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Epimysium
dense irregular CT surrounds entire muscles
Perimysium
dense irregular CT surrounds groups of fascicles
endomysium
Areolar CT surrounds each muscle fiber
sacroplasm
cytoplasm of skeletal muscle cell
excitability
generates action potential
contractibility
ability to contract; result of action potential
extensibility
ability to extend/ lengthen
elasticity
ability to stretch and go back to original size
sacrolemma
plasma membrane of skeletal muscle cell
Transverse (T-Tubule)
Plasma membrane going inside the cell
sarcoplasmic reticulum
endoplasmic reticulum of skeletal muscle cell
stores and releases calcium
Terminal cisternae
Enlargement of sarcoplasmic reticulum on the sides of the T-Tubules
triad
2 terminal cisternae + T-Tubule
Myofibrils
Composed of myofilaments
thick filaments
Mysosin
Contractile protein
Myosin heads binds with actin active site

thin filament
Actin protein
Contractile protein
Tropomyosin protein
Troponin protein

Tropomyosin
covers actin active sites: prohibits binding to myosin head
troponin
locks tropomyosin in place
Z disc
anchors thin filaments
“Endline”
Middle of the I band
I band
Thin filaments ONLY
Light appearance
A band
Overlap of thin and thick filaments
Dark appearance
H zone
Middle of A Band
Thick filaments
M line
“Midline”
Bisects H Zone
Anchors thick filaments
Synaptic cleft
space between axon terminal and motor end plate
motor end plate
folds of plasma membrane
depolarization
If end plate potential reaches threshold (-65 mV)
Voltage gated NA/K channels open
Na+ channels open quicker than K+
Na+ flow in triggers depolarization; jumps to 30 mV
AP spreads across sacrolemma
repolarization
Voltage gated Na+ channels close
Voltage gated K+ channels fully open
K+ flowing out restores RMP
RMP maintained by….
NA/K pump
Leaky NA and K channels
crossbridge formation
Myosin head binds to active active site
power stroke
Release of ADP + Pi from myosin head
Myosin pulls actin towards M line
crossbridge detachment
add ATP to myosin head to detach