chapter 6 Flashcards
skeletal muscle characteristics
voluntary, striated, multinucleated, long cells
a band
thick + thin filaments, run entire length of sarcomere, dark band
i band
thin filaments in sarcomere, light band
m line
where myosin filaments are anchored, center of a band
h zone
ONLY thick filaments. shortens/disappears in contraction
z line
where thin filaments attach and sarcomere ends
thick band
myosin
thin band
actin, troponin, + tropomyosin
sarcolemma
the cell membrane of muscle fiber
transverse tubules (t-tubules)
modifications of the sarcolemma that entend into cell interior wall + surround myofibrils. carry electricity
sarcoplasmic reticulum
specialized ER that forms tubular network around myofibrils
cisternae/cisterns
chambers of sarcoplasmic reticulum that store calcium
sarcomere
functional unit of muscle contraction
myomesin
makes up m line which anchors myosin filaments
alpha-actinin
makes up z line which anchors myosin + actin filaments
what do myosin filaments bind?
ATP + actin in cross bridge formation
what is the mechanism of sarcomere contraction called?
rachet mechanism
troponin
3 globular protein that binds to Ca2+ to regulate cross bridge formation
troponin T
attaches troponin to tropomyosin
troponin I
inhibits the interaction of actin binding to myosin
troponin C
binds Ca2+ to permit the interactions of actin and myosin
what happens if there is no calcium for the sarcomere to use?
no contraction occurs
step 1 of skeletal muscle contraction mechanism
sarcolemma stimulated which generates an action potential
step 2 of skeletal muscle contraction mechanism
AP travels to myofibrils via t-tubules
step 3 of skeletal muscle contraction mechanism
AP triggers release of calcium ions from SR
step 4 of skeletal muscle contraction mechanism
calcium binds to troponin causing tropomyosin to move, uncovering the binding sites on actin for myosin
step 5 of skeletal muscle contraction mechanism
myosin binds to actin causing actin to slide past myosin, toward the m-line. results in contraction of sarcomeres
cross bridge cycle step 1
rigor state - no ATP bound