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Ch11 Musclar tissue3
All or Nothing Law
Question | Answer |
---|---|
If a muscle fiber is overly contracted at rest then... | upon stimulation the thick filaments can contract no farther than the Z discs and the contraction is weak |
If a muscle fiber is too stretched then... | upon stimulation there is little overlap between thick and thin filaments, and the myosin heads cannot get a good grip on the actin and the contraction is weak |
The amount of tension a muscle generates depends on... | how stretched or contracted it was before it was stimulated; this principle is termed the length–tension relationship |
Action potential | triggers the release of Ca2+ into the cytosol and activates the sliding filament mechanism. |
Twitch | At threshold or higher, a stimulus causes a quick cycle of contraction and relaxation of a muscle fiber. Produced by a single stimulus |
Treppe | Repeated stimulation after relaxation phase has been completed, causes higher tensions due to increased Ca2+ concentrations in the sarcoplasm |
During this time excitation, excitation–contraction coupling, and tensing of elastic components occurs during... | a latent period/delay |
In the body, the resisting load is usually a | bone |
Summation | Repeated stimulation before relaxation phase has been completed |
Wave summation (temporal summation) | when stimulation of a muscle fiber is fast enough one twitch is added to another (before complete relaxation takes place) |
Incomplete tetanus | when a muscle fiber reaches maximal tension and partially relaxes |
Complete tetanus | muscle fiber reaches maximal tension and stays contracted (relaxation phase is eleminated) |
Muscle tone is a result of... | Constant tension caused by changing activation of motor units. Thus, Stabilizes bones and joints |
Precise control of movement determined by... | number and size of motor unit |
One cause of treppe is that | the SR does not have time to completely reabsorb all the Ca+2 released. |
Isometric contraction | is contraction(rising tension) without a change in length & can maintain joint stability. |
Isotonic contraction | is contraction with a change in length but no change in tension & can move a load as the muscle shortens. |
Isotonic-concentric contraction | a muscle shortens as it maintains tension, such as when the biceps brachii contracts and flexes the elbow to lift a weight. |
Isotonic-eccentric contraction | a muscle lengthens as it maintains tension, such as when the biceps brachii lengthens as a weight is lowered |