Gamma Motor Neurones

• Muscle Spindle - Gamma Motor Neurones:

  • 2 types:
  • static gamma motor neurone
  • dynamic gamma motor neurone

  A) static gamma motor neurone

  B) dynamic gamma motor neurone

  
• Muscle Spindle - Gamma Motor Neurones:

  • they are a type of motor neurone - so take action potentials from motor neurones in the spinal cord, travel down and the axon enters the spindle
  • the axons innervate the striated muscle at the end of the spindles at neuromuscular junctions
  • neuromuscular junctions contain acetylcholine which, when released, can lead to contraction of a striated muscle
  • gamma motor neurones innervate the intrafusal muscle fibres

  A) static gamma motor neurone

  B) dynamic gamma motor neurone

  
• Muscle Spindle - Static Gamma Motor Neurones:

  • the static gamma motor neurones innervate the nonadaptive fibres:
  • static bag fibres
  • chain fibres

  A) static gamma motor neurone

  B) static bag

  C) chain

  
• Muscle Spindle - Dynamic Gamma Motor Neurones:

  • the dynamic gamma motor neurones innervate the adaptive fibres:
  • dynamic bag fibres

  A) dynamic gamma motor neurone

  B) dynamic bag

  
• Muscle Spindle - Gamma Motor Neurones overview pt1:

  • a system where specialist motor neurones are able to contract the entire intrafusal muscle fibre, shortening both ends, causing the central portion of the intrafusal fibres to tension up
  • so the gamma motor neurones are a system that allow us to alter the level of tension on the central portion of intrafusal fibres

  
• Muscle Spindle - Gamma Motor Neurones pt2:

  • this is important as it means we have a system that can alter the sensitivity of the muscle spindle - frequency of action potentials being generated is related to amount of tension - amount of tension is related to 2 things:
  • if spindle is lengthened, intrafusal fibres will be tensioned, causes action potentials
  • gamma motor neurones activate striated muscles at ends - can tension up the central portion of intrafusal fibres, causes action potentials

  
• Muscle Spindle - Gamma Motor Neurones pt3:

  • so it'll take less of a stretch of spindle before action potentials are generated as tensioning of the spindle through gamma motor neurones makes the spindle more sensitive