Lecture+22+Muscle+Physiology+Part+II

If relaxation phase disappears completely a

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If relaxation phase disappears completely, a contracture occurs. Repeated stimulation of muscle in time lessens its excitability and may result in muscle fatigue . Treppe 10 Saturday, June 18, 2011
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Tetanus refers to smooth and sustained muscular contractions. Multiple wave summation occurs when multiple twitch waves are added together to sustain muscle tension for a longer time. Incomplete tetanus occurs when very short periods of relaxation occur between peaks of tension. Complete tetanus occurs when the stimulation is such that twitch waves fuse into a single, sustained peak. Tetanus 13 Saturday, June 18, 2011
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Tonic contraction is the continual, partial contraction of a given muscle. At any one time, a small number of muscle fibers within a muscle contract, producing a tightness or muscle tone . Muscles with less tone than normal are referred to as flaccid . Muscles with more tone than normal are referred to as spastic . Muscle tone is maintained by negative feedback mechanisms. Muscle Tone 16 Saturday, June 18, 2011
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Skeletal muscles contract with varying degrees of strength at different times. Varying factors contribute to the phenomenon of graded strength . Dependent upon the metabolic condition of individual fibers. Number of muscle fibers contracting simultaneously; the greater the number of fibers contracting, the stronger the contraction. Dependent on the number of motor units recruited . Graded Strength Principle 18 Saturday, June 18, 2011
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The load imposed on a muscle influences the strength of a skeletal contraction. During the activation of a stretch reflex the body tries to maintain a constancy of muscle length in response to increased load. Maintains a relatively constant length as load is increased up to a maximum sustainable level.
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