| actin | a structural protein of muscle that works with myosin in permitting muscular contraction.
|
 |
|
|
| concentric action | occurs when a muscle is activated and shortens.
|
|
|
|
| dynamic | refers to an isotonic muscle action.
|
|
|
|
| eccentric action | occurs when a muscle is activated and force is produced but the muscle lengthens.
|
|
|
|
| endomysium | the inner layer of connective tissue surrounding a muscle fiber.
|
|
|
|
| end-plate potential (EPP) | depolarization of a membrane region by a sodium influx.
|
|
|
|
| epimysium | the outer layer of connective tissue surrounding muscle.
|
|
|
|
| extensors | muscles that extend a limb--that is, increase the angle at a joint.
|
|
|
|
| fasciculi | a small bundle of muscle fibers.
|
|
|
|
| fast-twitch fibers | one of several types of muscle fibers found in skeletal muscle; also called Type II fibers; characterized as having low oxidative capacity but high glycolytic capacity.
|
|
|
|
| flexors | muscle groups that cause flexion of limbs--that is, decrease the angle at a joint.
|
|
|
|
| Golgi tendon organ (GTOs) | a tension receptor located in series with skeletal muscle.
|
|
|
|
| intermediate fibers | muscle fiber type that generates high force at a moderately fast speed of contraction, but has a relatively large number of mitochondria (Type IIa).
|
|
|
|
| isometric | action in which the muscle develops tension, but does not shorten; also called a static contraction. No movement occurs.
|
|
|
|
| lateral sac | see terminal cisternae.
|
|
|
|
| motor neurons | efferent neurons that conduct action potentials from the central nervous system to the muscles.
|
|
|
|
| motor unit | a motor neuron and all the muscle fibers innervated by that single motor neuron; responds in an "all-or-none" manner to a stimulus.
|
|
|
|
| muscle action | term used to describe muscle form development.
|
|
|
|
| muscle spindle | a muscle stretch receptor oriented parallel to skeletal muscle fibers; the capsule portion is surrounded by afferent fibers, and intrafusal muscle fibers can alter the length of the capsule during muscle contraction and relaxation.
|
|
|
|
| myofibrils | the portion of the muscle containing the thick and thin contractile filaments; a series of sarcomeres where the repeating pattern of the contractile proteins gives the striated appearance to skeletal muscle.
|
|
|
|
| myosin | contractile protein in the thick filament of a myofibril that contains the cross-bridge that can bind actin and split ATP to cause tension development.
|
|
|
|
| neuromuscular junction | synapse between axon terminal of a motor neuron and the motor end plate of a muscle's plasma membrane.
|
|
|
|
| perimysium | the connective tissue surrounding the fasciculus of skeletal muscle fibers.
|
|
|
|
| sarcolemma | the cell (plasma) membrane surrounding a muscle fiber.
|
|
|
|
| sarcomeres | the repeating contractile unit in a myofibril bounded by Z-lines.
|
|
|
|
| sarcoplasmic reticulum | a membranous structure that surrounds the myofibrils of muscle cells; location of the terminal cisternae or lateral sacs that store the Ca11 needed for muscle contraction.
|
|
|
|
| sliding filament model | a theory of muscle contraction describing the sliding of the thin filaments (actin) past the thick filaments (myosin).
|
|
|
|
| slow-twitch fibers | muscle fiber type that contracts slowly and develops relatively low tension but displays great endurance to repeated stimulation; contains many mitochondria, capillaries, and myoglobin.
|
|
|
|
| summation | repeated stimulation of a muscle that leads to an increase in tension compared to a single twitch.
|
|
|
|
| terminal cisternae | portion of the sarcoplasmic reticulum near the transverse tubule containing the Ca11 that is released upon depolarization of the muscle; also called lateral sac.
|
|
|
|
| tetanus | highest tension developed by a muscle in response to a high frequency of stimulation.
|
|
|
|
| transverse tubule | an extension, invagination, of the muscle membrane that conducts the action potential into the muscle to depolarize the terminal cisternae, which contain the Ca11 needed for muscle contraction.
|
|
|
|
| tropomyosin | protein covering the actin binding sites that prevents the myosin cross-bridge from touching actin.
|
|
|
|
| troponin | protein, associated with actin and tropomyosin, that binds Ca11 and initiates the movement of tropomyosin on actin to allow the myosin cross-bridge to touch actin and initiate contraction.
|
|
|
|
| twitch | the tension-generating response following the application of a single stimulus to muscle.
|
|
|
|
| Type I fibers | fibers that contain large numbers of oxidative enzymes and are highly fatigue resistant.
|
|
|
|
| Type IIa fibers | fibers that contain biochemical and fatigue characteristics that are between Type IIb and Type I fibers.
|
|
|
|
| Type IIb fibers | fibers that have a relatively small number of mitochondria, a limited capacity for aerobic metabolism, and are less resistant to fatigue than slow fibers.
|