We're kicking off our exploration of muscles with a look at the complex and important relationship between actin and myosin. Your smooth, cardiac, and skeletal muscles create movement by contracting and releasing in a process called the sliding filament model. Your skeletal muscles are constructed like a rope made of bundles of protein fibers, and that the smallest strands are your actin and myosin myofilaments. Its their use of calcium and ATP that causes the binding and unbinding that makes sarcomeres contract and relax. Table of Contents Smooth, Cardiac, and Skeletal Muscles Create Movement 1:18 Sliding Filament Model 4:52 Skeletal Muscles Are Made of Bundles of Protein Fibers 2:40 Actin and Myosin Myofilaments 3:54 Calcium and ATP Cause the Binding and Unbinding 5:05 *** Crash Course is now on Patreon! You can support us directly by signing up at http://www.patreon.com/crashcourse Thanks to the following Patrons for their generous monthly contributions that help keep Crash Course free for everyone forever: Mark Brouwer, Jan Schmid, Steve Marshall, Anna-Ester Volozh, Sandra Aft, Brad Wardell, Christian Ludvigsen, Robert Kunz, Jason, A Saslow, Jacob Ash, Jeffrey Thompson, Jessica Simmons, James Craver, Simun Niclasen, SR Foxley, Roger C. Rocha, Nevin, Spoljaric, Eric Knight, Elliot Beter, Jessica Wode ***SUBBABLE MESSAGES*** TO: SEM students FROM: Mrs. S You are confident and courageous! I believe in you! DFTBA! -- TO: Zachary FROM: She who gave you life! You, like the Mongols, will always be the exception. ***SUPPORTER THANK YOU!*** Thank you so much to all of our awesome supporters for their contributions to help make Crash Course possible and freely available for everyone forever: David Rybka, Beth Larter, Damian Shaw, Randy Goldberg MD, Cynthia Krohn, Allison DeVoe, Brinae Lois Gaudet, Sara Bovi, Stephen DeCubellis, Travis Bell -- Want to find Crash Course elsewhere on the internet? Facebook - http://www.facebook.com/YouTubeCrashCourse Twitter - http://www.twitter.com/TheCrashCourse Tumblr - http://thecrashcourse.tumblr.com Support Crash Course on Patreon: http://patreon.com/crashcourse CC Kids: http://www.youtube.com/crashcoursekids