Anatomy of Muscle Spindle o Secondary sensory endings Type II fibers o stimulated only by degree of stretch(static response) inear stretch Sinusoidal Release stretch Stimulus Pr mar MM山⊥Li Secondary 山⊥1
Anatomy of Muscle Spindle ⚫ Secondary sensory endings – Type II fibers ⚫ stimulated only by degree of stretch (static response)
Anatomy of Muscle Spindle o The contractile region of the intrafusal muscle fibers are limited to their ends only these areas contain actin and myosin filaments are innervated by gamma(y)efferent fibers la primary afferent from nuclear bag fiber 2 阝 efferent efferent To extra- lI secondary fusal fibers afferent Plate Annulospiral endings ending Nuclear bag fiber Nuclear chain fiber Trail ending Flower-spray ending
Anatomy of Muscle Spindle ⚫ The contractile region of the intrafusal muscle fibers are limited to their ends – only these areas contain actin and myosin filaments – are innervated by gamma () efferent fibers
la afferent 2 Muscle stretch reflex Quadriceps Alpha motor neuron spindle Tendon of q
2. Muscle stretch reflex
Muscle stretch reflex Definition: Whenever a muscle is stretched. excitation of the spindles causes reflexive contraction of the same muscle from which the signal originated and also of closely allied synergistic muscle The basic circuit: Spindle -la or Ii nerve fiber- dorsal root of the spinal cord -synapses with anterior motor neurons→α- motor n.F、 the same m. from whence the m spindle fiber originated
Muscle stretch reflex Definition: Whenever a muscle is stretched, excitation of the spindles causes reflexive contraction of the same muscle from which the signal originated and also of closely allied synergistic muscle. The basic circuit: Spindle Ia or II nerve fiber dorsal root of the spinal cord synapses with anterior motor neurons a -motor N. F. the same M. from whence the M. spindle fiber originated
Circuit of the Strength Reflex Sensory nerve Motor nerve pind Stretch reflex
Circuit of the Strength Reflex