skeletal muscle contraction Flashcards

1
Q

what is a motor neuron

A
  • a nerve cell which conducts a nerve impulse to a group of muscle fibres
  • specialised cells which transmit nerve
    impulses rapidly to a group of muscles.
  • Cell body in the brain or spinal cord with an extending axon which
    branches to connect motor end plates to a group of muscles fibres.
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2
Q

what is a motor unit

A

a motor neuron and the muscle fibre stimulated by its axon

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3
Q

what is a motor units function

A

to carry nerve impulses from the brain + spinal cord to the muscle fibres, initiating muscular contraction

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4
Q

what is a neurotransmitter

A

a chemical (acetylcholine) produced and secreted by a neuron which transmits the nerve impulse across the synaptic cleft to the muscle fibre

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5
Q

what is the all-or-none-law

A
  • depending on whether the stimulus (action potential) is above a threshold, all muscle fibres will give a comply contraction or no contraction at all
  • in order for a contraction to occur, all the muscle fibres must be ready to contract or no contraction will happen
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6
Q

what is the process of the motor unit + skeletal muscle contraction

A
  • skeletal muscle can only contract when stimulated by an electrical impulse sent from the CNS
  • Motor neurons are the specialised cells which transmit nerve impulses rapidly to a group of muscles
  • Cell body in the brain or spinal cord with an extending axon which branches to connect motor end plates to a group of muscles fibres
  • Sending the nerve impulse to the muscle fibres is an electrochemical process which relies on a nerve action potential to conduct the nerve impulse as an action potential cannot cross the synaptic cleft without a neurotransmitter
  • If enough neurotransmitter is secreted, electrical charge will surpass the threshold, muscle action potential is created
  • This action potential creates a wave of contraction down the muscle fire - all muscle fibres will contract at the same time with maximum force
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7
Q

what is the process of the motor unit + skeletal muscle contraction (shorter/condensed)

A
  • Nerve impulse initiated in the motor neuron cell body
  • Nerve impulse conducted down the axon of the motor neuron by a nerve action potential to the synaptic cleft
  • Neurotransmitter called acetylcholine is secreted into the synaptic cleft to conduct the nerve impulse across the gap
  • If the electrical charge is above a threshold, the muscle fibre will contract
  • This is an ‘all or none’ fashion
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8
Q

What is the effect of stimulating more motor units?

A

Increased strength / force of contraction

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9
Q

small motor neurons features

A
  • Stimulate few small muscle fibres
  • Small & slow amount of force
  • Fatigue resistant
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10
Q

large motor neurons features

A
  • Stimulate many large muscle fibres
  • Large amounts & rapid forces
  • Fatigue quickly
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