Paul Andersen explains the three types of muscle found in humans; striated, smooth and cardiac muscle. He explains how actin and myosin interact to contract the sarcomere in a muscle. The sliding filament theory explains how ATP and calcium are used to contract the z disks. Intro Music Atribution Title: I4dsong_loop_main.wav Artist: CosmicD Link to sound: http://www.freesound.org/people/CosmicD/sounds/72556/ Creative Commons Atribution License