Motor units

  • Created by: cara12
  • Created on: 15-04-19 10:44
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  • Motor units
    • A motor neuron plus all the muscle fibres it innervates
      • To carry out impulses from the central nervous system to the muscle fibres to initiate muscular contraction
    • Summarising role of motor unit
      • 1.Nerve impulse initiated in the motor neuron cell body
      • 2.Nerve impulse conducted down the axon of the motor neuron by a nerve action potential to the synaptic cleft
      • 3.Neurotransmitter called acetylcholine is secreted into the synaptic cleft to conduct the nerve impulse across the gap
      • 4.If the electrical charge is above threshold,the muscle fibre will contract
      • 5.'All or none law' fashion
    • Axon carries the electrical impulse from the cell body to neuromuscular junction.
    • Neuromuscular Junction-The point where motor neuron communicates with muscle fibre across a space called the synapse
    • Synapse-The space between a motor neuron and skeletal muscle
    • Motor end plate-The area of muscle fibre that establishes synaptic contact with motor neurone
    • 1.Resting potential-The neuron at rest.There is lower charge inside the neuron than outside
    • 2.Action potential-The electrical activity carried down the axon.
    • 3.Neurotransmitter-Chemical messenger that transmits across synapse and binds to muscle fibres to initiate contraction
    • 4.Acetylcholine-The neurotransmitter released at neuromuscular junction that travels across synapse
    • 5.All or none law-If the action potential threshold is reached,all muscle fibres in the motor unit are activated.
      • If it is not reached,no muscle fibres are activated.


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