Definitions for sarcomereˈsɑr kəˌmɪər
This page provides all possible meanings and translations of the word sarcomere
Random House Webster's College Dictionary
any of the segments of myofibril in striated muscle fibers.
Category: Histology, Laboratory Biology, Cell Biology
Origin of sarcomere:
one of the segments into which a myofibril is divided
The contractile unit of the myofibril of a striated muscle.
A Sarcomere' is the basic unit of a muscle. Muscles are composed of tubular muscle cells which are formed in a process known myogenesis. Muscle cells are composed of tubular myofibrils. Myofibrils are composed of repeating sections of sarcomeres, which appear under the microscope as dark and light bands. Sarcomeres are composed of long, fibrous proteins that slide past each other when the muscles contract and relax. Two of the important proteins are myosin, which forms the thick filament, and actin, which forms the thin filament. Myosin has a long, fibrous tail and a globular head, which binds to actin. The myosin head also binds to ATP, which is the source of energy for muscle movement. Myosin can only bind to actin when the binding sites on actin are exposed by calcium ions. Actin molecules are bound to the Z line, which forms the borders of the sarcomere. Other bands appear when the sarcomere is relaxed. A muscle cell from a biceps may contain 100,000 sarcomeres. The myofibrils of smooth muscle cells are not arranged into sarcomeres.
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