Muscle and movement. Illustration of human muscle anatomy and movement systems. Movement depends on the interaction of multiple systems in the body,including muscle,bones and joints,nervous co- ordination and balance. The human body (at centre,posterior view) contains some 600 muscles,most of which are skeletal (voluntary) muscles under con- scious control. A skeletal muscle is seen at top right,with its internal fibres and nerve attach- ment (yellow). At top left,specialized regions of the brain co-ordinate movement,with the aid of the spinal cord and its nerve branches (bottom right). Joints,as at the knee (bottom left),give bones mobility as the muscles act upon them |