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The Motor Unit

Stimulation of a muscle by a nerve impulse is required before a muscle can shorten and produce movement. The Motor Unit. How the Nervous System works with the Muscular System to produce movement. Motor Unit Parts. Motor neuron A specialized nerve that transmits an impulse to a muscle

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The Motor Unit

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  1. Stimulation of a muscle by a nerve impulse is required before a muscle can shorten and produce movement. The Motor Unit How the Nervous System works with the Muscular System to produce movement

  2. Motor Unit Parts • Motor neuron • A specialized nerve that transmits an impulse to a muscle • Stimulates a muscle cell causing contraction • Neuromuscular junction • A specialized point of contact between a nerve ending and the muscle fiber it innervates • Chemicals are released in response to a nervous impulse that result in a contraction • Motor Unit • A single motor neuron with the muscle cell it innervates

  3. Muscle Stimulus • A muscle will contract ONLY if an applied stimulus reaches a certain level

  4. Threshold Stimulus • The minimal level of stimulation required to cause a muscle fiber to contract • All or None response • when threshold stimulus is reached, a muscle fiber contracts completely!

  5. Different muscle fibers in a muscle are controlled by different motor units having different threshold-stimuli levels • Individual muscle fibers always respond ALL or NONE to a threshold stimulus. • The muscle as a WHOLE does not • Posture • Tonic Contraction

  6. Different motor units responding to different threshold stimuli permit a muscle as a whole to execute contractions of graded force • The number of fibers stimulated determines the overall strength of the contraction

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