Chapter 8 - Chapter 8 Control of Movement Muscles 3 types...

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Unformatted text preview: Chapter 8 Control of Movement Muscles 3 types of muscles: Skeletal muscles move us (and our bones) around; attached to bones, fastened via tendons, which are sting bands of connective tissue Flexion contraction of a flexor muscle, bending the joints Extension contraction of an extensor muscle, straitening the joints Anatomy of skeletal muscle Extrafusal muscle fibers responsible for force exerted by contraction of skeletal muscle; served by axons of alpha motor neurons Intrafusal muscle fibers (a.k.a. muscle spindles) contain sensory endings sensitive to stretch; served by axons of gamma motor neurons An alpha motor neuron, its axon, and the several extrafusal muscles fibers it innervates constitute a motor unit A single muscle fiber consist of bundle of myofibrils , each containing the proteins actin and myosin , which serve to contract the muscle; where these protein filaments overlap, the muscle appears to be striated, or striped, thus referred to as striated muscle Muscles Skeletal muscles (cont) The physical basis of muscular contraction The synapse b/t the axon of an efferent neuron and the muscle fiber it innervates is called the neuromuscular junction The terminal buttons synapse onto motor endplates , which are located in grooves on the muscle fibers ACh is released into the neuromuscular junction to depolarize the postsynaptic membrane this is called an endplate potential (much larger than EPSPs; always causes muscle fiber to fire, causing a twitch) Depolarization causes the actin and myosin filaments to work together (see rowing movement figure in book, Fig 8.2) to contract or shorten the muscle fiber A single impulse from motor neuron produces a single twitch of muscle fiber, with the strength of the contraction determined by rate of firing of motor units Muscles Skeletal muscles (cont) Sensory feedback from muscles The afferent stretch receptors of the intrafusal muscle fibers serve to detect muscle length Located within the tendon, in the Golgi tendon organ , and encode the degree of stretch by rate of firing The Golgi tendon organs detect the strength of the muscle contraction, and thus fire in proportion to the stress on the muscle...
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This note was uploaded on 07/31/2011 for the course PSB 3004 taught by Professor Williams during the Spring '08 term at University of Florida.

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Chapter 8 - Chapter 8 Control of Movement Muscles 3 types...

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