https://wiki.pathfindersonline.org/index.php?action=history&feed=atom&title=Translations%3AAY_Honors%2FBones%2C_Muscles%2C_and_Movement%2FAnswer_Key%2F73%2FenTranslations:AY Honors/Bones, Muscles, and Movement/Answer Key/73/en - Revision history2026-04-19T10:42:18ZRevision history for this page on the wikiMediaWiki 1.35.5https://wiki.pathfindersonline.org/index.php?title=Translations:AY_Honors/Bones,_Muscles,_and_Movement/Answer_Key/73/en&diff=358358&oldid=prevFuzzyBot: Importing a new version from external source2021-02-15T21:34:06Z<p>Importing a new version from external source</p>
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<!-- 15. Describe the process that causes a muscle to contract. --><br />
[[Image:Skeletal_muscle.jpg|800px]]<br />
# When the muscle is in a resting state, thin strands of a protein called tropomyosin are wrapped around the actin filaments, blocking the myosin binding sites. This keeps the myosin from binding to actin.<br />
# Molecules called troponin are attached to the tropomyosin.<br />
# When calcium is introduced into the muscle cell, calcium ions bind to troponin molecules.<br />
# Calcium then pulls troponin, causing tropomyosin to be moved as well, therefore causing the myosin binding sites on the actin to be exposed.<br />
# Myosin binds to the now-exposed binding sites.<br />
# As soon as the myosin head binds to actin, the head bends at its hinge.<br />
# Once the head bends, the myosin loses energy, and remains attached to the actin.<br />
# When re-energized by adenosine triphosphate (ATP), the myosin head detaches from the actin filament, and is ready to attach and bend again.<br />
# The collective bending of numerous myosin heads (all in the same direction), combine to move the actin molecules closer together. This results in a muscle contraction.</div>FuzzyBot