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How do muscles move the skeleton?
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Antagonistic pairs
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The neuromuscular junction
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Summary – controlling movement
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The structure of skeletal muscle
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The structure of the sarcomere
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Understanding the sarcomere’s bands
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The sarcomere – structure to function
Hansen and Huxley realized that the interlocking structure of
the thick and thin filaments allows them to slide past one
another. This reduces the length of the sarcomere.
contraction
At the same time the banding pattern of the sarcomere
changes; light bands, formed by actin, shrink as the filaments
become more interlocked.
In 1954 Hansen and Huxley published their work explaining
muscle contraction using their sliding filament theory.
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The sliding filament theory
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How does the sarcomere change?
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The structure of actin
The actin filament is formed from a helix of actin sub-units.
Each contains a binding site for the myosin heads.
troponin
tropomyosin
actin sub-unit
myosin head
binding site
Two other proteins are attached to the actin fibre:

tropomyosin is wound around the actin

troponin molecules are bound to tropomyosin
and contain calcium ion binding sites.
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What controls the sliding filaments?
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Summary – muscle contraction
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Glossary
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Sarcomere structure
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What’s the keyword?
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Multiple-choice quiz
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