Tropomyosin is one of the protein molecules that (together with myosin, actin, and troponin) forms the cylindrical structures called myofibrils that, together, form muscle fibres.

Myofibrils consist of two types of protein filaments, called thin filaments and thick filaments. Tropomyosin molecules, together with troponin and actin molecules, form the thin filaments which have a helix structure - as shown in the diagram below.

Above: Diagram of tropomyosin molecules within a thin filament

The key function of tropomyosin is to inhibit muscle contraction by blocking the interaction of actin and myosin (which is part of the thick filaments), except when influenced by troponin.

Muscle contraction generally is regulated by the combined actions of troponin and tropomyosin, which in turn, are controlled by the concentration of calcium ions in the muscle sarcoplasm.

See more about the types of muscle contraction.

This section consists of short summaries about the structures that form the muscles of the body. This list is not exhaustive but is intended to be appropriate for students of A-Level Human Biology, ITEC courses in massage and related subjects, and other courses in health sciences. For more general information about muscles see the pages about:

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