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15 Cards in this Set
- Front
- Back
- 3rd side (hint)
Define myograph
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an input transducer (or “force transducer”) commonly used to record muscle contraction
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Define myogram
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a physiological recording of muscle contraction
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Define muscle twitch
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a rapid, jerky, contractile response of a skeletal muscle when given a single stimulus of sufficient strength
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Define threshold stimulus
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the smallest stimulus that first causes contraction
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Define maximal stimulus
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minimal stimulus that first causes a maximal contractile response
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Define motor unit
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a motor neuron plus all the muscle fibers (muscle cells) it innervates
motor units vary in # of muscle fibers and the size of the fibers smaller motor units: have finer fibers; more easily stimulated larger motor units: have thicker fibers, respond later, producing a more forceful contraction |
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Define motor unit summation
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(recruitment): increasing the number of motor units contracting simultaneously producing a stronger contraction.
(Induced experimentally by increasing the amplitude of electrical stimulation). |
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Define mechanical summation
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Mechanical Summation (wave summation): increasing the frequency of stimulation, thereby increasing the rapidity of contraction producing a stronger contraction.
Allows for smooth continuous contraction). Both types of summation occur together in the grading of contractile responses. |
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Define tetanus
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Tetanus: complete fusion of individual twitches, resulting in a continued state of contraction
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Define fatigue
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the decline in muscle tension as a result of previous contractile activity
Neuromuscular fatigue: caused by shortage of neurotransmitter (not likely to occur in our frog gastrocnemius lab exercise) Mechanical fatigue: actual mechanism not totally clear. May be caused by: - build-up of lactic acid, lowering pH and interfering with enzymatic activity - from a relative deficit of ATP which somehow affects the excitation- contraction coupling mechanism |
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Define muscle tone
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a sustained partial contraction of portions of a skeletal muscle in response to activation of stretch receptors (due to asynchronous motor unit stimulation)
• stabilizes the position of bones and joints • allows the skeletal muscles to act as a shock absorbers that cushion sudden bumps |
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Define treppe
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when a skeletal muscle contracts more forcibly in response to the same strength of stimulation after it has contracted many times (not summation, relaxation occurs between each stimulation); May be caused by:
• priming the external cytosol with Ca++ • tightens up the slack due to the elastic series component (ESC) • increase in temperature, increases enzymatic activity |
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Define an isotonic contraction
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- in isotonic contractions, cross-bridge activity leads to a shortening of the sarcomeresIsotonic Contraction
1. Muscle shortens 2. Tension is constant 3. Energy is expended 4. Graph: Distance vs. Time |
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Define an isometric contraction
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- in isometric contractions, cross-bridge activity leads to development of tension in the sarcomeresIsometric Contraction
1. Muscle does not shorten (change length) 2. Tension increases 3. Energy is expended 4. Graph: Tension vs. Time |
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Describe the function of the myograph transducer and how it was calibrated.
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an input transducer used to record movement during muscle contraction
used a weight to calibrate |
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