| muscle cell | <cell biology, pathology> Cell of muscle tissue, in striated (skeletal) muscle it comprises a syncytium formed by the fusion of embryonic myoblasts, in cardiac muscle a cell linked to the others by specialise d junctional complexes (intercalated discs), in smooth muscle a single cell with large amounts of actin and myosin capable of contracting to a small fraction of its resting length. (07 Apr 1998) |
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| muscle, central core disease of | One of the conditions that produces 'floppy baby' syndrome. Ccd causes hypotonia (inadequately toned muscles characterised by floppiness) in the newborn baby, slowly progressive muscle weakness, and muscle cramps after exercise. Muscle biopsy shows a key diagnostic finding (absent mitochondria in the centre of many type i muscle fibres). Ccd is inherited as a dominant trait. The ccd gene is on chromosome 19 (and involves ryanodine receptor-1). (12 Dec 1998) |
| muscle contraction | A process leading to shortening and/or development of tension in muscle tissue. Muscle contraction occurs by a sliding filament mechanism whereby actin filaments slide inward among the myosin filaments. (12 Dec 1998) |
| muscle curve | <investigation, physiology> A test which measures muscle response to nerve stimulation. Used to evaluate muscle weakness and to determine if the weakness is related to the muscles themselves or a problem with the nerves that supply the muscles. Abnormal results may be seen in myasthenia gravis, polymyositis, carpal tunnel syndrome, amyotrophic lateral sclerosis, alcoholic neuropathy, cervical spondylosis, dermatomyositis, familial periodic paralysis, Guillain-Barre syndrome, Lambert-Eaton syndrome, Friedreich's ataxia, mononeuritis multiplex, peripheral neuropathy, sciatic nerve disease and a variety of peripheral nerve disorders. (27 Sep 1997) |
| muscle denervation | The resection or removal of the innervation of a muscle or muscle tissue. (12 Dec 1998) |
| muscle epithelium | Spindle-shaped, contractile, smooth muscle-like cells of epithelial origin that are arranged longitudinally or obliquely around sweat glands and the secretory alveoli of the mammary gland; stellate myoepithelial cells occur around lacrimal and some salivary gland secretory units. Synonym: muscle epithelium. Origin: myo-+ epithelium (05 Mar 2000) |
| muscle fascicle | A bundle of muscle fibres surrounded by perimysium. (05 Mar 2000) |
| muscle fatigue | <physiology> A condition resulting from prolonged and strong contraction of a muscle. Studies during prolonged submaximal exercise have shown that muscle fatigue increases in a near direct proportion to the rate of muscle glycogen depletion. Muscle fatigue in short-term maximal exercise is associated with oxygen deprivation and an increased level of blood and muscle lactic acid, and an accompanying increase in hydrogen-ion concentration in the exercised muscle. (12 Dec 1998) |
| 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) |
| 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 |