Physiology Flashcards
What defines a sarcomere?
Z-line to Z-line
What makes up thick filament?
myosin
What are invaginations of sarcolemma called?
t-tubules
What surrounds t-tubules?
sarcoplasmic reticulum
What is held in sarcoplasmic reticulum?
Ca
What makes up the triad in a skeletal muscle cell?
t-tubule sarcoplasmic reticulum (x2)
What makes up the thin filament?
actin, tropomyosin, troponin
What is the function of troponin?
bind Ca and pull tropomyosin away from actin
What is a motor unit?
a single motor neuron and the fibers that it innervates
Where are the ACh receptors found at the NMJ?
top of the folds
Where are V-gated Na channels at the NMJ?
bottom of folds and longitudinal surfaces
Where are V-gated L-type Ca channels?
t-tubules
How are ryanodine receptors activated?
coupled to L-type Ca channels
What is the function of ryanodine receptors?
allow Ca from the SR into the cytosol
How many action potentials are needed to bind all troponin to Ca?
1
Describe cross bridge cycling
- ATP binds to myosin and causes release from actin
- ATP loses a phosphate and the myosin head returns to vertical
- Myosin-ADP reattaches to actin
- power stroke adn ADP diffuses off
What causes myosin to detach from actin?
ATP
How is Ca taken back into the SR?
SERCA pumps (ATPase)
What is a twitch?
quick contraction from a single AP
What is tetanus?
sustained contraction from repeated APs
How are APs summated?
New AP fires before all the Ca is cleared from the cytosol
Hallmarks of Type 1 muscle fibers
oxidative phosphorylation
contains myoglobin but not glycogen
slow twitch
does not fatigue
Hallmarks of Type 2B fibers
glycolytic
fast twitch
white (no myoglobin)
fatigues quickly
Hallmarks of Type 2A fibers
fast oxidative
has myoglobin and glycogen
medium fatigue resistance
What is at the center of the sarcomere?
M line
What band/zone surrounds the M line?
H zone
What band/zone includes the entire thick filament?
A band
What band/zone surrounds the Z disk?
I band
What bands/zones shorten with contraction?
I band
H zone
