The order of recruitment of motor units is directly related to the size of

The order of recruitment of motor units is directly

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The order of recruitment of motor units is directly related to the size of their motor neuron. Motor units with smaller motor neurons will be recruited first. Size of motor units Stimulation threshold
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Larger motor neurons require higher stimulation to be recruited Current leak Dilution Cytoplasmic resistance same stimulation different response upper motor neuron lower motor neuron 1 lower motor neuron 2
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Speed of movement = speed of power stroke cycle determined by speed of myosin ATPase activity
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Muscle cell Heterogeneity in a Skeletal Muscle Oil Red O NADH staining ATPase at pH 4.6 MHC II MHC-I Myosin heavy chain isotypes Transverse section examination There are mainly two distinct types of muscles, they are named Type I and Type II. Type II has several subtypes: a, b, and x. All classification is based on myosin heavy chain isoforms expressed.
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Distinct Properties of Type I & Type II Muscle Fibers Characteristics Type I Type II (a, b, x) Molecular & Cellular Metabolism MHC human gene MYH 7 MYH 1, 2, 4 Myosin ATPase activity Low High Mitochondria density High Medium-low Main fuel storage Fat Carbohydrates Myoglobin (red) Yes No Oxygen usage Aerobic
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  • Fall '18
  • Afrifa
  • Motor neuron, Type II Muscle Fibers

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