Electrophysiology Flashcards
myasthenia gravis
antibodies against nAChR
decreased, but not absent EPP
affects extraoccular region
ice pack test helps
-decreased acetylcholinesterase activity
lambert eaton myasthenic syndrome (LEMS)
association with lung cell carcinoma
LEMS is pre or post synaptic?
presynaptic
because it has antibodies against voltage gated calcium channels
no fusion of vesicles
enough calcium release eventually happens to cause AP
-strong contraction
botulin?
inhibits ACh vesicle fusion
hyperkalemic periodic paralysis
after exercise
and after ingesting potassium
muscle spasms and myotonia
autosomal dominant on chromosome 17 SCN4A
- problem is voltage gated sodium channels
- inactivation gate
what does hyperkalemia do to RMP?
becomes more positive
-bc of potassium leak channels
RMP closer to the threshold
what happens if you can’t inactivate the sodium channels
continuous influx of sodium
continue to depolarize
keep it in a hyperexcitable state
what can hyperkalemia do?
can depolarize and cause inactivation gate on sodium channels
**constant absolute refractory period
mild depolarization 5-10
myotonia, hyperexcitability
greater depolarization 20-30
weakness or paralysis
why would carbohydrate help with depolarization problem?
sodium potassium pump
can help to fix the polarization problem
malignant hyperthermia
rare autosomal dominant disorder
affects the release of calcium from SR
-defective RyR
DHP receptors?
T tubule membrane
RyR receptors
SR membrane
why do cold temperatures help symptoms of MS?
slow voltage gated sodium channels
lengthen AP duration
