Term
| Principles of Muscle Mechanics |
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Definition
1. same principles apply to contraction of a single fiber and a whole muscle
2. Contraction produces tension, the force exerted on the load or object to be moved
3. Contraction doesn't always shorten a muscle
4. force of duration of contraction vary in response to stimuli of different frequencies and intensities |
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Term
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Definition
| motor neuron and all (four to several hundred) muscle fibers it supplies |
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Definition
| muscles that control fine movements (fingers, eyes) |
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Term
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Definition
| large weight-bearing muscles (thighs, hips) |
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Term
| Muscle fibers from a motor unit |
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Definition
| are spread throughout the muscle so that a single motor unit that causes weak contraction of entire muscle |
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Definition
| usually contract asynchronously; helps prevent fatigue |
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Definition
| Response of a muscle to a single, brief threshold stimulus |
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Term
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Definition
| Latent period, Period of contraction, and period of relaxation |
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Term
| First stage of a twitch: Latent Period |
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Definition
| events of excitation-contraction coupling |
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Term
| Second stage of a twitch: Period of contraction |
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Definition
| cross bridge formation; tension increases |
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Term
| Third stage of a twitch: Period of relaxation |
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Definition
| CA2+ reentry into the SR; tension declines to zero |
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Term
| Muscle twitch comparisons |
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Definition
| Different strength and duration of twitches are due to variations in metabolic properties and enzymes between muscles |
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Term
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Definition
Variations in the degree of muscle contraction, Required for proper control of skeletal movement
Responses are graded by changing the frequency of stimulation, and changing the strength of the stimulus |
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Term
| Response to change in stimulus frequency |
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Definition
| a single stimulus results in a single contractile response- a muscle twitch, increase frequency of stimulus, Ca2+ release stimulates further contraction->temporal (wave) summation, Further increase in stimulus frequency->unfused (incomplete) tetanus |
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Term
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Definition
| stimulus strength at which the first observable muscle contraction occurs |
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Term
| Muscle contracts more vigorously as stimulus strength is |
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Definition
| increases above threshold |
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Definition
| is precisely controlled by recruitment(multiple motor unit summation), which brings more and more muscle fibers into action |
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Term
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Definition
| motor units with larger and larger fibers are recruited as stimulus intensity increases |
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Term
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Definition
| Constant, slightly contracted state of all muscles, due to spinal reflexes that activate groups of motor units alternately in response to input from stretch receptors in muscles, keeps muscles firm, healthy, and ready to respond |
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Term
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Definition
| Muscle changes in length and moves the load, either concentric or eccentric |
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Term
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Definition
| the load is greater than the tension the muscle is able to develop, tension increases to the muscle's capacity, but the muscle neither shortens nor lengthens |
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Term
| Available stores of ATP are depleted in |
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Definition
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Term
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Definition
| Direct phosphorylation of ADP by creatine phosphate, Anaerobic pathway (glycolysis), and aerobic respiration |
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Term
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Definition
| At 70% of maximum contractile activity; bulging muscles compress blood vessels, oxygen delivery is impaired, pyruvic acid is converted into lactic acid |
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Term
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Definition
| diffuses into the bloodstream, used as fuel by the liver, kidneys, and heart, and is converted back into pyruvic acid by the liver |
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Term
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Definition
| produces 95% of ATP during rest and light to moderate excercise, Fuels-> stored glycogen, then bloodborne glucose, pyruvic acid from glycolysis, and free fatty acids |
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Term
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Definition
| Physiological inability to contract, occurs when Ionic imbalances interfere with E-C coupling, and prolonged excercise damages the SR and interferes with Ca2+ regulation and release |
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Term
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Definition
| Extra O2 needed after exercise for replenishment of: oxygen reserves, glycogen stores, and ATP and CP reserves. also for conversion of lactic acid to pyruvic acid, glucose, and glycogen |
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Term
| Heat Production during muscle activity |
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Definition
| ~40% of the energy released in muscle activity is useful as work, remaining energy (60%) is given off as heat, and Dangerous heat levels are prevented by radiation of heat from skin and sweating |
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Term
| The force of contraction is affected by: |
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Definition
| Number of muscle fibers stimulated (recruitment) and relative size of the fibers- hypertrophy of cells increases strength, increased frequency allows time for more effective transfer of tension to noncontractile components |
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Term
| velocity and duration of contraction is influenced by: |
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Definition
| muscle fiber type (slow oxidative fibers, fast oxidative fibers, fast glycolytic fibers), load, and recruitment |
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Term
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Definition
| classified by: speed of contraction: slow or fast, according to: speed at which myosin ATPases split ATP and pattern of electrical activity of the motor neurons, and also by the metabolic pathways for ATP synthesis: oxidative fibers-use aerobic pathways, and glycolytic fibers use anaerobic glycolysis |
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Definition
| the greater the load, the greater the latent period, slower contraction, and decreased duration of contraction |
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Definition
| the more motor units that are contracting, the faster contraction and more prolonged the contraction |
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Term
| Aerobic (endurance) exercise |
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Definition
leads to increased:
muscle capillaries, number of mitochondria, and myoglobin synthesis
results in greater endurance, strength, and resistance to fatigue
may convert fast glycolytic fibers into fast oxidative fibers |
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Term
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Definition
| forcing a muscle to work hard promotes increased muscle strength and endurance, muscles adapt to increased demands, and muscles must be overloaded to produce further gains |
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