What is the difference between a muscle’s origin and its insertion? How are the muscles of facial expression different from most other muscles?How do respiratory muscles function to produce breathing?What are the rotator cuff muscles? What are the functions of the rotator cuff?Describe the structural and functional relationship between neurons and skeletal muscle fibers. What is an action potential and which ions are involved?How does a muscle fiber generate tension through crossbridge cycling and why does an increase in calcium ions cause muscle contraction?Compare and contrast three types of muscle contraction. How does a muscle fiber change with endurance training, resistance training, and disuse?