The Muscular System
	u The Striated Muscle (those responsible for voluntary movements) l Anatomy - Two types of fibers u Extrafusal Fiber: these fibers do the work of the muscle. u Intrafusal Fiber or Muscle Spindle: controls muscle tone and provides important sensory information. l Contraction u Controlled by the nervous system u Muscles only shorten (i.e., only go one direction) u Organized in opposition pairs.