Motor Unit Structure & All-or-None Principle
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Questions and Answers

What does a motor unit consist of?

  • Only muscle fibers that contract independently
  • Sensory neurons and muscle fibers
  • The anterior motor neuron and specific muscle fibers it innervates (correct)
  • Multiple motor neurons and muscle fibers
  • How does the number of muscle fibers per motor neuron relate to a muscle's function?

  • It generally relates to how much strength is needed
  • The number is constant regardless of function
  • It generally relates to the muscle's particular movement function (correct)
  • It generally increases with greater precision of movement required
  • What is the All-or-None Principle in relation to motor units?

  • All muscle fibers in a motor unit contract or none do (correct)
  • Motor units can vary in their contraction strength
  • Some muscle fibers may contract while others do not
  • A stronger stimulus causes a stronger contraction
  • What is true about muscle fibers receiving input from a motor neuron?

    <p>Generally, each muscle fiber receives input from only one motor neuron</p> Signup and view all the answers

    Which statement best describes motor neurons' ability to control muscle contractions?

    <p>Motor neurons must either fully stimulate or not stimulate muscle fibers.</p> Signup and view all the answers

    Study Notes

    Motor Unit Structure

    • Motor unit comprises the anterior motor neuron and the specific muscle fibers it innervates.
    • Each muscle fiber typically receives input from only one neuron.
    • However, a single motor neuron can innervate multiple muscle fibers.
    • The number of muscle fibers per motor neuron is related to the muscle's function.
    • Muscles demanding less precision have hundreds of fibers per motor neuron.
    • Muscles requiring fine control have one muscle fiber per motor neuron.

    All-or-None Principle

    • Sufficient stimulus to trigger an action potential in the motor neuron causes all muscle fibers in the motor unit to contract simultaneously.
    • No partial activation of muscle fibers is possible.
    • A motor unit generates either full contraction or no contraction, no gradation of force.
    • Stronger action potentials do not produce stronger contractions within a single motor unit.

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    Description

    This quiz explores the structure of motor units and the all-or-none principle in muscle contraction. You will learn about the relationship between motor neurons and muscle fibers, as well as how action potentials lead to muscle contraction. Test your understanding of muscle physiology concepts!

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