click below
click below
Normal Size Small Size show me how
anatomy
Term | Definition |
---|---|
Excitability | ability to be stimulated |
Contractility | ability to contract, or shorten, and produce body movement |
Extensibility | ability to extend, or stretch, thereby allowing muscles to return to their resting length |
T tubules | Transverse tubules extend across the sarcoplasm at right angles to the long axis of the muscle fiber b. Formed by inward extensions of the sarcolemma c. Membrane has ion pumps that continually transport Ca⫹⫹ ions inward from the sarcoplasm d. Allow electr |
Sarcoplasmic reticulum | Network of tubules and sacs found within muscle fibers b. Membrane of the SR continually pumps calcium ions from the sarco-plasm and stores the ions within its sacs for later release |
Triad | Triplet of tubules; a T tubule sandwiched between two sacs of sarco-plasmic reticulum b. Allows an electrical impulse traveling along a T tubule to stimulate the membranes of adjacent sacs of the sarcoplasmic reticulum |
Myofibrils | —numerous fine fibers packed close together in sarcoplasm |
Sarcomere | Segment of myofibril between two successive Z disks b. Each myofibril consists of many sarcomeres c. Contractile unit of muscle fibers |
Striated muscle | Dark stripes called A bands; light H band runs across the midsection of each dark A band b. Light stripes called I bands; dark Z disk extends across the center of each light I band |
Myofilaments | Each myofibril contains thousands of thick and thin myofilaments 2. Four different kinds of protein molecules make up myofilaments |
Myosin | Makes up almost all the thick filament (2) Myosin “heads” are chemically attracted to actin molecules (3) Myosin “heads” are known as cross bridges when attached to actin |
Actin | globular protein that forms two fibrous strands twisted around each other to form the bulk of the thin filamen |