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MUSCLE PHYSIOLOGY

Skeletal Mustlc: Excitation-Contracti»n Coupling I

Thin

Electric impulse Sarcolemma

Sarcoplasm

/ band    Sarcoplasmic

reticulum

Terminalcistern of sarcoplasmic

Terminal cistom ot sarcoplasmic reticulum

Electric impulse traveling atong muscle celi membrano (sarcolemma) from motor cndplate    r

(neuromuscular junctionl and then along transverse tubules aftects sarcoplasmic reticulum, causing extrusion of Ca² to imtiato contraction by "rowing action of cross bridges, sliding Ą filanients past one another

Figurę 3.3 Excitation-Coniraction Coupling_

Impulsos from motor neurons release acetylcJH>line (ACh) at the neu romuscular junction. The ACh receptor on the plasma membrano of the muscle llber is a cation rhannel that opens whon it binds ACh. As extracellular Na* enters the celi through the cation channol, the membrano depolarizes and an action potential is gonerated. The action potential sproads across the frber and travcls down specialized mvage nations called transverse (T) tubules. fhe I tubules are m dtxt xa tion to the terminal cistemae of the sarcoplasmic retnulum S*.. the spreading wave ot depolari/ation along the T tubułe casc i release from the SR. C)ther regions ot the SR also contam Car' A which serves to rapidly reaccumulate the released Ca-' ane contraction.

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