Sarcomeres
Sarcomeres
Sarcomeres (/sɑːrˈkoʊmiːrz/; from the Greek sarx meaning "flesh" and meros meaning "part") are the basic unit of a muscle's myofibril. Sarcomeres are responsible for the striated pattern seen in striated muscle tissue.
Structure
Sarcomeres are composed of long, fibrous proteins that slide past each other when the muscles contract and relax. Two of the important proteins are actin and myosin, which form thin and thick filaments, respectively. The region of the sarcomere containing the thick filaments is the A band, while the region containing the thin filaments is the I band. The Z line marks the boundary between adjacent sarcomeres.
Function
The primary function of the sarcomere is muscle contraction. The sliding filament theory describes how the thick and thin filaments within the sarcomere slide past one another, shortening the entire length of the sarcomere and thus shortening the muscle and creating force.
Related Terms
- Myofibril: The basic rod-like unit of a muscle cell. Myofibrils are composed of long proteins including actin, myosin, and titin, and other proteins that hold them together.
- Actin: A protein that forms the thin filament in a sarcomere; responsible for muscle contraction in combination with myosin.
- Myosin: A protein that forms the thick filament in a sarcomere; works in conjunction with actin to enable muscle contraction.
- A band: The region of the sarcomere that holds the entire length of the thick filament (myosin).
- I band: The region of the sarcomere that holds the thin filament (actin) only.
- Z line: The line formed by the attachment of actin filaments between two sarcomeres, marking the boundary between each sarcomere.
External links
- Medical encyclopedia article on Sarcomeres
- Wikipedia's article - Sarcomeres
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