| A | B |
|---|
| actin | A protein involved in muscular contraction; the "water" of the contraction; 2 strands arranged in a double helix; anchored at the z-lines |
| concentric action | Muscle action in which the ends of the muscle are drawn closer; the total tension developed in all cross-bridges of a muscle is sufficient to overcome any resistance to shortening |
| cross-bridge | Extensions of myosin; the "oars"; the energy for cross-bridge flexion comes from the hydrolysis (breakdown) of ATP and ADP; another molecule of ATP must replace the ADP on the myosin cross-bridge head for the head to detach from the actin active site and recock. |
| distal | Farther from the trunk (one of the limb muscle attachments) |
| eccentric action | Muscle action in which a force external to the muscle overcomes the muscle force and the ends of the muscle are drawn further apart |
| endomysium | Surrounds each muscle fiber which encircles and is continuous with the fiber's membrane; is continuous with the tendon |
| epimysium | Fibrous connective tissue that covers the body's more than 430 skeletal muscles; is continuous with the tendons at the ends of the muscle; is continuous with the tendon |
| fasciculus | Bundles of muscle fibers under the epimysium that may consist of up to 150 fibers |
| inferior | Closer to the feet (one of the trunk muscle attachments) |
| insertion | The muscle attachment of the muscle that is more distal or inferior |
| isometric action | Muscle action in shich the ends of the muscle are prevented from drawing closer together, with no change in length |
| length-tension relationship | The amounth of force that a muscle can exert is related to its length; peak force production is usually seen at resting or slightly greater than resting length |
| motor unit | A motor neuron and the muscle fibers it innervates; all the muscle fibers of one of these contract together when they are stimulated by the motor neuron |
| muscle fiber | Muscle cells; long (sometimes running the entire length of a muscle), cylindrical (about the diameter of a human hair) cells; have many nuclei situated on the periphery of the cell and have a striated appearance under low magnification |
| myofibril | contain the apparatus that contracts the muscle cell; is about 1/100 the diameter of a hair and contain the apparatus that contracts the muscle cell, which consists primarily of two types of myofilaments: myosin and actin |
| myofilament | Contractile proteins (actin and myosin) located within muscle myofibrils |
| myosin | A protein involved in muscular contraction; the "oars" of the contraction are at the end of the tail |
| neuromuscular junction | The junction between a motor neuron 9nerve cell) and the muscle fibers it innervates; motor end plate; each muscle cell has only one |
| origin | The attachment of the muscle that is more proximal or superior |
| permysium | connective tissue that surrounds the fasciculi; is continuous with the tendon |
| periosteum | A specialized connective tissue covering all bones where tendons are attached |
| proximal | closer to the trunk (one of the limb muscle attachments) |
| sarcolemma | The muscle fiber's membrane; is continuous with the edomysium |
| sarcomere | The distance between two z lines; the smallest contractile unit of skeletal muscle |
| sarcoplasm | the cytoplasm of a muscle fiber; contains contractile components, shich consist of protein filaments; other proteins; sotred glycogen and fat particles; enzymes; and specialized structures such as mitochondria and the sarcoplasmic reticulum |
| sarcoplasmic reticulum | A network of tubules and vesicles surrounding the myofibril; is stiumlated to release calcium ions |
| sliding-filament theory | A proposed mechanism for muscle action where shortening and elongation are the result of actins sliding inward and outward over myosins |
| stretch-shortening cycle | increase in force production; prestreching a muscle joint prior to a concentric action can enhance force prodction druing the subsequent contraction; possible cause by the combined effects of the use of elastic energy in the muscle and stretch-reflex potentiation; stretching a two-joint muscle at one joint may increase the muscle's ability to generate force at the other joint (hamstring and hip/knee) |
| superior | closer to the head (one of the trunk muscle attachments) |
| triad | The pattern of a T-tubule spaced between ad perpendicular to two sarcoplasmic reticular vesicles |
| tropomyosin | A protein involved in muscular contration; a shift occurs in these molecules after the cross-bridges attach to the actin filament, at the troponin, which runs along the length of the actin filament in the groove of the double helix |
| troponin | A protein involved in muscular contraction; situated at regular intervals along the actin filament and has a high affinity for calcuium inos |
| T-tubule | Invaginations of the sarcolemma that function as part of the sarcoplasmic reticulum; also called transverse tubules; run perpendicular to the sarcopalsmic reticulum and terminate in the vicinity of the z-line and between two vesicles |
| calcium | binds with the troponin molecule in the contraction process; also plays a role in regulating a large number of events in skeletal muscle besides contraction...glycolytic and oxidative energy metabolism protein syntehesis and degradation |
| 1st event of muscle shortening | binding of calcium to troponin |
| 2nd event of muscle shortening | coupling of the myosin cross-bridge with actin |
| 3rd event of muscle shortening | cross-bridge flexion |
| 4th event of muscle shortening | dissociation of actin and myosin |
| 5th event of muscle shortening | recocking of the myosin cross-bridge head |
| muscle shortening only can occur when | calcium is available in the myofibril, ATP is available to assist in uncoupling the myosin from the actin, and sufficient active myosin ATPase is available for catalysing the breakdown of ATP |
| muscle at rest | little calcium present in myofibril so very few of the myosin cross-bridges are bound to actin |
| preloading | high tension is developedi n muscle even before movement occurs when lifting weights because the wieghts must be supported isometrically |
| hydraulic and isokinetic systems | do not load the muscle prior to the contraction; |
| Angle of pennation | can affect the number of sarcomeres per cross-sectional area and thus the maximal force capabilities; muscles with greater pennation have more sarcomeres in parallel and fewer sarcomeres in seires; theyare are better able to geerate force but have a lower shortening velocity than non-pennate muscle |
