Contraction of Skeletal Muscle

Sliding filament theory of contraction

(Excitation-Contraction Coupling)

Functional Anatomy of

Skeletal Muscle

Arrival of nerve impulse (action potential)

Influx of Ca2+ into the pre-synaptic membraneAttraction of synaptic vesiclesFusion of vesicular & pre-synaptic membranesRelease of neurotransmitter (Ach) into the synaptic cleftBinding of Ach with its nicotinic receptor on post-synaptic membraneInflux of Na1+ into the post-synaptic membraneFiring of action potential on post-synaptic membrane (sarcolemma)

Propagation of action potential along Propagation of action potential along sarcolemma and deep via T-tubulessarcolemma and deep via T-tubules

Release of Ca2+ from sarcoplasmic reticulum to be near the myofilaments

What happens at the sarcomere level?

full full contractionSarcomere shortens towardSarcomere shortens toward

full full contractionSarcomere shortens towardSarcomere shortens toward

full full contractionSarcomere shortens towardSarcomere shortens toward

full full contractionSarcomere shortens towardSarcomere shortens toward

Cleavage of ATP into ADP and PCleavage of ATP into ADP and P ii

CaCa2+ 2+ binds troponin Cbinds troponin C

DetachmentDetachment of Pof Pii

Actin-myosin cross-bridgeActin-myosin cross-bridge

Tilting Tilting of myosin heads and of myosin heads and slidingsliding of actin along of actin along myosinmyosin

RelaxationRelaxation

Arrival of new Arrival of new ATPATP

The cycle is repeatedThe cycle is repeated

DetachmentDetachment of Pof Pii

SlidingSliding

SlidingSliding

RelaxationRelaxation

The cycle is repeatedThe cycle is repeated

Until full Until full contraction

The cycle is repeatedThe cycle is repeated

Until full Until full contraction

The cycle is repeatedThe cycle is repeated

Until full Until full contraction

The cycle is repeatedThe cycle is repeated

Accept Accept mymy

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