Review of Skeletal Muscle Physiology - Montemayor Flashcards
(45 cards)
40yo M perioral numbness
- ate puffer fish
- muscle weakness
- respiratory and speech involvement
- IV hydration, intubation, sedation, activated charcoal
toxin?
tetrodotoxin (TTX)
-no specific lab - diagnosis on dietary history
activated charcoal binds toxin
MOA tetrodotoxin
blocks voltage gated Na channels**
depolarization is inhibited
-AP generation and propagation is inhibited
change most rapidly hypopolarize the RMP
blockage of K leak channels
dendrotoxin
from mamba snakes
dendrotoxin MOA
blocks voltage gated K channels
inhibits repolarization phase
dendrotoxin on ACh release at NMJ
inhibits repolarization
-prolongs the action potential
ACh release requires Ca - due to AP
so have prolonged Ca influx
-increased ACh release**
hyperexcitability and convulsion
5yo M dental clinic
- general anesthesia
- halothane mask induction
- temp rises, muscle rigidity, tachycardia, elevated PCO2
- admitted to hospital
malignant hyperthermia
malignant hyperthermia
rare, heritable
- auto dom
- triggered by anesthetics and muscle relaxants
mutated ryanodine receptor
- disorder of Ca regulation
- uncontrolled release of Ca from SR
rigidity, tachycardia, hyperventilation, hyperthermia
acute hypermetabolic state - prolonged contraction of muscle
mutation in malignant hyperthermia
RYR1
ryanodine receptor
SR membrane
Ca release channel
DHPR receptor
dihydropyridine receptor
-L-type Ca channel
located T tubules
DHPR MOA
voltage sensor
-detect presence of arriving depolarization
Ca in skeletal muscle
binds troponin C
- remove tropomyosin from actin
- cross bridges form
number of cross bridges
proportional to tension created
muscle relaxation
need ATP
-to unbind actin and myosin
also to remove Ca from sarcoplasm
SERCA
sarcomplasmic and endoplasmic reticulum Ca ATPase
primary pump for removing Ca from sarcoplasm in order for relaxation of skeletal muscle to occur
most important mechanism for returning Ca to resting levels in skeletal m
SERCA pump
on SR - reuptake
27yo F enlarged thymus
- difficulty reading
- diplopia
- blurry vision
- muscle weakness
- Abs against nicotinic ACh receptor in plasma
myasthenia gravis
myasthenia gravis
get worse throughout day
and improve with rest**
extraocular muscles first affected
also bulbar, neck, prox limb muscles
Ab against nAChR
myastenia gravis
end plate potential in myasthenia gravis
absent
fewer channels able to open
-decreased ability to generate end plate potential
ACh binding nAChR in skeletal muscle at motor end plate
opening of ligand gated cation channels and depolarization of end plate to Vm between Na and K equilibrium
end plate potential
opening of nAChR channel at motor end plate
nACh receptor
permeable to cations
Na and K become equally permeable
-relative increase in Na permeability
Vm shifts to value between E-K (-80) and E-Na (+50)
