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skeletal muscle fibers
long cylindrical cell with multiple oval nuclei arranged just beneath the sarcolemma
rod like fibers that run the length of the cell; contain contractile elements; 80% of cellular volume; made up of myofilaments
globular heads of myosin line the thick and thin elements together; allows contraction
comparable to the smooth endoplasmic reticulum; regulates intracellular levels of ionic calcium; stores and releases calcium at the correct times
elongated tube penetrating into the cell from the sarcolemma; the "telegraph system"; ensures every myofibril contracts at the same time
sliding filament model of muscle contractioin
thin filaments are pulled toward the sarcomere centers by cross bridge activity of the thick filament
location where the terminal portion of a motor neuron axon meets a muscle cell membrane
recruitment (staircase effect)
increased contraction in response to multiple stimuli of the same strength; increases availability of calcium in sarcoplasm; "warm-up" period for athletes
constant slightly contracted state of all muscles that does not produce movement; keeps the muscles firm, healthy and ready to respond
roles of ATP
1. transfers energy to myosin cross bridge to energize the power stroke; 2. disconnects the myosin cross bridge from the actin binding site; 3. fuels the pump that actively transports calcium ions to the sarcoplasmic reticulum
regeneration of ATP
1. interaction of ADP with creatine phosphate; 2. stored glycogen via anaerobic pathways, aka glycolysis; 3. aerobic respiration
physiological inability to contract due to shortage of ATP; results from ionic imbalance, lactic acid and lack of ATP
Duchenne Muscular Dystrophy
most common form of muscular dystrophy; inherited sex-linked disease carried by females and normally expressed in males; diagnosed between the ages of 2-10; victims become clumsy and fall frequently as their muscles fail; progresses from the extremeties upward and victims die of repiratory failure in their 20s; there is no cure
commonly called a pulled muscle; excessive stretching and possible tear of muscle due to overuse/ abuse
acute infectious disease resulting in painful spasms of skeletal muscles; eventually results in lock jaw and respiratory failure
oppose/reverse a particular movement; produce smooth, coordinated and precise movements with synegists
add extra force to the prime mover; reduce undesirable movements; also called fixators when they immobilize a bone or muscles origin
short, attach obliquely to a central tendon; look like a feather; ex. extensor digitorum
broad origin; fascicles converge toward a single tendon; triangular shape; pectoralis major
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