Muscle Physiology Flashcards
withn myofibers are what?
myofibrils
myofibrils contain what?
myofilaments
myofilaments contain what?
thick and thin filaments
what is the smallest contractile unit of skeletal muscle?
sarcomere
what is the invagination of the sarcolemma called?
T tubules
what are the three things in thin filaments?
actin, tropomyosin
troponin
when Ca binds troponin what happens to thin filaments?
it removes the tropomyosin that is guarding the thick filament binding site on the thin filament
what type of receptor is present at the peaks in the Neuromuscular junction?
nicotinic acetylcholine receptor channels
in a muscle AP, what are the important voltage gated channels called?
Calcium channels named L type or DHP receptors
what are L type voltage gated calcium channels linked to in skeletal muscle?
ryanodine receptors
what do ryanodine receptors release? from where?
release calcium from the sarcoplasmic reticulum
when myosin is fused to actin what must bind to release it??
ATP
after ATP binds myosin what happens?
releases from actin and ATP can be hydrolyzed
once ATP is hydrolyzed into ADP and P what happens?
myosin head moves forward out of cocked position
once myosin in uncocked position what happens?
will bind the actin again
once myosin is bound to actin in uncocked position what happens?
ADP releases and myosin cocks back moving the filaments
what is the H zone in sarcomere?
only thick filaments
what is the A band in sarcomere?
length of the whole thick filament, including overlap with thin
what is the I band in sarcomere?
only thin filament
what three zones shorten in a sarcomere with contractions?
HIZ
explain how tetanus occurs
muscle stimulated repeatedly so insufficient time for Ca to go back into the SR and you get sustained contraction
what are the three skeletal muscle fiber types
type 1
type2A
type2B
what color does type 1 muscle fiber appear?
red
what color does type 2A muscle fiber appear?
grey
what color does type 2B muscle fiber appear?
white
why does type 1 muscle fiber appear red?
presence of myoglobin
what does type 1 muscle fiber use for energy?
oxidative phosphorylation
what are type 1 muscle fibers good for?
sustained contraction
what muscle fiber type has lots of mitochondria?
type 1
what do type 2B muscle fibers use for energy?
lots of glycolysis…anaerobic glycolysis
are type 2B fast or slow twitch muscle fibers?
fast twitch
what movements are type 2B fibers good for?
explosive movement
why do type 2B muscle fibers appear white?
because they lack myoglobin
what is type 2A muscle fiber?
a mix between type 1 and 2B
what does type 2A muscle fiber use for energy?
glycogen and myoglobin for oxidative phosphorylation
type 2A muscle fibers are more slow or fast twitch muscles
fast
what are type 2A muscle fibers better at avoiding compared to type 2B fibers?
fatigue
can fibers change type with exercise?
yes
