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Cards In This Set
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What does a transducer do?
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It converts the signal of interest (ex: blood pressure) into an analog voltage.
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What does EMG stand for?
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Electromyogram
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What makes up a motor unit?
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The motor neuron and all the individual muscle fibers it innervates
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What is isometric muscle contraction?
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The muscles contract but the joints do not move and muscle fibers maintain a constant length
"same measure" |
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What is isotonic muscle contraction?
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A body part is moved and the muscle fibers shorten or lengthen
"same tension" |
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What does CMP stand for and what does it mean?
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CMP = compound muscle potential
It is the sum of the electrical activity of many individual muscle fibers all firing at once. The magnitude of the CMP reflects the number of active motor units. |
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What is a muscle twitch?
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The response of a motor unit to a singel action potential of a motor neuron. It is a brief contraction.
**also called a tetanic contraction** |
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What is "recruitment"?
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One of the two ways to regulate muscle contraction:
Adjusting the number of motor axons firing to control the number of twitching muscle fibers. |
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What is "frequency modulation"?
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One of the two ways to regulate muscle contraction:
Vary the frequency of action potentials in the motor axons: the higher the stimulus, the more frequent the action potentials. |
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What is "coactivation"?
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A phenomenon in which contraction of a muscle leads to more minor activity in the antagonistic muscle.
It helps stabilize the joint. Ex: biceps and triceps |
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What is "summation"?
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When a stimulus is added before the muscle fiber is completely relaxed, the next contraction is stronger than normal.
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What is "tetanus"?
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At very high stimulation frequencies, the muscle has no time to relax between successive stimuli. The result is a smooth contraction many times stronger than a single twitch (tetanic contraction). It is now in a state of "tetanus".
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What is the Size Principle?
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It is a reflection of tension and time. The amount of tension a motor unit can handle over a period of time is directly proportional to its size. The larger motor units can handle more tension for longer.
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What is pseudo-fatigue and what are some explanations behind it?
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Pseudo-fatigue resembles fatigue because there is a declining force exerted while the person's eyes are shut. Losing the sense of sight puts you at a disadvantage because you can't read the monitor while you are exerting the force. Also, concentration may drift to other things while your eyes are closed.
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Why is the EMG waveform irregular, but the waveforms from an electrocardiogram are not?
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Unlike cardiac muscle, skeletal muscle does not contract in a fully synchronized fashion. Instead, an EMG is recording the unsynchronized electrical activity of many muscle fibers.
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