Anatomy of Muscle Spindle o Primary sensory endings Type la fibers o Stimulated by both the rate and amount of stretch ynamic response u 400 Steady state 200 response E 0 6 5 mm/sec 15 mm/sec 30 mm/sec 1 sec
Anatomy of Muscle Spindle ⚫ Primary sensory endings – Type Ia fibers ⚫ Stimulated by both the rate and amount of stretch
Anatomy of Muscle Spindle o Secondary sensory endings Type II fibers o stimulated only by degree of stretch 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
Anatomy of Muscle Spindle o The contractile region of the intrafusal muscle fibers are limited to their ends as only these areas contain actin and myosin filaments o These regions are innervated by gamma (r) 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 as only these areas contain actin and myosin filaments ⚫ These regions are innervated by gamma () efferent fibers
la afferent Muscle stretch reflex Quadriceps Alpha motor neuron spindle Tendon of q
Muscle stretch reflex
(2)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-Proprioceptor nerve fiber dorsal root of the spinal cord -synapses with anterior motor neurons→0- motor n.F→ the same m.from whence the M. spindle fiber originated
(2) 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 Proprioceptor 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