| muscle fibre | <pathology> Component of a skeletal muscle comprising a single syncytial cell that contains myofibrils. Any of the cells of skeletal or cardiac muscle tissue. Skeletal muscle fibres are cylindrical multinucleate cells containing contracting myofibrils, across which run transverse striations, enclosed in a sarcolemma. Cardiac muscle fibres contain one or sometimes two nuclei and myofibrils and are separated from one another by an intercalated disk; although striated, cardiac fibres branch to form an interlacing network. 2. fast-twitch muscles. Skeletal muscle fibres having high myofibrillar atpase activity, high glycolytic enzyme activities, and an intermediate glycogen content which produce a fast twitch. There are two types. Fast fatigable fibres, also called white fibres, have a low myoglobin content, and a small mitochondrial content, and fatigue rapidly due to their limited glycogen content and low capacity for oxidative metabolism. Fast fatigue-resistant fibres, also called red fibres, have a large mitochondrial content and a high myoglobin content, related to their resistance to fatigue. 3. slow-twitch muscles. Skeletal muscle fibres having low myofibrillar atpase activity, low glycogen content, and high myoglobin content, high mitochondrial oxidative enzyme activities, and an intermediate mitochondrial content which produce a slow twitch and are fatigue-resistant. (12 Dec 1998) |
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| muscle haemoglobin | <physiology> Protein (17.5 kD) found in red skeletal muscle. It was the first protein for which the tertiary structure was determined by X-ray diffraction, by J.C.Kendrew's group working on sperm whale myoglobin. It is a single polypeptide chain of 153 amino acids, containing a haem group bonded via its ferric iron to two histidine residues. It binds oxygen noncooperatively and has a higher affinity for oxygen than haemoglobin at all partial pressures. In capillaries oxygen is effectively removed from haemoglobin and diffuses into muscle fibres where it binds to myoglobin which acts as an oxygen store. (18 Nov 1997) |
| muscle hypertonia | <neurology, physiology> Abnormal increase in muscle tone. (12 Dec 1998) |
| muscle hypotonia | <neurology, physiology> A diminution of the skeletal muscle tone with a diminished resistance to passive stretching. (12 Dec 1998) |
| muscle neoplasms | Neoplasms located in muscle tissue or specific muscles. They are differentiated from neoplasms, muscle tissue which are neoplasms composed of skeletal, cardiac, or smooth muscle tissue, such as myosarcoma or leiomyoma. (12 Dec 1998) |
| muscle of antitragus | <anatomy> A band of transverse muscular fibres on the outer surface of the antitragus, arising from the border of the intertragic notch and inserted into the anthelix and cauda helicis. Synonym: musculus antitragicus, muscle of antitragus. (05 Mar 2000) |
| muscle of heart | muscle |
| muscle of notch of helix | An occasional muscle on the cranial surface of the auricle spanning the antitragohelicine fissure. Synonym: musculus incisurae helicis, musculus intertragicus. (05 Mar 2000) |
| muscle of tragus | <anatomy> A band of vertical muscular fibres on the outer surface of the tragus of the ear. Synonym: musculus tragicus, muscle of tragus, Valsalva's muscle. (05 Mar 2000) |
| muscle of uvula | <anatomy, muscle> Origin, posterior nasal spine; insertion, forms chief bulk of the uvula; action, raises the uvula; nerve supply, pharyngeal plexus. Synonym: musculus uvulae, muscle of uvula, musculus azygos uvulae, palatouvularis muscle, uvularis. (05 Mar 2000) |
| muscle phosphorylase deficiency | Type V glycogen storage disease, affecting muscle, caused by deficiency of muscle phosphorylase. (05 Mar 2000) |
| muscle plasma | An alkaline fluid in muscle that is spontaneously coagulable, separating into myosin and muscle serum. (05 Mar 2000) |
| muscle plate | <anatomy> A muscular segment; one of the zones into which the muscles of the trunk, especially in fishes, are divided; a myocomma. One of the embryonic muscular segments arising from the protovertebrae; also, one of the protovertebrae themselves. The muscular system of one metamere of an articulate. See: Myotomy. Source: Websters Dictionary (01 Mar 1998) |
| muscle proteins | The protein constituents of muscle, the major ones being actins and myosin. More than a dozen accessary proteins exist including troponin, tropomyosin, and dystrophin. (12 Dec 1998) |
| muscle relaxant | <pharmacology> An agent that specifically AIDS in reducing muscle tension, as those acting at the polysynaptic neurons of motor nerves (for example meprobamate) or at the myoneural junction (curare and related compounds). Origin: L. Relaxare = to loosen (18 Nov 1997) |