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16 Terms

1
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what can muscles do

  • be stimulated by a nerve impulse

  • shorten in length

  • be stretched

  • return to their original length

2
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sliding filament theory

  • as the thin actin and thick myosin filaments slide over one another, the Z-lines are drawn closer together and the sarcomere is shortened

  • this results in shortening of the muscle fibres and shortening of the whole muscle

  • ATP is required for the shortening of muscle fibres

<ul><li><p>as the thin actin and thick myosin filaments slide over one another, the Z-lines are drawn closer together and the sarcomere is shortened</p></li><li><p>this results in shortening of the muscle fibres and shortening of the whole muscle</p></li><li><p>ATP is required for the shortening of muscle fibres</p></li></ul><p></p>
3
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steps of the sliding filament theory

  1. Nerve impulse reaches the muscle fibre, triggering release of Ca²⁺ from the sarcoplasmic reticulum.

  2. The calcium binds to the actin myofilaments and this causes the myosin binding sites to be exposed to the myosin.

  3. The myosin myofilament joins to the myosin binding sites on the actin and forms crossbridges.

  4. The formation of crossbridges requires energy (ATP).

  5. The myosin crossbridges pull on the actin and the actin slides over the myosin (note: myosin doesn’t change in length). This also requires ATP and is the muscle-shortening phase of muscular contraction. This is called downstroke.

  6. Z-lines move close together / sarcomere shortens.

  7. It requires ATP to cause the myosin to “unhook” off the binding sites. Once the crossbridges move off the binding sites, the actin slides back to the “resting” position. Z-lines move further apart / sarcomere lengthens.

<ol><li><p>Nerve impulse reaches the muscle fibre, triggering release of Ca²⁺ from the sarcoplasmic reticulum.</p></li><li><p>The calcium binds to the actin myofilaments and this causes the myosin binding sites to be exposed to the myosin.</p></li><li><p>The myosin myofilament joins to the myosin binding sites on the actin and forms crossbridges.</p></li><li><p>The formation of crossbridges requires energy (ATP).</p></li><li><p>The myosin crossbridges pull on the actin and the actin slides over the myosin (note: myosin doesn’t change in length). This also requires ATP and is the muscle-shortening phase of muscular contraction. This is called downstroke.</p></li><li><p>Z-lines move close together / sarcomere shortens.</p></li><li><p>It requires ATP to cause the myosin to “unhook” off the binding sites. Once the crossbridges move off the binding sites, the actin slides back to the “resting” position. Z-lines move further apart / sarcomere lengthens.</p></li></ol><p></p>
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tendons

attaches muscle to the bones of the skeleton by fibrous, inelastic connective tissue

<p>attaches muscle to the bones of the skeleton by fibrous, inelastic connective tissue</p>
5
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can muscles push bones apart

no

muscles can only contract

meaning that they pull bones together but cannot push them apart

<p>no</p><p>muscles can only contract</p><p>meaning that they pull bones together but cannot push them apart</p>
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antagonistic pairs

  • Agonist: muscle doing the work (e.g., biceps).

  • Antagonist: muscle relaxing (e.g., triceps).

<ul><li><p>Agonist: muscle doing the work (e.g., biceps).</p></li><li><p>Antagonist: muscle relaxing (e.g., triceps).</p></li></ul><p></p>
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other roles

  • Synergists: assist the agonist.

  • Fixator: stabilise origin of prime mover.

<ul><li><p>Synergists: assist the agonist.</p></li><li><p>Fixator: stabilise origin of prime mover.</p></li></ul><p></p>
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origin

the end of a muscle that is fixed to the stationary bone

<p>the end of a muscle that is fixed to the stationary bone</p>
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insertion

  • the end of a muscle fixed to the moveable bone

  • During contraction, the insertion is pulled toward the origin.

<ul><li><p>the end of a muscle fixed to the moveable bone</p></li><li><p>During contraction, the insertion is pulled toward the origin.</p></li></ul><p></p>
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belly

  • The thick, fleshy middle part of the muscle between the origin and insertion.

  • this is the part that contracts and generates movement.

<ul><li><p>The thick, fleshy middle part of the muscle between the origin and insertion.</p></li><li><p>this is the part that contracts and generates movement.</p></li></ul><p></p>
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types of muscle contraction

  • concentric

  • eccentric

  • isometric

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concentric

  • muscle shortens

  • for example; Lifting phase of bicep curl

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eccentric

  • muscle lengthens

  • for example; lowering phase of bicep curl

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isometric

  • no change

  • static

  • for example; Holding a weight steady, plank

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muscle tone

  • maintaining partial contraction of skeletal muscles

  • some muscle fibres are contracted while others are relaxed

  • The fibres relieve one another so smoothly that the contraction can be kept up for long periods of time

  • muscle tone holds many of our body parts in position

    • eg; our head is help up by the partial contraction of neck muscles

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posture

the way a person holds they body when standing or sitting