Muscle Receptors and spinal reflexes

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Muscle Receptors and spinal reflexes

• Stuart Binder-Macleod, PT, PhD, FAPTA

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Objective 1

• Outline the structural and functional
  characteristics of the muscle spindle, including
• -the relationship of the muscle spindle to the
  extrafusal muscle fibers
• -morphology of the spindle
• -response of the intrafusal fibers to fusimotor
  stimulation
• -CNS connections

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Muscle Spindle
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Muscle Spindle
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Ms Spindle - CNS Connections
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Objective 2

• Identify the response of the primary and
  secondary endings to
• -muscle length
• -rate of change in muscle length
• -extrafusal muscle contraction
• -fusimotor stimulation
• -fusimotor stimulation combined with stretch

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Ms Spindle - Responses
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Ms Spindle - Responses
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Ms Spindle - Responses
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Objective 3

• Outline the structural and functional
  characteristics of the Golgi Tendon Organ (GTO),
  including
• -relationship to the muscle tendon
• -morphology of the GTO
• -differential response characteristics of the GTO
  to active and passive tension
• -CNS connections

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GTO
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GTOs Central Connections
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Withdrawal Reflex
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Objective 4

• Discuss the possible roles that muscle spindles
  and the GTOs may play in normal motor control

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Ms Spindle - CNS Connections
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Objective 5

• Identify the possible mechanisms by which
  alterations in the input from either the muscle
  spindle or GTO could produce disturbances in
  muscle tone

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Clinical Model Stretch Reflexes

• LH is a 59 year old male who had a stroke 14
  months ago primarily affecting the right side of
  his body. He has had good motor and sensory
  return to his lower extremity and is able to walk
  to for moderate distances in the community with
  just the use of a straight cane. In contrast, he
  has marked motor and sensory deficits to his
  right upper extremity, particularly affecting the
  use of his hand. He has minimal voluntary active
  finger and thumb extension, markedly increased
  DTRs of his elbow and wrist flexors and
  extensors, and increased resistance to passive
  stretching of his elbow, wrist, and finger
  flexors, which is velocity dependent. You also
  note marked flexion posturing of his right upper
  extremity when he walks and during resistance
  exercises to his left upper extremity.

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Objective 6

• Identify possible therapeutic interventions that
  may be used to alter the clinical models tone or
  motor control and provide the rationale for their
  use.