Muscle Contraction

muscle contraction: physical interaction of protein filaments required for muscle function

\ muscle activity: response to input from the nervous system. action is always to contract, extension is passive

\ vertebrate skeletal muscle: moves bones and the body, characterized by a hierarchy of smaller and smaller units

thin filaments: consists of two strands of actin and two strands of a regulatory protein

thick filaments: staggered arrays of myosin molecules

actin: a protein that forms (together with myosin) the contractile filaments of muscle cells, and is also involved in motion in other types of cells

myosin: a fibrous protein that forms (together with actin) the contractile filaments of muscle cells and involved in motion in other types of cells

sarcomere: functional unit of a muscle

tropomyosin: a protein involved in muscle contraction related to myosin and occurs together with troponin in the thin filaments of muscle tissue

two basic mechanisms by which nervous system produces graded contractions: varying the number of fibers that contract, varying the rate at which fibers are stimulated

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