Muscle and NMJ

Question 1

What are hte features of lower motor neurone disorders?

Answer 1

weak; low tone and fasciculations

Question 2

What is the motor end plate?

Answer 2

the synapse formed between motor neurons and muscle

Question 3

How does botulinum toxin affect the presynaptic cleft?

Answer 3

cleaves presynpatic proteins involved in vesicle formation and block vesicle docking with the presynpatic memrbane

Question 4

What happens in lambert-eaton myasthenic syndrome/

Answer 4

antibodies to presynaptic calcium channels leads to less vesicle release

Question 5

What is lambert-eaton syndrome associated with?

Answer 5

small cell carcinoma

Question 6

What happens in myasthenia gravis?

Answer 6

antibodies to acetyl choline receptors reducing number of receptors and triggering an inflammatory cascade flattening of endplate folds

Question 7

What is other organ is found to be involved with myasthenia gravis?

Answer 7

thymus- 85% have hyperplasia or thymoma

Question 8

When are the 2 peaks of incidence for myasthenia gravis?

Answer 8

females in the 3rd decade and males in 6th or 7th decade

Question 9

What are the lcinical features of myasthenia gravis?

Answer 9

wekaness getting worse over the day; proximal limb weakness; commonly extraocular weakness; facial and bulbar weakness

Question 10

What is the acute treatment for myasthenia graivs?

Answer 10

acetylcholinesterase inhibitor- pyridostigmine; IV immunoglobulins

Question 11

What is the chronic treatment fro myasthenia gravis?

Answer 11

thymectomy; steroids/ azathioprine

Question 12

What are the common causes of morbidity in myasthenia gravis?

Answer 12

resp failure and aspiration pneumonia; porblems with immunosuppression and steroids in the elderly

Question 13

What connective tissue are individual muscles surrounded by?

Answer 13

epimysium

Question 14

What is a sarcomere?

Answer 14

from one Z line to another- smallest contractile unit of muscle

Question 15

What are fasciculations?

Answer 15

visible, fast, fine, spontaneous twitches

Question 16

When do fasciculations occur pathologically?

Answer 16

in denervated msucle which has become hyperexcitable- usually problem in motor neurone not muscle

Question 17

What is mytonia?

Answer 17

failure of muscle relaxaion after use due a problem with chloride channels

Question 18

What are the features of polymyositis?

Answer 18

symmetrical, progressive proximal weakness developing over weeks to months with raised CK

Question 19

What are the features of inclusion body myositis?

Answer 19

similar to sarcopenia but arises earlier than normal but has chracteristic thumb sparing

Question 20

What is the inheritance of myotonic dystrophy?

Answer 20

autosomal dominant

Question 21

What are the features of myotonic dystrophy?

Answer 21

myotonia; weakness; cataracts; ptosis; frontal blading; cardiac defects

Question 22

What happens in rhabdomyloysis?

Answer 22

damage to SK muscle causes leakage of large quantities of toxic intracellular contents into plasma

Question 23

What are the features of rhabdomylosis?

Answer 23

myalgia; msucle weakness and myoglobinuria

Question 24

What are the complications of rhabdomyolysis?

Answer 24

acute renal failure and DIC