Neuromuscular system

• What is a motor unit ?

  A motor unit consists of a single motor neurone and all the muscle fibres supplied by that neurone
• what is a motor neurone ?

  nerve cells which transmit the brains instructions through electrical impulses to the muscles
• what is a neuromsucular junction?

  where the motor neuron and muscle fibres meet
• The number of muscle fibres within a motor unit depends on the degree of accuracy or power required

  • As few as 5 muscle fibres joined to one motor neurone provides precision ,accuracy and fine control
  • AS many as 1000 muscle fibres joined to one motor neurone provides force and power
• how to vary force of contraction within motor unit recruitment

  Think FAST

  Frequency

  Amount

  Size

  Type
• frequency- recruiting motor units via wave or spatial summation

  • spatial summation -some motor units are contracting whilst others are relaxing , ATP consumption and workload is shared across the motor units , fatigue is evenly distributed , used in prolonged endurance based events
  • wave summation-the motor unit is flooded with electrical impulses , the next impulse arrives before the motor unit has had ice to relax , the accumulation of impulses lead to a tectopic contraction which produces maximal force
• `Amount- recruiting more or fewer motor units

  • for more power and force -more motor units recruited
  • for less force and more accuracy and precision-less motor units recruited
• Size- recruiting smaller or larger motor units

  • recruit smaller motor units for smaller force and accuracy
  • recruit larger motor units for stronger force and power
• type - the type of motor unit recruited

  • recruit fast twitch motor units for greater force and faster speed of contraction
  • recruit slow twitch motor units for smaller and slower speed of contraction
• type 1 fibres slow twitch

  • small motor neurone = slow impulse
  • slow impulse = slow sped of contraction
  • slow contraction = low force
  • high mitochondria, myoglobin and triglyceride stores
  • low pc stores
  • high aerobic capacity
  • delays fatigue
• type 11a fast oxidative glycolytic

  • large motor neurone = fast impulse
  • fast impulse = fast speed of contraction
  • fast contraction = high force
  • medium triglyceride , mitochondria ,myoglobin and pc stores
  • high glycogen stores
  • medium to high anaerobic capacity
  • medium aerobic capacity
  • some resistance to fatigue
• type 11x fast twitch glycolytic

  • large motor neurone =fast impulse
  • fast impulse = fast speed of contraction
  • fast contraction= high force
  • high glycogen , pc and atp stores
  • low myoglobin and mitochondria stores
  • high anaerobic capacity
  • fatigues easily