MUSCLE ACTION

how?

when?

what?

What's going on when you curl that dumbell?

• When a muscle is stimulated to contract, calcium attaches to an actin microfilament troponin, which displaces tropomyosin. Tropomyosin is like a chaperone covering the binding site for large muscle fibers to connect and contract.
• Because the shape, the configuration, of the filaments alter, the large muscle filaments, myosin, can bind to smaller actin filaments. Now, threadlike fibers of muscle, much like the strings of a potroast, can cross over one another,shortening the entire muscle mass.
• As the muscle fibers form cross bridges, the insertion moves closer to the origin. In other words, the dumbell is pulled towards the shoulder.
• With the nervous system sending signalsto contract the biceps muscles, the triceps are "told" to relax. This prevents antagonistic rigidity.
• When the brain stops signalling contraction, calcium is reuptaken by the muscle cells. Then, crossbridges detach the muscle lengthens, and the arm lowers the dumbell.

  CATEGORY	SKELETAL MUSCLE ACTION
  extensor	increases the angle at the joint
  flexor	decreases the angle at the joint
  abductor	moves limb away from the midline of the body
  adductor	moves limb towards midline of the body
  levator	moves insertion upward
  depressor	moves insertion downward
  rotary	rotates bone along its axis

  

  Glossary

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