Lecture 8: muscle mechanics Flashcards

1
Q

how is the length tension relationship constructed?

A
  • it is constructed by varying the muscle length at rest and then measuring the isometric tension when the muscle is maximally stimulated at that length
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2
Q

Describe the length tension curve of skeletal muscle

A
  • as the length of the sarcomere is shorter, the tension is low
  • as the sarcomere gets stretched - it gets to a point in which the tension produced is maximal - optimal length
  • skeletal muscle is usually near the optimal lnegth
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3
Q

what is an isolated contraction of a skeletal muscle called and how is it developed?

A
  • a single AP from a motor neuron will produce a single contraction in the muscle fibres innervated by the motor neuron
  • the isolated contraction is called a** twitch**
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4
Q

what does clostridium tetani infections cause and how do they do this?

A
  • clpstridium tetani infections cause tetanus - where there uncontrollable spasms of the muscle
  • the toxin blocks inhibitory synapses in the CNS - which causes increased activity of the motor nerves to the sksletal muscle
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5
Q

what is twitch summation?

A
  • if a muscle fiber is restimulated before it has completely relaxed, the** second twitch is added onto the first twitch**, resulting in a summation
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6
Q

what is a tetanus in terms of muscle contractions?

A
  • if a muscle fibre is stimulated so rapidly that it does not have time to relax between all the stimuli - a maximal sustained contraction known as a tetanus occurs
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7
Q

compare unfused tetanus and complete tetanus contraction

A
  • summation can lead to unfused tetanus - the **stimuli are far enough apart **to **allow muscle to relax slightly **between stimuli
  • summation can also lead to complete tetanus- muscle reaches steady contraction - doesnt relax until fatigue hits
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8
Q

how long does the action potential of a skeletal muscle last for?

A
  • 5 milliseconds
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9
Q

if a skeletal muscle AP lasts for 5ms, how many times can a muscle be activated per second?

A

more than 200 times per second

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10
Q

Describe the staircase phenomenon (treppe) with regards to muscle contraction

A
  • when a muscle is** stimulated repetitvely** at a frequency** below which causes summation, there is a progressive increase in the tension **developed with each twitch **until a max twitch is developed **
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11
Q
A
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