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myofibrils

inside muscle fiber, same length fiber encircled by T tubules composed of myofilment

filaments 2 type of

thin filament-protein actin, thick filaments protein myosin

filaments

responsible for muscle contraction/ anchored in inner surface of sarcolemma outer surface of sarcolemma attached to collagen fibers of tendon

sarcoplasmic reticulum (SR)

similar to smooth ER of other cells, tubular network , surr each myofibril

SR

form terminal cisternae at either side of T tubule/ 2 terminal cisternat + 1 T tubule = Triad

terminal cisternae

Ca++ actively transported from sarcoplasm

Ca++

relased into sarcoplasm contraction begins

sarcomeres

smallest function unit , capable of contraction

I band in sarcomeres

light-actin only thin filament extend to A band

Z lines

boundary between sarcomeres, interconnect thin filaments in sarcomere

titn-elastic protein

forms core to thick filaments @ Z line functions to restoration of fiber length after contraction

A bands

dark myosin 3 subdivisons

3 subdivions of A bands

M line, H band zone of overlap

M line

center of each thick filament interconnected by proteins

H band

either side of M line-only thick filament

zone of Overlap

thin filaments between thick filaments, darkest

muscle contraction

Ca+ expos to active sites, formation of cross-bridges, pivoting of myosin heads, etachment of cross-bridges, reactivation of myosin

sliding filament theory

thin filaments slide alongside thick filaments then muscle fiber shorters

excitation contraction coupling

start of action potential int the sarcolemma snd the start of a muscle contraction called

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