1. muscle fibers- A cylindrical, multinucleate cell composed of numerous myofibrils that contracts when stimulated. 2. skeletal muscle fibers- muscle composed of cylindrical multinucleate cells with obvious striations. 3. striated muscle-muscle consisting of cross striated muscle fibers, including cardiac and skeletal muscle. 4. voluntary muscle-skeletal muscle 5. endomysium- The connective tissue layer surrounding an individual skeletal muscle 6. perimysium- the connective enveloping bundles of muscle fibers. 7. fascicle-a bundle of nerve or muscle fibers bound together by connective tissue. 8. epimysium- the sheath of fibrous connective tissue surrounding a muscle. 9. tendons- cord of dense fibrous tissue attaching a muscle to a bone. 10. aponeuroses- fibrous or membranous sheet connecting a muscle and the part it moves. 11. smooth muscle- muscle consisting of spindle shaped, unshaped (nonstriated) muscle cells; involuntary muscle. 12. cardiac muscle- The specialized striated muscle tissue of the heart; the myocardium. 13. sarcolemma- A thin membrane enclosing a striated muscle fiber. 14. myofibrils- found in cytoplasm of muscle cells.Any of the threadlike fibrils that make up the contractile part of a striated muscle fiber. 15. light (I) bands- the band within a striated myofibril. 16. dark (A) bands- The A bands are bisected by the H zone running through the center of which is the M line. 17. sarcomeres- the smallest contractile unit of muscle, extends form one Z disc to the next. 18. myofilaments- filaments composing the myofibrils. Of two types, actin and myosin. 19. thick filaments- Thick filaments in striated muscle are myosin polymers with a length and diameter that depend on the fiber type. 20. myosin- responsible for actin-based motility. 21. cross bridges- the globular head of a myosin molecule that projects from a myosin filament inmuscle and in the sliding filament hypothesis of muscle contraction is held to attach temporarily to an adjacent actin filament and draw it into the A band of a sarcomere between the myosin filaments 22. thin filaments - a myofilament of the one of the two types making up myofibrils that is about 5 nanometers (50 angstroms) in width and iscomposed chiefly of the protein actin 23. actin - a protein found especially in microfilaments (as those comprising myofibrils) andactive in muscular contraction, cellular movement, and maintenance of cell shape 24. sarcoplasmic reticulum (SR) - the endoplasmic reticulum of cardiac muscle and skeletal striated muscle that functions especially as a storage andrelease area for calcium 25. motor unit - a motoneuron together with the muscle fibers on which it acts 26. axon - a usually long andsingle nerve-cell process that usually conducts impulses away from the cell body 27. axon terminals - The somewhat enlarged, often club-shaped endings by which axons make synaptic contacts with other nerve cells or with effector cells. Also called end-feet, neuropodia, terminal boutons. 28. neuromuscular junction - the junction of an efferent nerve fiber and the muscle fiber plasma membrane called also myoneural junction 29. synaptic cleft - the space between neurons at a nerve synapse across which a nerve impulse is transmitted by a neurotransmitter called alsosynaptic gap 30. neurotransmitter - a substance (asnorepinephrine or acetylcholine) that transmits nerve impulses across a synapse 31. acetyl choline - a substance (asnorepinephrine or acetylcholine) that transmits nerve impulses across a synapse 32. action potential - the change in electrical potential that occurs between the inside and outside of a nerve or muscle fiber when it is stimulated, serving to transmit nerve signals. 33. graded responses - ability to contract to varying degrees. A muscle, like the biceps, contracts with varying degrees of force depending on the circumstance (ex. Graded responses). 34. muscle twitches - a small, local, involuntary muscle contraction (twitching) visible under the skin arising from the spontaneous discharge of a bundle of skeletal muscle fibers. Fasciculations have a variety of causes, the majority of which are benign, but can also be due to disease of the motor neurons 35. fused (complete) tetanus - Tetanus has to do with twitch contraction and the control of muscle tension in skeletal muscles. It is based on the rate at which a stimulus (impulse causing contraction) is delivered to a muscle fiber after the absolute refractory period (time where no contraction can occur) but before the muscle is relaxed. 36. unfused (incomplete) tetanus - If the muscle is stimulated at a lower rate at this point it will partially relax causing a wave in contractions. This is known as incomplete tetanus, or unfused tetanus. However, if the muscle is stimulated at a higher rate it can not relax at all, causing it to be contracted at all times (Complete, or fused tetanus). If you know anything about skeletal muscle contraction in terms of movement, this can cause a big problem due to the fact that while the agonist contracts, the antagonist relaxes allowing for the movement (ex. flexing your arm at the elbow). If you have complete tetanus both are contracting at the same time which can cause extreme pain. 37. creatine phosphate - a compoundC4H10N3O5P of creatine and phosphoric acid that is found especially in vertebrate muscle where it is an energy source for muscle contraction called alsocreatine phosphate 38. aerobic respiration - Respiration in which molecular oxygen is consumed and carbon dioxide and water are produced. 39. lactic acid - a hygroscopic organic acid C3H6O3 that is known in three optically isomeric forms: the dextrorotatory form present normally in blood and muscle tissue as a product of the anaerobic metabolism of glucose and glycogen b or lactic acid : the levorotatory form obtained by biological fermentation of sucrose c or lactic acid : the racemic form present in food products and made usually by bacterial fermentation (as of whey or raw sugar) but also synthetically, and used chiefly in foods and beverages, in medicine, intanning and dyeing, and in making esters for use as solvents and plasticizers 35&36 Frequency-Tension Relation Increase in muscle tension from successive action potentials is called summation and a maintained contraction in response to repetitive stimulation is called tetanus. If a tetanus oscillates, it is called infused tetanus while a tetanus without oscillations is called fused tetanus.
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