia gravis

Answer 15

respiratory failure

aspiration pneumonia side effects from immunosuppression

Question 16

what are clinical features of skeletal muscle disorders

Answer 16

proximal weakness - shoulder and hips
cant lift things/get out of chair
waddling gait - gower’s sign
LMN signs - weakness, wasting, hypoflexia, fasiculations

Question 17

what trigger fasiculations

Answer 17

stress
caffeine
fatigue

Question 18

what is myotonia

Answer 18

failure of muscle relaxation after use

Question 19

causes of muscle problems

Answer 19

inflammatory - dermatomyositis
polymyositis
inherited - muscular dystrophies
congenital

Question 20

polymyositis presentation

Answer 20

symmetrical progressive proximal weakness

Question 21

what is raised in polymyositis

Answer 21

CK

Question 22

what additional clinical feature is present in dermatomyositis

Answer 22

skin lesions

heliotrope rash on face

Question 23

treatment for polymyositis/dermatomyositis

Answer 23

steroids

Question 24

what is the most common muscular dystrophy

Answer 24

myotonic dystrophy

Question 25

mode of inheritance of myotonic dystrophy

Answer 25

autosomal dominant - trinucleotide repeat disorder with anticipation

Question 26

clinical features of myotonic dystrophy

Answer 26

``` myotonia weakness cataracts ptosis frontal balding cardiac defects ```

Question 27

what conditions are mitochondrial disease associated with

Answer 27

deafness diabetes epilepsy

Question 28

what drugs can cause muscular dystrophies

Answer 28

statins anaesthetic agents cocaine GHB venoms

Question 29

how does rhabdomyolysis cause muscular dystrophy

Answer 29

dissolution of muscle | leakage of toxic intracellular contents into plasma

Question 30

clinical features of rhabdomyolysis

Answer 30

triad of: myalgia weakness myoglobinuria (dark urine)