Muscle diseases Flashcards
Muscle physiology recap
All or none
Release of ACh from motor nerve impulse - get depolarization if there’s enough
Ca into SR
Ca conformational change - change in tropomyosin, uncovers myosin binding head
Myosin ATPase activity
Binds actin, ratchets and releases
Fasciculations
whole motor unit twiches
easily visible
irritable nerve
Fibrillations
one muscle fiber twitches
not visible
“irritable” muscle fiber
Power scale of muscle
MRC scale 0 - nothing 1 - flicker 2 - less than gravity 3 - can oppose gravity 4 - mor ethan gravity but not complete strength 5 - complete strength, normal
Tetanus
neurotoxin from C. tetani
gets to peripheral nerve terminals and crosses synaptic junction
Binds spinal inhibitory NT, producing continuous muscle contractions
Amyotrophic lateral sclerosis
Idiopathic death of motor neurons
ALl muscles attached to motor neurons atrophy
dying nerve fibers and irritable myofibrils
fasciculation/fibrillation
Dyscalcemic state
changes in Ca concentrations, changes nerve excitability
Hypercalcemia
parathyroid tumour
excess PTH
fatigue, generalized weakness
Hypocalcemia
PTH deficiency
twitchy,tetanus, seizures
Neuromuscular junction blockage
e.g. botulism, myasthenia gravis
intermittent weakness
worse with exercise
Myasthenia gravis
autoimmune blockade of NMJ
fluctuating weakness
McArdle’s disease
glycogen storage type V
Lack of myophosphorylase - important for conversion of glycogen to G1P
exercise intolerance
inability to use glycogen
Muscle fiber damage
physical/immune injury due to trauma, polymiositis, etc
painful, stiff, cramping
Polymiositis
autoimmune-mediated muscle fiber damage found esp in proximal muscle groups - shoulders, hip girdles No fasciculations fibrillations do occur elevated CPK with muscle damage
Disuse atrophy
no fasciculations
normal CPK
not tender
