BRAINCAKESliding Filament Model
The muscle contracts when the actin and myosin filaments slide past each other. The myosin heads attach to the actin filaments and pull them towards the centre of the sarcomere. The H-zone and light band become narrower as the Z-lines move closer together. Lots of sarcomeres contract together to enable enough force to pull on bones and cause movement. The muscle relaxes as the sarcomeres return to their original position.
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Key terms in this lesson
- sarcomere
- The contractile unit of a myofibril, delineated by two Z-lines, containing overlapping actin and myosin filaments.
- actin
- A thin protein myofilament in a myofibril that, together with myosin, slides during muscle contraction; its myosin-binding sites are covered by tropomyosin in resting muscle.
- myosin
- A thick protein myofilament with a hinged globular head that binds to actin and ATP and pulls actin filaments during muscle contraction.